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A review of the temperate broad-leaved evergreen forest zone of Southeastern North America: floristic affinities and arborescent vegetation types.

 I. Abstract
 II. Introduction
 III. Application of Walter's Classification of Ecological Systems
 IV. Review of the Atlantic and Gulf Coastal Plains Floristic Province
 and Recognition of Subprovinces
 A. The Apalachicolan Subprovince
 B. The Central Floridian Subprovince
 V. Review of Central Floridian Subprovince Vegetation: The Temperate
 Broad-Leaved Evergreen Forest Zone (Zonobiome V and
 Zonoecotones V/II and V/VI)
 A. General
 B. Classification and Description of Central Floridian Vegetation
 Types
 1. Biogeocenes of Zonobiome V and Zonoecotones V/II and V/VI
 a. Broad-Leaved Evergreen Forests
 b. Live Oak Dune Forests
 c. The Magnolia grandiflora--Ilex opaea Association
 d. The Sabal palmetto--Quercus laurifolia-Q, nigra Q.
 virginiana-Liquidambar Association
 e. Quereus virginiana Sabal palmetto-Tropical Hardwoods
 f. Evergreen Oak-Holarctic Deciduous Hardwoods
 2. Biogeocenes of Pedobiome V and Pedoecotones V/II and V/VI
 a. Scrub
 b. The Pinus elliottii van elliottii Association
 c. Mixed Pine Woodlands
 d. South Florida Slash Pine Flatwoods
 e. Mixed "Bay" Forests
 f. The Sabal palmetto Association
 g. The Pinus serotina/Lyonia lucida Association
 h. Pond Cypress "Domes".
 i. Maritime Shrub and Scrub Forest Communities
 C. Related Vegetation in the Gulf Region of Louisiana and Texas
 1. Cheniers
 2. The Texas Gulf Coastal Prairie
 D. Related Flora and Vegetation in the Greater Antilles
 1. Cuba and Jamaica
 a. Live Oaks Tropical Hardwoods-Pines
 b. Tropical Pine Forests
 c. Montane and Upper Montane Forests and Shrublands
 2. South Florida and the Bahamas
 3. Puerto Rico
 E. Related Vegetation in Baja California Sur, Mexico
 VI. Conclusions
 VII. Acknowledgments
VIII. Literature Cited


II. Introduction

The Temperate Broad-Leaved Evergreen Forest (TBEF) zone is centered in peninsular Florida. It is characterized by mainly nontropical taxa that form an evergreen dicot forest, often with a Sabal palm in the canopy, in which deciduous dicot trees are present but rarely become local dominants (Greller, 1989). Dominant evergreen taxa (cf. Godfrey, 1988) in the canopy are Quercus virginiana, Q. hemisphaeriea, Magnolia grandiflora and Sabal palmetto. Other evergreens are Gordonia lasianthus and Persea borbonia (on wetter sites). Fieus aurea is common in south central and southeastern Florida. Quercus hemisphaerica, Q. nigra and Q. laurfolia are oaks that are usually at least partially winter green (Godfrey, 1988). Deciduous dominant taxa are Liquidambar styraciflua and Carya glabra. Conifers such as Pinus elliottii (on acidic, sandy sites), Juniperus silicicola (in openings on calcium-rich sites) and Pinus meda (on disturbed sites) may enter the canopy. Lianas are well developed and include members of the Bignoniaceae, Cactaceae (coastal), Smilacaceae and Vitaceae. Epiphytic Bromeliaceae and Polypodiumpolypodioides are also common. The shrub palm Serenoa repens and evergreen dicot shrubs including Ilex vomitoria, Myrica cerifera, Vaccinium arboreum and other Ericaceae often dominate the understory. Between the shrubs only litter covers the soil, with some scattered herbs such as Oplismenus and Chasmanthium (grasses) as well as Mitchella repens on fertile sites, Panicum and Andropogon, and Lechea, Cassia and Desmodium (Laessle, 1942). The cycad Zamiapumila, which occurs in the herb layer on calcareous soils, reaches its northern limit in North America in this forest zone.

For the present study, I recognize the TBEF (Greller, 1980, 1989) zone as extending over three physiographical regions: Peninsular Florida (including Atlantic and Gulf Coastal regions); the Atlantic Outer Coastal Plain, Sea lslands and Outer Banks (continuous north to North Carolina); and the Gulf [of Mexico] Coastal shores and islands, prairies and marshes (panhandle Florida, adjacent Alabama, Louisiana and Texas).

III. Application of Waiter's Classification of Ecological Systems

Heinrich Walter (1985) provides a system for classifying world vegetation. He recognizes a "geo-biosphere" comprising terrestrial ecosystems and a "hydro-biosphere" for aquatic ecosystems. In the geobiosphere, he uses the prevailing climate as the primary independent factor and recognizes nine latitudinal climate zones that he designates ecologically as "zonobiomes" (ZB). Zonobiomes are large and climatically uniform environments. "Zonal" soil types and vegetation types correspond to these zonobiomes. For example, ZB I is "Equatorial with diurnal climate, humid." Within this climate a zonal soil type develops, "Equatorial brown clays (ferralitic soils, latosols)." The corresponding zonal vegetation is listed as "Evergreen tropical rain forest." Other important zonobiomes in the present study are ZB II (tropical deciduous forest or savanna), ZB V (temperate evergreen forest), ZB VI (broad-leaved winter-deciduous forest) and ZB VII (steppe to desert with cold winters).

Walter recognizes that zonobiomes are not sharply defined but form broad transitions, which he calls "zonoecotones" (ZE). These are designated according to the zonobiomes they link: e.g., ZE I/II, ZE II/III; they may include three zonobiomes. Because of the presence of mountains, the geobiosphere can be divided vertically as well as horizontally.

Mountains produce climates and vegetation that differ from the zones from which they arise. Walter terms such mountainous environments "orobiomes" (OB) and subdivides them into altitudinal belts. The orobiomes are distinguished according to the zonobiome to which they belong: OB I, OB II, etc.

Where substrates exist that produce extreme types of soil and vegetation, Walter recognizes "pedobiomes." ZBs are areas where soil conditions are "'moderate, neither too light nor too heavy, and thus allow slow penetration of the soil by precipitation. Rather extreme substrates produce soil types that may be warmer and drier than the regional climate (chalky soils), or may contain salts that are harmful to vegetation, or may be extremely poor in nutrients. "The vegetation of the pedobiomes is influenced to a greater extent by the soil than by the climate, so the same vegetational forms may occur in a number of zones." This vegetation is termed "azonal." Pedobiomes are designated according to soil type: lithobiomes (stony soil), psammobiomes (sandy soils), halobiomes (salty soils), helobiomes (moor or swamp soils), hydrobiomes (soils covered with water), peinobiomes (soils poor or deficient in nutrients), amphibiomes (temporarily wet soils), etc. (Walter, 1985). Such extreme sites often occupy large areas. In Florida, siliclastic deposition originating in the uplands to the north, and ranging in depth from less than a meter to more than 300 m (Randazzo & Jones, 1997), has enabled the extensive development of psammobiomes (e.g., pine flatwoods) and peinobiomes (e.g., scrub). Associated with these extremely sandy and nutrient poor soils are areas of impermeable limestone bedrock that permit the formation of helobiomes (i.e., pond cypress domes) and hydrobiomes (e.g., everglades and bald cypress swamps).

For the classification of the Florida Hydro-Biosphere the reader is referred to "Brief Descriptions of Natural Communities: Palustrine, Lacustrine, Riverine, Subterranean and Marine/Estuarine" of the Florida Natural Areas Inventory (1998). Kautz et al. (1993) records 22 land-cover types from LANDSAT Thematic Mapper imagery, dated 1985-1989. Their table 2 gives the area of each type in hectares and the percentage cover by uplands, wetlands and disturbed types of land.

Reviewing Greller (1980, 1989), we can recognize at least one zonobiome and two zonoecotones (cf. Walter, 1985) for the TBEF region. These may be designated ZB V, ZE V/II and ZE V/VI. They are, respectively, the central TBEF in peninsular Florida, the TBEF transition to the Tropical Semi-Deciduous Woodland (TF) of South Florida, and the TBEF transition to the Southern Mixed Hardwood Forest (SMHF) Association (DEC, Deciduous-Evergreen-Conifer zonoecotone of Greller, 1989). These zonobiomes and zonoecotones are delineated in Figure 1. SMHF, which should be designated ZE VI/V, occupies the majority of the Outer Coastal Plains of the southern United States, including the northern half of the Florida panhandle (SMHF is not shown in Figure 1). Monk (1965) earlier described forest vegetation in north central Florida, noting that evergreen live oak forests were better developed toward the east.

[FIGURE 1 OMITTED]

ZB V extends from Lee, Hendry, and western Palm Beach Counties in south central Florida north roughly to a line connecting Pasco to eastern Duval and Nassau Counties, then north along the Atlantic Coast to Smith Island, North Carolina (arrow in Figure 1). It also extends north and west from Pasco County along the Gulf Coast on the mainland and Gulf islands of the Florida panhandle. ZB V is confined to and poorly represented on the barrier islands in Alabama; it may be absent from Mississippi Gulf islands (arrow in Figure 1).

ZE V/VI occurs from northern Florida landward of ZB V north along the Atlantic Coast to Cape Hatteras, North Carolina, with an outlier in Virginia Beach, Virginia (cf. Ware et al., 1993). It extends westward in a narrow band along the coast on the mainland of the Florida panhandle and continues westward on the coastal fringe of Alabama and possibly Mississippi. TBEF is represented by clusters of live oak and dwarf palmetto along the natural levees and in the coastal marshes of southern Louisiana (Brown, 1976). In Texas, TBEF is represented along the coastal plain, in the Gulf Prairies and Marshes vegetational region (Simpson, 1988: 24). North to south, the dominants of the coastal tree islands are Quercus virginiana (Jefferson to Brazoria Counties), Quercus virginiana x Q. fusiformis (Brazoria to Refugio and Aransas Counties), Q. minima x Q.fusiformis (Victoria and Calhoun Counties), and Q. fusiformis x Q. oleoides (Aransas to Kenedy Counties; Simpson, 1988, plate 15). Texas Parks and Wildlife (1984) mapped Live Oak Woods / Parks (Quercus virginiana), in Aransas County and on the southern part of the Rio Grande Plains, throughout Brooks and Kenedy Counties. It is not certain in which, if any, of the preceding zonobiomes or zonoecotones to classify the live oak groves in the Chenier and Texas Coastal Prairie regions. These may better be treated as pedobiomes or pedoecotones.

SMHF (ZE VI/V) in Florida extends from the eastern third of Madison County west through Jefferson, Leon and Gadsden Counties. The border of SMHF dips south into Liberty and Calhoun Counties only along the Apalachicola River, then west again, including all of Jackson County, the northern half of Washington County, all of Holmes County, and the northern two-thirds of Walton, Okaloosa, Santa Rosa and Escambia Counties. In comparing number of life forms, SMHF, which is listed as "Deciduous Dicot / Evergreen Dicot / Conifer" (DEC) life zone in Greller (1989, table 2), has representative taxa in 20 categories, with TBEF having taxa in 17 categories. Thus, it can be argued that physiognomically SMHF is the richest life zone in eastern North America, and likely the richest in all of North America north of Mexico. Kurz (1938, 1944), working in the Apalachicola River valley and the Red Hills in the vicinity of Tallahassee, records upland forests on mesic sites as having at least 32 canopy, subcanopy and small tree species; 9 shrubs, 2 epiphytes; 13 vines or lianas; and numerous herbs, including dicots, lilioid and graminoid monocots, and ferns. Such local floristic richness may be unequaled in all of North America.

It is the purpose of the present article to review the literature on Florida plant endemism, especially as it relates to the TBEF zone as represented in peninsular Florida. Based on this review, 1 propose the recognition of a Central Floridian Subprovince in the Atlantic and Gulf Coastal Plains Province of southeastern North America (cf. Greller, 2000). Further, I present a comprehensive classification for the ligneous vegetation in the subprovinee and touch on similar vegetation in the Greater Antilles and the Sierra de la Laguna in Baja California Sur, after a review of the relevant literature. I also argue for the recognition of an Apalachicolan Subprovince, centered on the panhandle of Florida and extending from southwestern Georgia to Louisiana, mainly in the Southern Mixed Hardwoods Forest zonoecotone. No attempt has been made to synonymize the taxa listed by various authors.

IV. Review of the Atlantic and Gulf Coastal Plains Floristic Province and Recognition of Subprovinces

Greller (2000) recognizes the Atlantic and Gulf Coastal Plains Floristic Province as one of two provinces in a proposed "Southeastern North American Region" of the Madrean Subkingdora of the Holarctic Kingdom (cf. Takhtajan, 1986). The other province was designated "Mexican Mountains" and comprised the "Sierra Madre Oriental-Serranias Meridionales-Serranias Transistemicas." It is likely that a third province can be recognized for the Upper Montane Zone of the Greater Antilles and the Caribbean Basin.

Randazzo and Jones (1997, 67) summarized the history of deposition and erosion of the Florida peninsula. They noted that "carbonate sedimentation dominated deposition ... since the mid-Mesozoic ... [despite periodic] pulses of siliclastic sediments from the north [which] suppress[ed] carbonate deposition ... [on] the entire Florida platform.., by the middle to late Pliocene. Miocene to Holoeene sediments cover virtually the entire Florida platform, leaving only limited exposures of older sediments.

"Sea-level fluctuations ... [include] a major regression during the late Oligocene [followed by a sea level rise] during the Early and Middle Miocene ... [when] the entire Florida Platform [was under water].... Sea level fell during the Late Miocene, exposing much of the platform. ... [The] sea ... covered much of the platform during the Early Pliocene. Late Pliocene sea level was significantly lower ... [although still] sub-aerial.... Pleistocene sea level did not rise higher than approximately 20 m above the present level.... Following the latest Pleistocene regression, sea level has risen during the Holocene to its present position. Holocene sediments form the present coastline ... beach, dune, marsh, and lagoon environments."

Taxa representing tropical, warm-temperate and deciduous forest floras have been present in the general region since the Early Tertiary, and likely on the Florida Platform in late Oligocene and again in Late Miocene. Progressive cooling since the Eocene, culminating with the deep penetration of Pleistocene ice sheets into central North America, eliminated all but the deciduous flora and some broad-leaved evergreens. These taxa persisted in the Mississippi Valley and on a shortened Florida peninsula (Platt & Schwartz, 1990; Randazzo & Jones, 1997, 3, fig. 5.6).

Takhtajan (1986) classifies the flora of the region in the Atlantic and Gulf Coastal Plain Province of the North American Atlantic Region of the Boreal Subkingdom of the Holarctic Kingdom. Most of the plants occur in all or parts of a U-shaped area coinciding with the Atlantic and Gulf Coastal Plains and extending northward in the Mississippi Valley to Indiana. Takhtajan includes all but the southern tip of Florida in the province.

Many species are endemic both to the Appalachian Province of Takhtajan (1986) and to his Gulf and Atlantic Coastal Plains Province, including Liriodendron tulipifera, Carpinus caroliniana, Fagus grondifolia, some Quercus spp., Carya spp., Nyssa sylvatica, Cornus florida and Chionanthus virginicus. Others are confined to the southern part of the Appalachian Province and to the latter: Castanea pumila, Bumelia lycioides, Acer barbatum, A. leucoderme, Toxieodendron vernix and Aralia spinosa (Takhtajan, 1986).

Sorrie and Weakley (2001) undertook a complete inventory of endemic vascular plants in the Atlantic and Gulf Coastal Plains physiographical region. Their area of concern encompasses vegetation ranging from near-Boreal, conifer-dominated types in Nova Scotia, to Sonoran thornshrubs in Tamaulipas, Mexico. In the geographic area that comprises the Southern Mixed Hardwood Forest ZE and Temperate Broad-Leaved Evergreen Forest ZB (cf., Greller, 1989), Sorrie and Weakley recognized two regions based on endemism: "southern South Carolina to peninsular Florida, no. 6" (TBEF) and "Longleaf pine, no. 18" (SMHF). The latter extends from southeastern Virginia to central Florida to eastern Texas, thus including parts of the OakPine Region of the Deciduous Forest ZB.

Within TBEF (number 6), Sorrie and Weakley (2001) recognized two subdivisions: "southeastern Georgia to northeastern Florida, no. 7" and "Lake Wales Ridge, no. 8." Within SMHF (number 18), they recognized the "East Gulf Coastal Plain, no. 10" as a center of endemism. Within number 10, they recognized two sub-divisions: "central panhandle of Florida, no. 11" and "western panhandle of Florida and adjacent Alabama, no. 12." In addition, along the Gulf Coast from western Louisiana to eastern Tamaulipas, they recognized as an area of endemism the "West Gulf coastal prairies and dunes, no. 15."

Sorrie and Weakley (2001) recognized "Subtropical Florida, no. 9" (Florida south of Lake Okeechobee) as an area of coastal plains endemism. Clearly, flora in South Florida is related to that of the West Indies and not to the temperate forest zones of North America. Further, they recognized two areas of endemism disjunct between the southeastern United States and the West lndies. These are number "24, widespread, disjunct to western Cuba" and number "25, widespread, disjunct to the Bahamas." In both cases, western Cuba and (the northwestern islands of) the Bahamas, the endemic taxa of the coastal plains are centered on the Florida peninsula. This floristic relationship occurs within another floristic region, the West Indian.

The Atlantic and Gulf Coastal Plains province has as endemics 2 families (Dionaeaceae and Leitneriaceae, both monotypic), 47 genera (72% monotypic), 1306 (of some 6000 total) species and 297 subspecies and varieties (Sorrie & Weakley 2001). Among the endemic species are the following trees and shrubs: Taxus floridana, Torreya taxifolia, Pinus elliottii, P. glabra, P. palustris, P. serotina, Taxodium distiehum, Persea borbonia, P. palustris, Illicium floridanum, L parviflorum, Planera aquatica, Quercus arkansana, Q. falcata, Q. hemisphaerica, Q. incana, Q. laevis, Q. laurifolia, Q. michauxii, Q. myrtifolia, Q. nuttallii, Q. pagodaefolia, Q. schumardii Carya aquatica, Franklinia alatamaha (extirpated), Gordonia lasianthus, Lyonia ferruginea, Bumelia tenax, Halesia diptera, Prunus caroliniana, Gleditsia aquatica, Ilex amelanchier, L coriacea, I. myrtifolia, Nyssa ogeche, N. sylvatica [var. biflora], Fraxinus caroliniana, Viburnum obovatum and Serenoa repens. Other interesting endemics or near endemics are Schisandra [glabra], Sarracenia spp., Dionaea muscipula, Asclepias spp., Conradina spp., Pinckneya [bracteata], Yucca gloriosa, Iris hexagona, Xyris spp. and Lachnocaulon spp. Leitneria floridana is a monotypic species in the endemic Leitneriaceae.

I propose that both the East Gulf Coastal Plain centered on the Apalachicola River (Apalachicolan) and peninsular Florida north of Dade and Monroe Counties (Central FIoridian) be treated as separate subdivisions of the Atlantic and Gulf Coastal Plain Province of the Southeastern North American Region of the Madrean Subkingdom of the Holarctic Kingdom. In the discussion that follows, those phytochoria are so designated.

A. THE APALACHICOLAN SUBPROVINCE

Sorrie and Weakley (2001) list two endemic genera for their "East Gulf Coastal Plain,'" no. 10 phytochorion, Macrantha and Stachydeoma. They list 24 species as examples of local endemics. Perhaps the most important local area of endemism is along the lower Apalachicola River in western Florida and adjacent Georgia. This is the original location for Torreya taxifolia and Taxus floridana. Sorrie and Weakley (2001) referred to this phytochorion as the "Central panhandle of Florida." They noted that this Appalachicola River region "was an important refuge for plants during the Pleistocene and still harbors many relict populations of species ranging well to the north and west ... [and] harbors several Arcto-Tertiary relicts." They list 20 species, including those of Taxus and Torreya. Several species in the Asteraceae (Coreopsis grandiflora and Verbesina alterniflora) are narrow endemics to the Apalachicola region, and such endemism occurs in other families as well (in the Lythraceae, Cuphea aspera and Lythrum curtissii; and in the Lamiaceae, Scutellaria floridana and Stachys crenata). Harperocallis is an endemic genus of the Appalachicola River region (Wunderlin, 1998). Table 1, extracted from Wunderlin (1998), lists Florida endemics in the Apalachicola region and the remaining panhandle. In addition, James (1961) cites R. A. Howard as recognizing 39 endemic species in "northern peninsular Florida along the Georgia border." Ann F. Johnson (pers. comm., 2002) notes that "many endemics in [the] panhandle have a disjunct distribution or closely related species in [the] northern peninsula: Phoebanthus tenuifolius, Rudbeckia nitida (Asteraceae); Andropogon arctatus, Calamovilfa curtissii (Poaceae); and Nolina [atopocarpa] (Agavaceae)," Table II, also extracted from Wunderlin (1998), lists Florida endemics distributed in both the peninsular and the panhandle (mainly Apalachicola) regions.

B. THE CENTRAL FLORIDIAN SUBPROVINCE

Peninsular Florida, north of Dade and Monroe Counties and including the southern third of Georgia as well as extreme southern South Carolina and southeastern Alabama, is a large area of coastal plains endemism, both geographically and in richness. Table III lists Florida species endemic to this phytochorion. Sorrie and Weakley (2001) treat this region as "Southern South Carolina to peninsular Florida," no. 6. They estimate that 75 taxa fit this distribution, and they list 23 species or subspecies and two genera (Pinckneya and Serenoa).

Floristic endemism is concentrated especially in the endemic vegetation type called the "Florida Scrub." The following species and some genera are endemic or nearly endemic to the Scrub: Pinus clausa, Quercus inopina, Asimina tetramera, Ilex opaca var. arenicola, Persea humilis, Carya floridana, Prunus geniculata, Chionanthus pygmaeus, Osmanthus megacarpus, Ziziphus celata, Sabal etonia, Nolina brittoniana, Ceratiola ericoides, Asclepiadaceae (Asclepias curtissii, A. feayi), Lamiaceae (Calamintha ashei, Conradina brevifolia, C. grandiflora, Dicerandra christmanii, D. corniculata, D. cornutissima, D. frutescens, D. immaculata), Cistaceae (including Lechea cernua), Asteraceae (Liatris ohlingerae, Palafoxia feayii, Garberia heterophylla) and others (Christman & Judd, 1990; Myers, 1990; see also Harper, 1949).

James (1961) cites R. A. Howard as recognizing 189 species endemic to the Lake District of central Florida. Wunderlin (1998) lists the following taxa of the Annonaceae as endemic to central Florida: Asimina obovata, A. reticulata, A. tetramera, Deeringothamnus pulchella and D. rugelii (cf. Kral, 1960; Wilbur, 1970). Brown and Kirkman (1990) map the following woody plants as centered on peninsular Florida but ranging north only on the coastal fringes of the Gulf and Atlantic Coastal Plains: Tarodium ascendens [sic], Sabal palmetto, Myrica cerifera [sic], M. inodora [sic], Quereus chapmanii, Q. geminata, Q. hemisphaeriea, Q. myrtifolia, Q. virginiana, Lyonia ferruginea and Viburnum obovatum [sic]. Ann F. Johnson (pers. comm., 2002) noted that Taxodium aseendens, Myrica cerifera and Viburnum obovatum are widely spread throughout the Gulf coastal plain and that Myrica inodora is not present in peninsular Florida (cf. Wunderlin, 1998).

I believe that the large number ofendemics in the entire area, which includes central Florida and the Gulf and Atlantic coastal fringes, justifies the recognition of a Central Floridian Subprovince as a distinct unit of the Gulf and Atlantic Coastal Plain Province. D. I. Axelrod (1975) argued for the recognition of a floristic connection between some central Florida taxa and the Madrean flora. He proposed that the antecedents of scrub probably appeared during the early Tertiary as part of the sclerophyllous and microphyllous Madro-Tertiary Flora and spread from the southern Rocky Mountains and northern Mexico along the Gulf Coast to Florida (cf. Myers, 1990) and to the Greater Antilles and Central America (Borhidi, 1996). Pleistocene sea level did not rise higher than approximately 20 m above the present level, so that much of peninsular Florida was not inundated during maximum rise of sea level during the Pleistocene. Therefore, it is likely that Florida's "morphologically highly distinctive species, well isolated from their closest relatives" (James, 1961), are paleoendemics that represent a flora widespread during the Tertiary.

The monumental atlas of Florida flora (Wunderlin et al., 1996) permits us to examine the flora of this subprovince, county by county. In appendix 1 are listed, slightly modified stylistically, the 1479 taxa that constitute the flora of four counties of central Florida (Highlands, Polk, Okeechobee and Osceola) that fall wholly within this phytochorion. Appendix 2 lists the 1866 taxa that constitute the flora of four counties (Gadsden, Jackson, Holmes and Washington) that fall entirely within the SMHF (DEC) region of the coastal plains. Appendix 3 lists the 1671 taxa that constitute the flora of two counties (Dade and Monroe) that fall entirely within the Tropical Forest (TF) region of Florida. Despite the appearance in appendix 1--the four central Floridian counties--off a few northern Florida endemics, such as Taxus floridana and Torreya taxifolia (both clearly escapes from cultivation), that flora shares only 889 species (60%) with the one in appendix 2, the northern Florida set of four counties. Further supporting the separate floristic identity of central Florida, appendix 1 has only 824 species (56%) in common with the two tropical Florida counties (appendix 3). It is not surprising to note that only 481 taxa are shared among the three sets of data. This is additional evidence for the existence of a steep floristic gradient in Florida, north to south. These extensive appendix tables, derived directly from the CD--ROM "ISB Atlas of Florida Vascular Plants" by Wunderlin et al. (1996), are not included in the present article because of their length. They are available as Microsoft ExcelTM files from me (agreller2@optonline.net).

V. Review of Central Floridian Subprovince Vegetation: The Temperate Broad-Leaved Evergreen Forest Zone (Zonobiome V and Zonoeeotones V/II and V/VI)

A. GENERAL

Harper (1911, 1921) listed a number of arborescent vegetation types in central Florida. The following appear to be endemic or central to the Central Floridian Subprovince, which includes all of peninsular Florida north of Dade and Monroe Counties, the southern part of the panhandle west to Louisiana, extreme southeastern Georgia, and the outer Atlantic Coastal plain and islands, north to North Carolina: 1) Pinus elliottii var. elliottii Bays (with evergreen understory trees and shrubs); 2) Pond Cypress Domes (Taxodium ascendens ponds); 3) Bays (Persea borbonia, Gordonia lasianthus and Magnolia virginiana wet evergreen woodlands); 4) Scrub (Pinus clausa and evergreen shrubs on white, light yellow or light gray sand); 5) [Live Oak] Hammocks (Quercus virginiana); 6) Pine / Saw Palmetto Flatwoods (Pinus palustrisP elliotti var. densa-[P. elliotti var. elliottii]-P serotina / Serenoa repens); 7) Cutthroats (Pinus elliottii var. densa/Panicum [abscissum]); 8) Cabbage Palm Savannas and Woodlands (Sabal palmetto); 9) Low Hammocks (Hydric Hammocks); 10) Conifer (Pinus-Juniperus)-Cabbage Palm-Live Oak low woodland; and 11) Mixed Hammock forests (Quercus virginiana Liquidambar styraciflua-Carya glabra). Laessle (1942) defined hammocks as evergreen hardwood arborescent communities that occupy sites that are never permanently flooded. Harper (Vince et al., 1989) described hammocks as "dense hardwood forests that occur in limited areas amid the wet prairies, marshes, and pine forests of the coastal plain."

Laessle (1942) described the vegetation of the Welaka area of Putnam County, in northeastern Florida. Welaka occupies a position on the eastern shore of the St. John's River. It is wholly within the Central Floridian Subprovince. Laessle listed the following community types: Scrub and Sandhills ("Non-hammock communities of well-drained soils"), Hammock communities, Hydric communities dominated by trees, Flatwood communities on poorly drained soils, Herbaceous aquatic communities bordering the river and its tidal tributaries, Communities of flatwoods ponds and bogs, and Ruderal communities. Greller (1980) followed Braun (1950) in referring to this region as the Broad-Leaved Evergreen Forest Zone and considered it distinct from the mainly deciduous forest zones of central eastern North America.

Fujiwara and Box (1994) collected extensive original data on evergreen broad-leaved forests in the southeastern United States, both temperate and tropical. They included black-and-white photographs of the major forest types. In addition, they made some comparisons with similar types in East Asia (Fujiwara & Box 1994, 308).

B. CLASSIFICATION AND DESCRIPTION OF CENTRAL FLORIOIAN VEGETATION TYPES

1. Biogeocenes of Zonobiome V and Zonoecotones V/II and V/VI

a. Broad-Leaved Evergreen Forests

Broad-leaved evergreen forests (Hammocks of Laessle, 1942; Walter, 1985:18), dominated by evergreen trees, occur on a wide variety of soils but not on seasonally or periodically flooded sites:

* The Quercus virginiana Association (including Live Oak and Live Oak and Cabbage Palm Hammocks of Davis, 1943). This type, the "xeric hammock" of Laessle, is open and dominated by live oaks; subdominant trees are Quercus hemisphaerica (laurel oak), Sabal palmetto (cabbage palm), Quercus incana (bluejack oak), Pinus palustris (longleafpine) and Pinus taeda (loblolly pine). The epiphyte Tillandsia usneoides (Spanish moss) is abundant. Shrubs are also abundant: Quereus myrtifolia, Q. chapmanii, Vaceinium arboreum (sparkleberry), Rhus' copallina (dwarf sumac), Callicarpa americana (beantybush), [Vaceinium stamineum] (squawberry) and Lyoniaferruginea (staggerbush). Woody vines are Vitis rufotomentosa and g cordifolia (wild grapes), Vitis munsoniana (bullace grape) and Parthenocissus quinquefolia (Virginia creeper). Smilax auriculata (wild bamboo) is common. The herbaceous layer is sparse; grasses (Panicure, Aristida and Andropogon species), composites (Chrysopsis, Solidago) and legumes (Cassia, Desmodium) are the common families. At Welaka, Laessle reported Scrub plants: Ceratiola ericoides, Pinus clausa, Garberia [heterophylla] and llex ambigua. In the absence of fire, trees more typical of mesic and hydric hammocks occur as saplings: Persea borbonia (red bay), Magnolia grandfflora (bull bay), Magnolia virginiana (sweet bay), Prunus virginiana (choke cherry or black cherry) and Acer rubrum (red maple). Greller (1980) gave basal area data for a number of such stands throughout central Florida. Broad-leaved evergreens account for at least 70% of basal area; live oak is the first dominant, and Sabalpalmetto or Quercus hemisphaerica, the second. Other related stands are:

* Magnoliagrandiflora-Quercusvirginiana(Daubenmire, 1990). Daubenmire recognized a bull bay-live oak forest type for north central Florida. In northwestern Florida, Harper (1914) listed hammocks of the Gulf Hammock Region as being dominated by Quercus virginiana, Magnolia grandifiora, llex opaca, Quereus [hemisphaerica], and [Carya glabra]; and Greller (pers. observ.) noted live oak-bull bay forests in coastal Santa Rosa County, in the Florida panhandle.

b. Live Oak Dune Forests

The Live Oak (Maritime Hammock) Dune Forests of the Atlantic Coast (Bourdeau & Oosting, 1959) can be classified in the Live Oak Association. Stalter and Odum (1993) give dominance and importance value data for five stands of this type in South Carolina and Florida. Forests of this type also occur on the Sea Islands of Georgia and the Outer Banks of North Carolina. They are rare on the panhandle coast of Florida, being found there only on "shell middens, shelly ridges and some mainland sands" (Johnson & Barbour, 1990). Cabbage palms co-occur continuously with live oak to north coastal South Carolina. The northern limit of cabbage palm is on Smith Island, Cape Fear, North Carolina, where a live oak forest occurs. The leading dominants, according to Stalter and Odum (1993), are Quercus virginiana (live oak), Sabal palmetto, Quercus [hemisphaerica] and occasionally Pinus taeda. Other common trees are Persea [borbonia], Ilex opaca, Liquidambar, Magnolia grandiflora, Pinus elliottii and Juniperus silicicola, with Acer rubrum, Persea palustris and Ulmus sp. on a wetter site. Perhaps the northern stand of tall, well-grown live oak forest occurs as an outlier, on stabilized sand, in Virginia Beach, southeastern coastal Virginia (Greller & Ware, data collected on January 15, 1986). In that stand, live oak (Quercus virginiana) constitutes 53% of basal area; Ioblolly pine (Pinus taeda), 21.5%; laurel oak (Quercus hemisphaeriea), 16.0%; American holly (llex opaca), 8.6%. Other, deciduous taxa present are red mulberry (Morus rubra), wild black cherry (Prunus serotina) and sweetgum (Liquidambar styraciflua). Johnson and Muller (1993) reported that maritime hammocks in the extreme western panhandle are characterized by a canopy of sand live oak (Quercus geminata) and southern red cedar (Juniperus silicicola).

c. The Magnolia grandiflora--Ilex opaca Association

This is the "mesic hammock" of Laessle (1942). The vegetation is denser than in the xeric hammock; the soil is richer in organic matter and has a greater water-holding capacity; pH varies greatly from site to site depending upon the amount of calcareous material (shells) in the soil. At Welaka this association occurs on the slope between flatwoods and river swamp. Dominant trees are Magnolia grandiflora, Quercus hemisphaerica, Persea borbonia, Carya glabra, Ilex opaca, Quercus nigra, Prunus virginiana, Quercus virginiana, Liquidambar styraciflua. Occasional specimens of Pinus taeda, Tilia floridana (T. americana) and Sabal palmetto also occur. Shrubs and small trees occur here, including sparkleberry, saw palmetto, wild olive, beauty bush and Asimina parviflora (small-flowered pawpaw). Common vines are Gelsemium sempervirens (yellow jessamine), Vitis rotundifolia (scuppernong grape) Smilax bona-nox, Ampelopsis arborea. Parthenocissus quinquefolia (Virginia creeper) and Toxicodendron radicans (poison ivy). The sparse herbaceous vegetation includes the grasses Panicum joorii and P. equalaterale, Mitchella repens (partridge berry), Smilax pumila and Scleria triglomerata (a sedge).

d. The Sabal palmetto--Quercus laurifolia--Q, nigra--Q. virginiana--Liquidambar Association

This is the "hydric hammock" of Laessle (1942) and Vince et al. (1989). The canopy comprises mainly evergreen angiospermous trees. Canopy closure is 75-90%. Trees are usually 17-21 m tall. Dominants are cabbage palmetto, one or more species of evergreen oak and sweetgum. Less abundant are Florida elm, swamp tupelo, sweetbay, persimmon, green ash and red maple. Hornbeam often forms the lower tree layer. Trees are laced with woody vines such as trumpet creeper, pepper vine, poison ivy and wild grape. Epiphytic ferns and bromeliads occur on trunks and branches. Bluestem palmetto (Serenoa minor), greenbrier species or a mixture of saplings and shrubs occur in a sparse shrub layer. Various ferns, grasses, sedges and dicot herbs occur in a sparse ground layer.

Hydric hammock usually occurs where the water table is just below the surface and where rainfall and runoff from uplands are supplemented by seepage from springs. Soils are therefore subjected to a fluctuating hydrocycle, but flooding at the surface occurs only after heavy rains. At Welaka, these stands are present around seeps, where groundwater reaches the surface and the ground is perpetually wet. Vince et al. (1989) reported that hydric hammocks along the Myakka River can be deeply flooded for short periods. Soils are high in organic matter (peat); pH is variable. Fires are infrequent. Common trees present in this type are Sabal palmetto (cabbage palm), Quercus laurifolia (swamp laurel oak), Q. virginiana (live oak), Q. nigra (water oak), Liquidambar styraciflua (sweetgum), Carpinus caroliniana (hornbeam), Ulmus floridana (Florida elm; Ulmus americana of Wunderlin, 1998) and, occasionally, Pinus taeda (loblolly pine) and Juniperus silicicola (southern red cedar). Other trees reported as common are Acer rubrum (red maple), Magnolia virginiana (sweetbay), Nyssa sylvatica var. biflora (swamp tupelo) and Persea palustris (swamp bay). Common vines are Ampelopsis arborea (pepper vine), Berchemia scandens (rattan vine, supple jack), Campsis radicans (trumpet creeper), Decumaria barbara (climbing hydrangea), Smilax lourifolia (blaspheme vine), Toxicodendron radicans (poison ivy), Vitis aestivalis (summer grape) and V. rotundifolia (bullace grape). Prominent shrubs are Ilex spp., Myrica cerifera (wax myrtle), Cornus foemina. Baccharis halimifolia (groundsel tree; in open and disturbed areas), Callicarpa americana, Gelsemium sempervirens, Viburnum obovatum and Serenoa minor (bluestem palmetto). Herbaceous vegetation is sparse; common plants are Carex spp., Chasmanthium nitidum and C. laxum, Cyperus spp., Dryopteris ludoviciana, Elephantopus nudatus, Elytraria carolinensis, Oplismenus setarius, Panicum spp., Polygonum hydropiperoides, Thelypteris spp. and Viola affinis. Epiphytes are Epidendrum conopseum, Tillandsia recurvata, T. bartramia, T. setacea and T. usneoides (Vince et al., 1989). Some variations of the hydric hammock type follow.

* Genelle and Fleming (1978) described a "wet to mesic" hammock at Dunedin, Pinellas County, west of Tampa, in which the dominant trees were Celtis laevigata, Prunus serotina, Quercus virginiana, Carya glabra and Acer rubrum.

* Harper (1914) noted species-rich stands of "low hammocks" in the Gulf Hammock Region of northern Florida, west of the Suwanee River. He listed the following taxa: Pinus taeda, Sabal palmetto, Liquidambar, Quercus [laurifolia?], Carpinus caroliniana, Quercus nigra, Ulmus floridana, Persea [palustris], Morus rubra, Celtis [laevigata?] and Cercis canadensis.

* Vince et al. (1989) recorded a cabbage palm-southern red cedar (Juniperus silicicola)--live oak hydric hammock adjacent to salt marshes in the Gulf Hammock region at the Big Bend. This type also occurs adjacent to "freshwater prairie" along the upper St. Johns River.

* Vince et al. (1989: fig. 13) recognized a loblolly pine cabbage palm--swamp laurel oak--sweetgum hydric hammock in Florida's San Felasco Hammock State Preserve, Alachua County and Silver Springs Run, Marion County. At the latter site the dominants were (percentage of importance value) Pinus taeda (38), Sabal palmetto (26) and Liquidambar (17); subdominants were Quercus virginiana (7) and Q. nigra (7).

e. Quercus virginiana--Sabal palmetto--Tropical Hardwoods

The Quercus virginiana (live oak)-Sabal palmetto-tropical hardwoods of South Florida are a type of Florida ecotonal hammock (ZE V/II), in which live oak and cabbage palm are dominants but are accompanied in the canopy and the subcanopy by tropical hardwoods. For example, one "High Hammock Community" (Alexander & Crook, 1973, 1975) occurs just north of the Everglades Parkway in the eastern part of the Big Cypress Region. The dominant is live oak (up to 50 ft tall and 30 inches dbh). Persea borbonia (red bay, Lauraceae) reaches a height of 40 ft; cabbage palm is an understory tree up to 30 ft tall. Other Holarctic taxa present as small trees or shrubs are Morus sp. (Moraceae), Celtis laevigata (Ulmaceae) and Ilex cassine (Aquifoliaceae). Some tropical taxa in this forest are Myrcianthes fragrans (Myrtacaceae, up to 40 ft tall), Bursera simaruba (Burseraceae, up to 40 ft tall), Schoepfia schreberi (Olacaceae), [Ocotea] coriacea (Lauraceae) and Chrysophyllum oliviforme (Sapotaceae). Alexander and Crook give extensive floristic data for this type of hammock in South Florida. They occur mainly north of the Tamiami Trail and south of Lake Okeechobee in the west central part of the state. This type occurs in maritime hammocks all along the Atlantic Coast, from northern Palm Beach County north to Cape Canaveral. For example, in Palm Beach County the "low hammock" portion of Butts Hammock has the following dominants: Chrysophyllum oliviforme, Diospyros virginiana, Ficus aurea, Morus rubra, Pinus elliottii, Quercus virginiana, Sabal palmetto and Trema micrantha (Austin et al., 1977).

f. Evergreen Oak-Holarctic Deciduous Hardwoods

Evergreen oak-holarctic deciduous hardwoods (northern transition) are another type of ecotonal hammock (ZE V/VI), in which laurel oak (Quercus hemisphaerica) or live oak (Q. virginiana) and associated broad-leaved evergreen trees account for less than 50% of the basal area. It occurs in northern Florida and at the northern end and inland of the distribution of broad-leaved evergreen forests along the Atlantic Coast. Subdominant or codominant broadleaved evergreens in northern Florida are Magnolia grandiflora, Persea borbonia and Ilex opaca. Codominant deciduous trees are Carya glabra, C. tomentosa, Liquidambar styraciflua, Prunus serotina, Quercus alba, Q. austrina (a local dominant), Q. michauxii, Q. falcata, Tilia americana and Fagus grandifolia (Greller, 1980: table 1, stands 8, 10, 16, 17). Johnson and Barbour (1990) report "from Florida north to North Carolina [in live oak forest], percentage canopy cover by deciduous species increases as one moves inland or northward along the coast." Those authors list the following deciduous trees as frequent on South Carolina inner barrier islands and mainland peninsulas but rare on the outer barrier islands: in the canopy, Quercus falcata, Q. phellos and Liquidambar styraciflua; in the understory, Carpinus caroliniana and Cornus florida. The following combinations of dominants have been described in the literature or recorded by me:

* Quercus virginiana--Carya tomentosa--Liquidambar styraciflua (Crawfordville, FL.; Greller, 1980: table 1, no. 17).

* Quercus hemisphaerica--Pinus taeda/Carpinus caroliniana (Cape Hatteras, NC; Greller & Ware, unpubl, data, 1986). The northern limit of continuous evergreen oak forest may be Buxton Woods, at Cape Hatteras, where the dominants in one tract are laurel oak (58.8% of the basal area), Carpinus caroliniana (hornbeam or bluebeech, a deciduous understory tree; 14.3%), loblolly pine (13.0%) and Cornus florida (flowering dogwood, a deciduous understory tree; 10.9%). Also present are the evergreens Persea palustris, live oak, and Ilex vomitoria; Sabal minor is a common understory shrub. Similar but isolated stands dominated by Quercus hemisphaerica occur in Nags Head Woods, north of Cape Hatteras (Greller & Ware, unpubl, data) and in the "closed interior forests near the coast" (Stalter & Odum, 1993).

* Pinus taeda/Carya glabra-Quercus hemisphaerica (Duck, NC; Greller & Ware, unpubl. data, 1986; cf. Ware et al., 1993: table 3, no. 9). This is a recently disturbed stand in which young laurel oak populations are reaching the canopy and growing rapidly, while large hickories show little reproduction.

2. Biogeocenes of Pedobiome V and Pedoecotones V/II and V/VI

a. Scrub

Scrub (a peinobiogeocene) is a two-layered community of sand pine (Pinus clausa), with an understory of evergreen shrubs that reach 6-8 ft (2.5 m) tall. Epiphytes of Spanish moss (Tillandsia usneoides), true mosses, lichens and liverworts are plentiful. Infrequent crown fires periodically reduce the shrub height. All shrubs sprout from the root crown, except for the oaks, which are rhizomatous, and for Ceratiola ericoides, which does not resprout but sets seed (Ann F. Johnson, pers. comm., 2002). Herbaceous vegetation is sparse. Patches of white or gray sand are frequent. Small, heavily cutinized, revolute and hairy leaves characterize scrub vegetation. In open sites the first few inches of soil are dry, but at 6 inches of depth the soil is nearly always found to be moist. Plants often grow so densely that the ground is moist directly beneath them. The soil is poor in nutrients, especially potassium, being coarse and retaining little organic matter. Scrub is characterized by a low, woody vegetation of shrubs that usually comprises the following dominants: Quercus myrtifolia (myrtle oak), Quercus inopina (scrub oak), Serenoa repens (saw palmetto), Quercus geminata (sand live oak), Quercus chapmanii (Chapman's oak), Lyonia ferruginea (rusty lyonia) and Ceratiola ericoides (Florida rosemary; Myers, 1990).

Pocket gophers (Geomys pinetis) and gopher tortoises (Gopherus polyphemus) are reported to be found in this community, although Ann F. Johnson (pers. comm., 2002) claims that the gophers are typical of sandhill communities. The Florida scrub jay (Aphelocoma coerulescens coerulescens) is endemic to this vegetation type. Other endemic vertebrates are the Florida mouse (Podomys floridanus), the Florida scrub lizard (Sceloporus woodi), the sand skink (Neoseps reynoldsi) and the blue-tailed mole skink (Eumeces egregius lividus). In Florida, Scrub extends from the area immediately north and east of Lake Okeechobee north to a line connecting the Etoniah Creek area in Putnam County, north central Florida, with St. Vincent's Island, Franklin County, on the Gulf Coast. Scrub is continuous along the Florida panhandle coast west at least to Ono Island, Alabama (Ann F. Johnson, pers. comm., 2002). Scrub outliers extend to southern Georgia (e.g., Big Hammock Natural Area, Tattnall County) and Alabama. A notable stand of scrub, The Big Scrub, occurs in Marion County, Florida. Endemic species comprise 40-60% of the flora. Most rare endemic taxa of the Scrub, such as Chionanthus pygmaeus (pygmy fringe tree), Prunus geniculata (scrub plum) and Ziziphus celata (Garrett's ziziphus), are restricted to the Lake Wales Ridge and centered on Polk and Highlands Counties (Myers, 1990).

* The St. Lucie Scrub (Pinus clausa/Quercus spp. Association). In this association the open canopy of sand pines (40 years old, 86 stems/acre, 34.2 cm mean dbh; Myers, 1990) has an evergreen shrub layer beneath it. Dominant shrubs include Quercus geminata (twin live oak), Q. chapmanii (Chapman's oak), Q. myrtifolia (myrtle oak), Lyonia lucida (fetterbush), Vaccinium myrsinites (blueberry), Lyonia ferruginea (staggerbush) and Serenoa repens (saw palmetto). Other shrubs are Sabal etonia (scrub palmetto), Ilex opaca var. arenicola (scrub holly), Ilex ambigua, Persea humilis (silk bay), Osmanthus megacarpa (wild olive) and Garberia heterophylla. Rare plants here are Ceratiola ericoides (Florida rosemary), Opuntia austrina (semaphore cactus), Selaginella arenicola and Licania michauxii (gopher apple). Nevertheless, Ann F. Johnson (pers. comm., 2002) reports that all of the rare plants are common in Florida rosemary scrubs. Epiphytes are Tillandsia usneoides (Spanish moss), true mosses, lichens and liverworts. Vines are Smilax auriculata (wild bamboo) and Galactia elliottii (Elliott's milk pea). The two common herbs are the graminoids Rhynchospora megalopcarpa (beak rush) and Panicum potentifolium. Mats of mosses and lichens (Cladonia leporina, C. prostrata, Cladina evansii and C. subtenuis) occur at ground level (Laessle, 1942; Myers, 1990).

* Scrubby Flatwoods. Although Scrubby Flatwoods is listed as a single vegetation type by Laessle (1942) and Myers (1990), Ann F. Johnson (pets. comm., 2002) reports that it refers to two different types. The first is a dense growth of shrubs, lacking sand pines. Dominant shrubs are those listed above but without Osmanthus, Ilex opaca var. arenicola and Persea. The second type comprises scattered oaks and shrubs that are more typical of flatwoods, such as Ilex glabra and Lyonia lucida. Aristida stricta (wire grass) is common here and occurs in scattered patches between shrub clumps. In the Florida panhandle these are referred to as "coastal scrub communities." Pinus elliottii van elliottii (slash pine, forming "slash pine scrubs") is occasionally present (see "Slash Pine Flatwoods," below). Only the first type is considered classifiable as "Scrub."

* Sand Pine / Rosemary Scrub. This scrub occurs on white sand at the southern end of the Lake Wales Ridge in Hendrie Ranch, Highlands County and on recent coastal dunes in the panhandle, from Dog Island west to Alabama. This is a stand of uneven-aged sand pines with a maximum age of 100 years. There are 67 trees per acre, with a mean diameter of 24.1 cm for trees older than 40 years. The shrub layer is dominated by Ceratiola ericodes and Quercus inopina (scrub oak) and is low and open.

* Sand Pine Forest (Pinus clausa; a peinobiogeocene). This forest is recognized in this study as a distinct type of vegetation because the pines can form a closed canopy where evergreen shrubs are few and scattered in the understory. Nevertheless, there is a continuum of vegetation from the treeless scrubby flatwoods to the sand pine forest, both spatial and temporal. The forest provides habitat for a number of arboreal mammals and for birds that are absent in scrubby flatwoods. Two populations of sand pine occur, one in the peninsula and the other in the panhandle and in southern Alabama. They are separated at their nearest point by 200 km. The two areas are represented by two varieties: Pinus clausa van clausa, the peninsular variety; and P clausa var. immuginata (Choctawhatchee sand pine), the panhandle variety. The latter variety is generally nonserotinous. These pines grow on well-drained, sandy ridges and gentle hills that burn infrequently. Sand pine is considered "fire resilient," because of its ability to regenerate rapidly from seed after fire. Serotinous and nonserotinous individuals compose the population in even or uneven-aged stands. Trees as young as 5 years old can produce cones, and individuals rarely reach 100 years. On the best sites, the trees can reach a height of 20 m and a maximum diameter of 45-50 cm. The largest tree grows in Orange County, north of Orlando, and is 26 m tall, has a diameter of 61 cm and has a crown spread of 12 m. Seedlings are reported to be shade tolerant but show poor regeneration "in the shade of mature sand pine scrub vegetation." Sand pine invades "high pineland" (sandhill) of Pinus palustris with an understory of deciduous oaks (Quercus laevis, Q. incana, Q. spp.; Myers, 1990).

b. The Pinus elliottii var. elliottii Association

These Slash Pine Flatwoods (Laessle, 1942) are characterized by a relatively "open overstory of pines, an extensive low shrub stratum, a variable and often sparse herbaceous layer ... [and a] xerophytic and pyrophytic physiognomy" (Abrahamson & Harnett, 1990). In central Florida this type (a psammobiogeocene or lithobiogeocene on limestone) occurs in low, poorly drained soils. At Welaka it is confined to marginal sites between wetlands and Longleaf Pine Flatwoods; Pinus serotina and Pinus palustris are occasionally present here with Pinus elliottii. A number of understory types are present: near the bayheads are shrubs such as saw palmetto, gallberry, wax myrtle, blackberry (Rubus betulifolius), chokeberry (Aronia arbutifolia) and Berchemia scandens; nearer the longleaf pine uplands are herbaceous understories of Andropogon spp.

c. Mixed Pine Woodlands

In Mixed Pine Woodlands (a psammobiogeocene), canopy trees include Pinus palustris, P. elliottii and Quercus geminata. Understory trees include Quercus laevis, Q. incana, Q. falcata and Diospyros. Licania michauxii (gopher apple, Chrysobalanaceae) is a common shrub. Aristida stricta and Sporobolus junceus (dropseed) are the common herbs (Christenson, 1988). Genelle and Fleming (1978) list an Oak-Pineland on sandy loam at Dunedin, near Tampa, in Pinellas County, Florida. Dominant trees are Pinus elliottii, Juniperus silicicola, Quercus [hemisphaerica] and Quercus virginiana. Understory shrubs are Prunus caroliniana, Psychotria nervosa and Myrica cerifera. Brown (1976: fig. 2) shows a "pine-palm savanna" in the "coastal plain of Charlotte County, southwest peninsular Florida." This may be the "Scrubby Flatwoods" (occasional fires) or "Mesic Flatwoods" (frequent fires) of the Florida Natural Areas Inventory (1998). Mixed Pine Woodlands appear to be transitional from the Xeric Hammock to various pine woodlands "or transitional from 'sandhill' of [longleaf pine,] wiregrass and turkey oak to hardwood forest" (Ann F. Johnson, pers. comm., 2002).

d. South Florida Slash Pine Flatwoods

The South Florida Slash Pine (Pinus elliottii var. densa) Flatwoods (Pine Rockland; lithobiogeocene and psammobiogeocene) occurs throughout central and southern Florida, south of Lee, Desoto, Highlands and Okeechobee Counties. In Broward County, it occurs on "moderately to well-drained sandy soils," but farther south (Dade County) it is found on "outcrops and low ridges of oolitic limestone" (Abrahamson & Harnett, 1990). Two variants of this community can be recognized by understory composition. These are:

* South Florida Slash Pine / Live Oak, which occurs in the southwest, "where limestone is mantled by sand, dwarfed live oak and myrtle oak are abundant and herbs are evenly distributed" (Abrahamson & Harnett, 1990). This could be classified in PB V.

* South Florida Slash Pine / Palms type, which occurs in the southeast and the Florida Keys, where oolitic limestone forms the surface. The palms are Coccothrinax argentata. Thrinax morrisii, T. radiata and Sabal palmetto. Understory trees include "running oak" in the southeast and Metopium toxiferum and Drypetes diversifolia in the Keys. Among the shrubs present are Serenoa repens, Manilkara bahamensis, Mysine floridana and Zamia floridana (Abrahamson & Harnett, 1990; Greller, pers. observ., 1994). This could be classified in PE V/II.

e. Mixed "Bay" Forests

Mixed "Bay" Forests ("Bayheads," "Baygalls," "Carolina Bays"; a helobiogeocene) occur on peaty, very acidic, saturated soils that are subject to periodic flooding in central Florida and near the Atlantic Coast. Magnolia virginiana (sweet bay; common on the wettest sites), Persea palustris (swamp bay; common on the driest sites), Gordonia lasianthus (loblolly bay; common on the intermediate sites) and Nyssa sylvatica var. biflora form dense, tall swamp forests; occasional pines emerge through the canopy. Bay forests are dominated by broad-leaved evergreens in central Florida. They show increasing dominance by deciduous hardwoods northward to North Carolina and westward to east Texas. Important shrubs are Cyrilla racemiflora, Lyonia lucida, Ilex coriacea, Myrica heterophylla, Vaccinium corymbosum and Zenobia puberulenta (in South Carolina). Smilax laurifolia is an important vine; Woodwardia virginica is a common herb (Laessle, 1942, Christenson, 1988). This type could be classified in PB V.

f. The Sabal palmetto Association

The Sabal palmetto Association (an amphibibiogeocene) was described for South Florida by Davis (1943; Cabbage Palm Hammocks). Cabbage palm savannas occur along the Atlantic Coast south of St. Augustine (pers. obs.), in the Big Bend area of Gulf Coastal Florida (Lee to Franklin Counties), on the Indian Prairie northwest of Lake Okeechobee, on Merritt Island, and in the upper St. John's River basin, east of Orlando (Abrahamson & Harnett, 1990; Ann F. Johnson, pers. comm., 2002). They are pure, apparently even-aged, stands of cabbage palms that occupy alternately wet and dry, undrained depressions. Vince et al. (1989) treats pure stands of cabbage palm as an extreme type of hydric hammock. This type could be classified in PB V.

g. The Pinus serotina / Lyonia lucida Association

The Pinus serotina / Lyonia lucida Association (Black Pine and Fetterbush Flatwoods of Laessle, 1942; an amphibibiogeocene), a two-layered community, occurs in low, periodically wet sites in longleaf pine stands. On the soil surface there is an organic layer that is half an inch thick. It is hard (hardpan) and acidic. Pinus serotina is scattered, and Lyonia lucida often forms extensive, nearly pure shrublands. Pinus elliottii and Pinus palustris are also present. Other shrubs are dwarfed Serenoa repens, Ilex gabra, Gaylussacia dumosa, [Lyonia] fruticosa and Vaccinium myrsinites. Herbaceous vegetation is sparse and represented by Andropogon spp. (broom sedges) and Aristida spiciformis, both grasses. This type could be classified in PB V.

h. Pond Cypress "Domes"

Pond Cypress "domes" (helobiogeocene) occur in poorly drained depressions throughout the southeastern coastal plain. They are small, forested wetlands dominated by Taxodium ascendens (pond cypress). Water level is deeper than in bay forests, the pH is 4.1-4.6, and soil is nutrient poor, especially in phosphorus. Tillandsia usneoides is a ubiquitous epiphyte. Associated trees and shrubs are Ilex cassine, Nyssa sylvatica var. biflora, Cyrilla racemiflora, Magnolia virginiana, Lyonia lucida, Persea borbonia, Clethra alnifolia and Vaccinium spp. Pond Cypress communities differ ecologically from Bald Cypress, which occurs on phosphorus-rich substrates, in moving water. Pond Cypress stands are best developed in central and southern Florida, where nearly pure stands occur draped with many species of Tillandsia. This type could be classified in PB V.

i. Maritime Shrub and Scrub Forest Communities

Maritime Shrub and Scrub Forest Communities, a series of psammobiogeocenes on dunes and strand, are types that can be classified as PB V.

* Ilex vomitoria--Myrica cerifera Dune Shrubland occurs on windward dunes as an impenetrable thicket. Associated taxa are Baccharis (3 spp.), Rhus copallina, Smilax auriculata, Amelopsis arborea, Berchemia scandens, Parthenocissus quinquefolia, [Toxicodendron] radicans, Smilax spp. and Vitis rotundifolia (Stalter & Odum, 1993). Myrica cerifera (wax myrtle) dominates a "scrub" on Amelia Island, Florida, associated with Baccharis halimifolia, Ilex vomitoria, Sabal palmetto and Juniperus silicicola (Johnson & Barbour, 1990).

* Saw Palmetto Scrub, 1.5 m tall, occurs in dune lee slopes and flats, on Vilano Beach, St. Johns County, Florida. Serenoa repens is the dominant of this community, one that includes Bumelia tenax, Ilex vomitoria, Myrica cerifera and Vaccinium arboreum. Sabal palmetto is an occasional emergent (Johnson & Barbour, 1990).

* Tall Mixed Dune Shrubland occurs on older dunes and appears to be successional from the Ilex-Myrica type. Here the matrix of Ilex vomitoria and Myrica cerifera, with Serenoa repens, forms a lower layer for tree taxa such as Juniperus silicicola, Persea palustris, Quercus virginiana and Sabal palmetto. In 1974, Au (in Johnson & Barbour, 1990) reported a "Myrica-Juniperus flat" on Shackleford Banks, North Carolina.

* Quercus virginiana (Live Oak)-Bumelia tenax (Buckthorn) Shrubland was reported by Hillestad (cf. Stalter & Odum, 1993) for Cumberland Island, Georgia. This type occupies the tops and rear slopes of rear dunes. In the canopy, in addition to the dominants, are Persea palustris, Pinus elliottii and P. taeda. Shrubs, vines and juvenile trees include Quercus virginiana, Serenoa repens, Bumelia tenax. Zanthoxylum clava-hereulis, Myrica cerifera, Ilex vomitoria, Lyonia ferruginea, Vitis rotundifolia, Smilax laurifolia and Ampelopsis arborea. Herb cover is sparse.

* Pinus serotina--Pinus elliottii (Pine)--Quercus virginiana (Live Oak) Scrub Forest occurs on cutover, moderately poorly drained soils on Cumberland Island, Georgia (Hillestad, in Stalter & Odum, 1993). The pines and oaks are associated with understory trees and shrubs such as Persea palustris, Lyonia lucida. L. ferruginea, Gaylussacia frondosa, Bejaria racemosa and Ilex glabra. Some herbs are Galactia. Pteridium, Scleria and Andropogon.

* Quercus (Live Oak) Scrub Forest occurs on moderately drained soils from which timber has been removed, on Cumberland Island, Georgia (Hillestad, in Stalter & Odum, 1993). It is a community of dense, scrubby broad-leaved evergreens and scattered pines. It is reported as successional to Live Oak / Saw Palmetto Forest. Canopy trees are Quercus myrtifolia, Q. virginiana, Q. chapmanii, Pinus elliottii, P serotina (rare), P palustris (rare) and Persea palustris. Some shrubs, vines and juvenile trees are Serenoa repens, Myrica pennsylvanica, Lyonia ferruginea, Quercus myrtfolia, Ilex glabra, Gaylussacia frondosa and Vaccinium myrsinites. In northeastern Florida, Quercus myrtifolia scrub includes Juniperus silicicola, Sabal palmetto, Bumelia tenax, Persea borbonia and Magnolia grandiflora (Johnson & Barbour, 1990).

* Live oak scrub (Johnson and Barbour 1990) "is dominated by two scrub oak species, sand live oak (Quercus geminata) and myrtle oak (Q. myrtifolia), which are present in almost all stands of this community throughout all the coastal regions in which it occurs."

* Sand live oak (Quercus geminata) / Q. myrtifolia-Serenoa repens) Dune Woodland is the "xeric hammock" of Johnson and Muller (1993). "It appears to develop from oak scrub as sand live oak, released from suppression by salt spray as one goes inland from the coast, grows up to the size of a small tree and forms a canopy over the other shrubs. This fairly uniform community is most extensive on Cape Canaveral and the western portion of Santa Rosa Island."

* A "Rosemary Zone" occurs on more recently stabilized dunes, on St. Vincent Island and other barrier islands (Dog Island, St. George Island, Santa Rosa Island and Perdido Key) off the northern Gulf Coast of Florida (Ann F. Johnson, pers. comm., 2002). Here, Rosemary (Ceratiola ericoides) is accompanied by a variety of herbs, including Chrysoma pauciflosculosa, Sehizachyrium maritimum, Uniola paniculata, Dicanthelium sp., Opuntia pusilla, Oenothera humifusa, Physalis angustifolia, Helianthemum arenicola and Cnidoscolus stimulosus, as well as the lichen Cladonia leporina (Johnson & Barbour, 1990).

* Rosemary Scrub occurs also on St. Vincent Island, on long-stabilized dunes. Rosemary (Ceratiola ericoides) predominates on dune crests, while oaks occur on dune slopes. Associated with Ceratiola ericoides are Quercus geminata, Q. myrtifolia, Conradina canescens, Chrysoma panciflosculosa, Serenoa repens, Smilax auriculata, Lyoniaferruginea and Vaccinium arboreum, along with the lichens Cladonia evansii and C. leporina (Johnson & Barbour, 1990).

C. RELATED VEGETATION IN THE GULF REGION OF LOUISIANA AND TEXAS

1. Cheniers

Natural ridges (up to 3 m asl) on the Chenier Plain of coastal Louisiana and Texas, oriented east-west parallel to the Gulf of Mexico, are referred to as "Cheniers" when they are covered with live oak forest. Gosselink et al. (1979) described the vegetation on such natural and artificial ridges. They listed the following trees as characteristic of the Louisiana cheniers: live oak, hackberry, American elm, Drummond red maple, bald cypress, water locust, prickly ash, persimmon, and water oak; palmetto is listed as one of the understory plants. Upland vegetation at the northern edge of the Chenier Plain is listed as loblolly pine--shortleaf pine type; the hardwood associates of this forest are mainly deciduous. Neyland and Meyer (1997) listed 19 species at 6 Chenier sites in southwestern Louisiana; the following taxa were the dominants (percentage cover): Quercus virginiana (61.8), Celtis laevigata (13.1), Ulmus americana (6.5) and Sapium sebiferum (Euphorbiaceae, exotic; 6.5). Penfound and Howard (1940) gave quantitative data for a live oak forest near New Orleans. The paucity of evergreen tree taxa in this forest suggests affinities with Evergreen Oak-Holarctic Deciduous Hardwoods (TBEF/SMHF, the northern transition), as outlined above. Grace et al. (2000) describe ecological conditions associated with a "coastal tall-grass prairie" in this region of Louisiana (Vermilion Parish).

2. The Texas Gulf Coastal Prairie

The Texas Gulf Coast, southwest of the Pine Woods of East Texas and south to the Mexican border, is mapped as the "Gulf Prairies and Marshes" region (Simpson, 1988). In the Texas Parks and Wildlife (1984) map, the coastal prairie region extends from Jefferson County, on the northeastern coast, south to Aransas County. Most of the intervening region is mapped as cropland. Pecan-Elm (Carya illinoensis-Ulmus) is the common riverine forest throughout this region. South of this section of the Gulf Coast, in Aransas County and farther south throughout Brooks and Kenedy Counties, vegetation is mapped as Live Oak Woods / Parks (Quercus virginiana, sic). Twenty miles (32.2 kin) inland from the Aransas Live Oak Woods is a small area mapped as "Prosopis glandulosa-Quercus virginiana [sic]-Condalia hookeri Parks" (Texas Parks and Wildlife, 1984).

Perhaps the best documented forests of this phytogeographical region are in the northern Texas coastal prairie, where a number of other woodland types have been described, mainly comprising deciduous hardwoods and broad-leaved evergreens. For example, woodlands of coastal live oak--post oak (Quercus virginiana--Q, stellata) and coastal live oak--pecan (Q. virginiana--Carya illinoensis) have been recognized on clay pan soils. Water oak--coastal live oak (Q. nigra--Q. virginiana) woodlands have been described for floodplains; and coastal live oak--sugarberry (Q. virginiana--Celtis laevigata) woodlands have been described near the coast. Other taxa associated with these woodlands are Fraxinus spp., Ilex vomitoria, Persea borbonia, Quercus laurifolia / Q. hemisphaerica and Ulmus crassifolia (Gosselink et al., 1979). These forests appear to be physiognomically related to the Mixed Hammock type of central Florida and to communities of the northern transition (TBEF/SMHF).

In considering the climatic nature of the Chenier and Texas Gulf Coastal Prairie regions, it is helpful to refer to the climate of the TBEF in Florida. Figure 6 in Greller (1980) shows isotherms of mean daily minimum temperatures of the coldest month (January). The isotherm of 5.5[degrees]C (41.9[degrees]F) approaches congruence with the TBEF/SMHF (ZE V/VI) northern limit line (of. Greller, 1980: fig. 2). Greller (1980: table 3) shows that the TBEF of Florida exists under a range of mean annual precipitation (MAP), from 163.1 cm (64.2 in) in Pensacola, to 120.1 cm (47.3 in) in Fernandina Beach, to 133.5 cm (52.6 in) in Punta Gorda.

Referring to the Texas MAP isoclines (Larkin & Bomar, 1983:18), one can see that only the extreme eastern portion of Texas, on and just north of the Gulf of Mexico, shows isoclines above 48 inches. Thus, the Chenier region of Louisiana and adjacent coastal Texas has sufficient MAP to support climatic broad-leaved evergreen forest (TBEF). The Texas January average minimum temperature isotherm of 42[degrees]F (Larkin & Bomar, 1983: 22) passes through the Chenier region, further supporting the existence of climatic TBEF vegetation there (TBEF/ SMHF; ZE V/VI). The restriction of live oak--deciduous hardwood forest to isolated ridges (cheniers) within coastal grassland may well be due to regional high-water tables that encourage the development of wet prairies. Thus, chenier/wet prairie may be classified as a hydrobiome of PE V/VI.

Conversely, MAP in the Texas Coastal Prairie region (Figure 1), ranges from 48 inches in the north Gulf Coast, to only 26 inches near Brownsville, in the extreme south (Larkin & Bomar, 1983:18). Thus, we can conclude that the "Warm-temperate, Humid" life zone (ZB V; TBEF) is excluded by low annual precipitation from Texas south of the Chenier region. Nevertheless, average January minimum temperatures are high enough (42[degrees]F) all along the Texas Gulf Coast, and increasing inland to the south (Larkin & Bomar, 1983: 22), to account for the existence of live oak woodlands under suitable edaphic conditions (i.e., locally high water table or on deep, moisture-retaining soil). We may tentatively conclude that Texas Coastal Prairie / Live Oak Woods represents a zonoecotone between prairie and live oak forest (ZE VII/ V, with ZE VII/V/II perhaps in the extreme south of the Gulf Coast).

D. RELATED FLORA AND VEGETATION IN THE GREATER ANTILLES

In the Greater Antilles and around the Caribbean Sea, a number of communities codominated by Holarctic, Madro-Tethyan (cf. Borhidi, 1996) genera occur, mainly in the mountains. Although all of these communities most likely deserve to be treated in a separate floristic province of southeastern North America, it is convenient to mention them in this discussion. Most lowland vegetation of this region is treated in the Neotropical Kingdom: Central American Region: West Indian (Antillean) Province.

1. Cuba and Jamaica

Borhidi (1996) lists the following taxa as representative of the "Madrean-Tethyan" geoflora that penetrated into Cuba, presumably during the Lower and Middle Miocene: Pinus, Juniperus, Quercus, Juglans, Buxus [sic], Ilex, Lyonia, Vaecinium, Pieris, Kalmiella [sic], Berberis, Celtis, Prunus, Myrica, Zizyphus, Euphorbia, Forestiera, Sabal, Poepalanthus, Lachnocaulon, Syngonanthus, Eriocaulon, Chaetolepis, Bejaria and Garrya. Many of the taxa listed by Borhidi appear to be tropical taxa rather than Madrean-Tethyan; e.g., Acacia, Calliandra, Erythrina, Karwinskia, Reynosia, Colubrina, Thouinia, Dodonaea, Myrtus, Psidium, Amyris, Helietta, Auerodendron, Sarcomphalus, Rhacoma, Coccothrinax and Maytenus.

In addition, Borhidi (1996) described in detail a number of plant communities, or strata of those communities, that are dominated or codominated by Holarctic genera or families. Among these taxa are Pinus, Quercus, Magnolia, Lauraceae, Theaceae, Cyrillaceae, Araliaceae, Ericaceae and Cistaceae.

a. Live Oaks--Tropical Hardwoods--Pines

Related to the Florida category of ecotonal live oak--tropical hardwoods we can consider the live oak, live oak--Microcycas, and live oak--pine, and perhaps the Pinus caribaea flatwoods of the northern Bahamas and Pinus tropicalis forests of Cuba.

* Quercus oleoides ssp. sagraeana Forest. In the lowlands and middle elevations of Pinar del Rio Province, in western Cuba, is a sclerophyllous evergreen oak woodland (30% tree cover, 10-12 m tall) on sandstone or white sand. There is an understory layer of shrubs (85% cover, 1-6 m tall) of mainly tropical affinities, including Miconia and Coecothrinax, among many others. There is also an herb layer, less than 1.5 m tall, with 60% cover, of grasses, sedges, tropical shrub taxa and herbs (Borbidi, 1996). For this oak forest, on acidic sandstone in the Sierra de los Organos, Lotschert (1974: 272) gives an extensive list of species. Among the characteristic plants he lists are Quercus virginiana [Q. oleoides ssp. sagraeana of Borhidi, 1996], Clusia rosea, C. minor, Hypericum styphelioides, Chiococca alba, Davilla rugosa and Miconia serrulata. Microcycas calocoma and Tillandsia flexuosa are the only two Cuban endemics listed for the community, which is otherwise characterized by tropical shrub taxa, ferns and bromeliad epiphytes. These evergreen sclerophyllous oak communities also occur on flatlands associated with limestone mogotes (steep-sided monoliths) in Pinar del Rio. Howard (1973) describes Quercus and Microcycas woodlands, with shrubs of Bejaria, Kalmia, Pieris (Ericaceae), Lechea (Cistaceae) and Lachnocaulon (Eriocaulaceae).

* Oak-Caribbean Pine Forest. Oak-pine mixed forests and pine forests occur on the "slatey sandstone" of the Sierra de los Organos and Sierra del Rosario of Pinar del Rio Province, Cuba. Borhidi (1996) lists the following characteristics of those oak-pine forests. The high tree layer has 40% cover and is 15-18 m tall. Pinus caribaea and Quercus oleoides ssp. sagraeana dominate it. There is a lower tree layer with 60-70% cover, 610 m tall, which includes, in addition to the oak, Acoelorrhaphe and Coccothrinax (palms); Calophyllum, Clusia, Didymopanax, Guarea, Matayba and Xylopia. A shrub layer 2-4 m tall, with 50-60% cover, contains, in addition to a number of tree taxa listed above, Alsophila, Amaioua, Dendropanax, Miconia, Rhus copallina vat. leucantha, Psidium, Tetrazygia and Vaccinium ramonii. There is an herb layer, up to 1 m tall, with 70% cover, of shrubs (including Zamia silicea), herbs, grasses and ferns. Lianas and epiphyte life forms are poorly developed.

b. Tropical Pine Forests

Tropical Pine (Pinus tropicalis) Forests occur on sand on the Isla de la Juventud (formerly Isla de Pinos) and in Pinar del Rio, Cuba. The canopy of Pinus tropicalis has 10-30% cover; the shrub layer, 10-30% cover. It includes the palms Acoelorrhaphe and Colpothrinax; also Byrsonima, Chaetolepis, Kalmia ericoides, Lyonia myrtilloides and Tabebouia. There is an herb layer of 40-100% cover, which includes grasses and Xyris.

c. Montane and Upper Montane Forests and Shrublands

* Magnolia-Ocotea Wet Montane Rainforests (Fangales) occur at 800-1600 m, in the Sierra Maestra, Sierra Escambray and Sierra del Purial, Cuba. In the upper canopy are Magnolia cubensis, Ocotea (3 spp.), Myrsine coriacea, Cyrilla racemiflora; in the lower canopy, Clusia taterastigma, Gomidesia lindeniana, Alchornea latifolia, Garrya fadyenii, Miconia punctata, Ossaea ottoschmidtii. Three species of the tree fern Cyathea are in the upper canopy. The epiphytes Orchidaceae and Bromeliaceae are in the upper canopy, and ferns, mosses and liverworts in the lower canopy. The ground layer comprises terrestrial orchids and shade-tolerant lianas. A Magnolia-Cyrilla montane rain forest occurs in the Escambray Mountains. Prestoa montana (Arecaceae) dominates the secondary forests at 800-1200 m (Borhidi, 1996).

* The Podocarpus urbanii--Cyrilla racemiflora--Alehornea latifolia Montane Mist Forest of Jamaica (Asprey & Robbins, 1953) is a low-canopied (40-50 ft tall), wet and misty forest in the Blue Mountains, at 4500 ft to more then 7000 ft (1372 m to 2134 m). Trees are tall and spindly, with branching, bushy crowns. Other trees are Clethra occidentalis, Brunellia conocladifoliua Solanum punctatum, Laplacea haematoxylon and Ficus harrisii.

* Weinmannia pinnata--Cyrilla racemiflora Cloud Forests are found at 1600-1900 m on Pico Turquino and Pico Payamesa. The climate is cool, equable and with heavy precipitation (280-320 cm/yr). The canopy is closed, very dense and 6-12 m tall. Twisted, gnarled trees with small, sclerophyllous and pachyphyllous leaves dominate the canopy. Tree ferns of many species are common. The shrub layer is dense and contains abundant pteridophytic vines. Orchid and fern epiphytes are also abundant. Mosses and liverworts cover the ground, branches and leaves. In addition to Weinmannia pinnata and Cyrilla racemiflora, some of the other canopy trees are in the following genera: Myrsine, Nectandra, Sapium, Persea, Symplocos and Garrya; the tree ferns are Cythaea, Alsophila and Lophosoria.

* Ilex-Laplacea (Gordonia) Semi-Arid Montane Serpentine Shrubwoods (the Charrascales of Cuba) is considered by Borhidi (1996) as an edaphic climax in a rainforest climate, at 600-1000 m. It is a dense shrubland (4-6 m tall), with some emergent trees (7-10 m) and with sclerophyllous, microphyllous and nanophyllous leaves. The dominant taxa are Ilex with four species, Laplacea (Gordonia) with two, and Clusia with 3. Other common taxa are Rauwolfia, Byrsonima, Lyonia spp., Cyrilla cubensis, Tapura, Myrica, Alsophila, Jacaranda, Illicium, Xylosma, Coccoloba, Garcina, Annona, many endemic taxa, a few epiphytes, numerous sclerophyllous lianas and some herbs. Variants of this type are dominated by species of Clusia. Myrica-Baccharis and Myrica-Lyonia communities are closely related shrublands that occur on Central American volcanoes and in the Blue Mountains of Jamaica, respectively (Borhidi, 1996).

* The Ilex-Myrcia Elfin Thicket community is 1.5-2.0 m tall and is dominated by evergreen microphyllous and nanophyllous shrubs. It occurs at 1800-1970 m on Pico Turquino, the highest peak of the Sierra Maestra. Taxa include, in addition to the dominant species of Ilex and Myrcia, Peratanthe, Myrica, Lobelia, Eupatorium, Vernonia, Weinmannia, Persea, Lyonia, Torralbasia and Viburnum. This community is related to "alpine thicket" of Beard, Knapp and Howard (Borhidi, 1996). An elfin woodland is described for Jamaica by Asprey and Robbins (1953). This type occurs at and above 5000 ft (1524 m) in the Blue Mountains, on exposed ridges and summits. It is an open woodland of low-branching, gnarled and twisted trees, often short, windblown and covered with mosses, lichens, ferns and other vascular epiphytes. Leaves are fleshy (Clusia and Hedyosmum), tomentose (Clethra) or small and coriaceous (Eugenia and Ilex). Dominant trees are Clethra alexandri and Clusia havetioides; some common trees are Vaccinium meridionale, Podocarpus urbanii, Cyrilla racemiflora, Eugenia alpina, Weinmannia pinnata and Ilex montana. There are shrubs, a field layer, bryophytes festooned from trees, which also support vascular epiphytes.

* The Agave pendentata--Mitrocarpus acuna community dominates an evergreen dwarf scrub 50-100 cm tall on the steep, rocky slopes of Pico Turquino, Sierra Maestra, Cuba. Agave is an emergent. The shrub layer dominates with Ilex, Mitracarpus, Cassia, Juniperus saxicola, Schoepfia Vernonia, Micromeria and Eugenia, plus herbs and Chusquea abietifolia, a vine bamboo (Borbidi, 1996).

2. South Florida and the Bahamas

Caribbean Pine Woodland (Pinus caribaea) is a type of flatwood that bears many similarities to the South Florida Slash Pine / Palm community. It occurs on limestone on the northern islands of the Bahamas. The following description is from personal notes taken on Grand Bahama Island, at Rand Memorial Nature Centre, on April 15, 1998. Under a variably spaced canopy of Caribbean pines the following small trees were identified: palms, Coccothrinax sp. and Thrinax morrisii; dicots, Manilkara zapota, Byrsonima lucida, Lysiloma latisiliqua, Swietenia mahagoni, Tabebouia bahamensis, Erithalis fruticosa, Exothea paniculata and Guettarda krugii. Common shrubs were Plumeria obtusa and Calliandra haematomina; some common herbs, Pteridium sp., Psilotum nudum and Uniola virgata.

3. Puerto Rico

For Puerto Rico, Weaver (1994) compiled the biota of Lower and Upper Montane zones of a natural area in the Luquillo Mountains. He listed the following "rare and endangered tree species of Puerto Rico found on permanent plots in the 'Colorado'" (Cyrilla racemiflora) forest: Ardisia luquillensis (Myrsinaceae); llex sintenisii (Aquifoliaceae); Ditta myricoides (Euphorbiaceae); Byrsonima wadsworthii (Malpighiaceae); Eugenia eggersii (Myrtaceae); Magnolia splendens (Magnoliaceae); Marlierea sintenisii Maytenus elongata, Cleyera albopunctata, Ternstroemia heptasepala and Z luquillensis (all Theaceae); Xylosma sehwaneckeanum (Flacourtiaceae); and Ouratea striata (Ochnaceae). Forty-one percent of the tree species are distributed on the mainlands of South America, Central America, Mexico, and Florida, 28% are found in the West Indies but not on the mainland, and 31% are endemic to Puerto Rico (Weaver, 1989).

E. RELATED VEGETATION IN BAJA CALIFORNIA SUR, MEXICO

In the Sierra de la Laguna (23[degrees]21 'N to 23[degrees]44'N and 109[degrees]44'W to 110[degrees]10'W), near La Paz, at the southern tip of the Baja California Peninsula in Mexico, there is a belt of evergreen oak forest between 770 m and 1200 m asl. The dominants are Quercus tuberculata, with Q. devia, Quereus oblongifolia (deciduous) and Q. arizonica. These form a canopy layer 10-20 m tall. Occasional individuals of Arbutus peninsularis, Prunus serotina subsp, virens and Heteromeles arbutifolia occur in protected or higher sites. Erythrina flabelliformis, Bursera microphylla, Bumelia peninsularis, Randia megacarpa (Leon de la Luz et al., 1988) and Lysiloma candida (Morelos O., 1988) occur in lower and more exposed sites in this forest. The shrub layer is dominated by Dodonaea viscosa, with Arracacia brandegeei (Apiaceae), Mimosa xantii, Tephrosia cana and Bernardia lagunensis (Euphorbiaceae). Other shrubs, more common in upper-elevation (>1200 m) forests of pine and oak, are species ofDalea, Garrya, Ilex, Phyllanthus, Rhus, Ribes and Styrax. The grass Heteropogon contortus, dominates the herbaceous layer. Other members of the herbaceous layer are Cnidoscolus angustidens, Croton spp., Indigofera fruticosa, Russelia retrosa, Cryptantha sp., Acalypha comonduana, Buddleia crotonoides and Jatropha vernieosa. Below about 900 m asl, in canyons and along streams, are found the palms Erythea brandegeei and Washingtonia robusta, the poplar Populus brandegeei and the endemic oak Quercus brandegeei.

In the dominance of evergreen oaks and the occurrence of palms and tropical hardwoods in warmer portions of the range, and the occasional deciduous tree in wetter or cooler sites, this mountain oak forest resembles the temperate broad-leaved evergreen, oak-dominated forest of Florida.

VI. Conclusions

Greller (1980) recognized one zonobiome and two zonoecotones for the TBEF region. He designated these ZB V, ZE V/II, and ZE V/VI. These are, respectively, the central TBEF in peninsular and coastal panhandle Florida, the TBEF transition to the Tropical Semi-Deciduous Woodland of South Florida and the TBEF transition to the Southern Mixed Hardwood Forest Association (or Deciduous-Evergreen-Conifer [DEC] zonobiome of Greller 1989) in northern Florida. ZB V and ZE V/VI continue north of Florida through southeastern Georgia and north along the Atlantic Coast to North Carolina. They also continue westward along the Gulf Coast at least to central Louisiana. Forest patches dominated by evergreen oaks and some deciduous trees occur widely within a prairie matrix in the Chenier region of southwestern Louisiana, continuing southward into the Texas Prairie region along the Gulf Coast. Phytogeographical affinities of these regions remain to be fully determined.

Greller (2000) recognized the Atlantic and Gulf Coastal Plains Floristic Province as one of two provinces in a proposed "Southeastern North American Region" of the Madrean Subkingdom of the Holarctic Kingdom (cf. Takhtajan, 1986). Most of the plants occur in all or parts of a U-shaped area coinciding with the Atlantic and Gulf Coastal Plains and extending northward in the Mississippi Valley to Indiana. Takhtajan included all but the southern tip of Florida in the province. An important local area of endemism is along the lower Apalachieola River in western Florida and adjacent Georgia (in the Southern Mixed Hardwood Forest region [ZE VI/V]; DEC of Greller, 1989), with 33 species, varieties or subspecies listed by Wunderlin (1998) as endemic to Florida. In addition, 13 more taxa occur in the Appalachicola region and in the Florida peninsula. Another, larger and richer, area of Florida endemism is the peninsular region, north of Dade and Monroe Counties, east of Madison and Taylor Counties, with the northern limit roughly in St. Johns, Putnam, Alachua, Gilchrist and Dixie Counties. Wunderlin (1998) lists 113 species, subspecies or varieties as Florida endemics in the peninsula region, including taxa confined to one or both coasts. Based on these data and data on related endemic vegetation, I propose that the Apalachicola River region (Apalachicolan) and peninsular Florida (Central Floridian) be treated as separate subprovinces of the Atlantic and Gulf Coastal Plain Province. Separate phytoehoria should be established for the montane areas of the Greater Antilles and the cold-influenced, northern Bahaman and Caribbean Basin regions that are characterized by the presence of Holarctic, Madrean-Tethyan flora and vegetation. Perhaps these could be united in a Caribbean-Antillean Province of the (proposed) Southeastern North American Region of Greller (2000). In Baja California Sur, a lower montane evergreen oak forest, with mixed Holarctic and neotropical trees, shrubs and herbs, may well deserve treatment as a subprovince of the Sierra Madre Occidental Province of the Madrean Region (cf. Greller, 2000). In their treatment of "Endangered Ecosystems of the United States," Noss et al. (n.d.) list the following vegetation types that are treated within the Central Floridian Province and in closely related phytochoria: "dry prairies of Florida," "Texas prairie," "wet and mesic coastal prairies in Louisiana," and "conversion of barrier island habitats (all types) on Atlantic and Gulf coasts to urban area." These vegetation types deserve special consideration for conservation measures.

Greller (1980) showed that winter temperatures were most closely congruent with boundaries of the Florida zonobiomes and zonoecotones. The implication of this finding is that rising winter temperatures, as a possible consequence of increasing atmospheric carbon dioxide concentrations, will result in the extirpation of temperate tree taxa within the political boundary of Florida. Box et al. (1999) used a previously developed plant species-climate envelope model to predict the effects of hypothesized climatic change on the potential distribution of 124 native woody plant species in Florida. They concluded that "large decreases in the Florida range of many temperate species would result" with 1-2[degrees]C increases in annual temperatures.
Table I
Florida endemics of Apalachicola and
the remainder of the panhandle region

Family Genus Species

Acanthaceae Justicia angusta
Acanthaceae Justicia crassifolia
Alismataceae Echinodorus floridanus
Amaryllidaceae Hymenocallis godfreyi
Amaryllidaceae Hymenocallis henryae
Apiaceae Oxypolis filiformis
Asteraceae Aster spinulosus
Asteraceae Boltonia apalachicolensis
Asteraceae Chrysopsis lanuginosa
Asteraceae Chrysopsis linearifolia
Asteraceae Liatris provincialis
Asteraceae Pityopsis flexuosa
Asteraceae Verbesina chapmanii
Clusiaceae Hypericum chapmanii
Clusiaceae Hypericum exile
Clusiaceae Hypericum lissophloeus
Ericaceae Rhododendron minus
Eriocaulaccae Eriocaulon nigrobracteatum
Euphorbiaceae Euphorbia telephioides
Fabaceae Baptisia calycosa
Fabaceae Baptisia simplicifolia
Fabaceae Lupinus westianus
Gentianaceae Gentiana pennelliana
Lamiaceae Conradina glabra
Lamiaceae Hedeoma graveolens
Lamiaceae Macbridea alba
Lentibulariaceae Pinguicula ionantha
Liliaceae Harperocallis flava
Linaceae Linum westii
Lythraceae Cuphea aspera
Magnoliaceae Magnolia macrophylla
Nymphaeaceae Nuphar lutea
Poaceae Sorghastrum apalachicolense
Potamogetonace Potamogeton floridanus
Sapotaceae Sideroxylon thornei
Taxaceae Taxus floridana
Taxaceae Torreya taxifolia
Xyridaceae Xyris longisepala

 Subspecies;
Family variety Locale

Acanthaceae Apalachicola
Acanthaceae Apalachicola
Alismataceae Panhandle; Escambia
Amaryllidaceae Apalachicola
Amaryllidaceae Apalachicola
Apiaceae ssp. greenmanii Apalachicola
Asteraceae Apalachicola
Asteraceae Apalachicola
Asteraceae Apalachicola
Asteraceae linearifolia Apalachicola
Asteraceae Apalachicola
Asteraceae Apalachicola
Asteraceae Apalachicola
Clusiaceae Apalachicola; panhandle
Clusiaceae Apalachicola; panhandle
Clusiaceae Apalachicola; panhandle
Ericaceae chapmanii Apalachicola
Eriocaulaccae Apalachicola
Euphorbiaceae Apalachicola
Fabaceae villosa Panhandle; Holmes
Fabaceae Apalachicola
Fabaceae westianus Coastal Apalachicola
Gentianaceae Apalachicola; Walton
Lamiaceae Panhandle
Lamiaceae Apalachicola
Lamiaceae Apalachicola
Lentibulariaceae Apalachicola
Liliaceae Apalachicola
Linaceae Apalachicola; panhandle
Lythraceae Apalachicola
Magnoliaceae ashei Apalachicola; panhandle
Nymphaeaceae ssp. ulvacea Panhandle
Poaceae Apalachicola
Potamogetonace Panhandle; Santa Rosa
Sapotaceae Apalachicola; Georgia
Taxaceae Apalachicola
Taxaceae Apalachicola; Georgia
Xyridaceae Apalachicola; panhandle

Table II
Florida endemics in both the peninsular and
the panhandle (mainly Apalachicola) regions

Family Genus Species

Agavaceae Nolina atocarpa
Alismataceae Sagittaria kurziana
Asteraceae Berlandiera subacaulis
Asteraceae Coreopsis floridana
Asteraceae Coreopsis leavenworthii
Asteraceae Eupatorium mikanioides
Asteraceae Liatris tenuifolia
Asteraceae Pluchea longifolia
Brassicaceae Rorippa floridana
Campanulaceae Campanula floridana
Commelinaceae Cuthbertia ornata
Euphorbiaceae Chamaesyce cumulicola
Poaceae Calamovilfa curtissii
Polygonaceae Polygonella robusta

Family Variety Locale

Agavaceae Peninsula; Apalachicola
Alismataceae Peninsula; Apalachicola
Asteraceae Peninsula; Apalachicola
Asteraceae Peninsula; Apalachicola
Asteraceae Peninsula; Apalachicola
Asteraceae Peninsula; Apalachicola
Asteraceae quadriflora Peninsula; Apalachicola
Asteraceae Peninsula; Apalachicola
Brassicaceae Peninsula; Apalachicola
Campanulaceae Peninsula; Apalachicola
Commelinaceae Peninsula; Apalachicola
Euphorbiaceae Peninsula; Escambria
Poaceae Peninsula; North Carolina
 to the panhandle
Polygonaceae Peninsula; Apalachicola

Table III
Florida endemics in the peninsular region
(wide and narrow distributions combined)

Family Genus Species

Acanthaceae Elytraria caroliniensis
Acanthaceae Justicia cooleyi
Agavaceae Agave decipiens
Agavaceae Nolina brittoniana
Amaryllidaceae Hymenocallis palmeri
Amaryllidaceae Zephyranthes simpsonii
Annonaceae Asimina obovata
Annonaceae Asimina reticulala
Annonaceae Asimina tetramera
Annonaceae Deeringothamnus pulchellus
Annonaceae Deeringothamnus rugelii
Aquifoliaceae Ilex opaca
Arecaceae Sabal etonia
Asclepiadaceae Asclepias curtissii
Asclepiadaceae Asclepias feayi
Aspleniaceae Asplenium xcurtissii
Aspleniaceae Asplenium xplenum
Asteraceae Arnoglossum floridanum
Asteraceae Carphephorus carnosus
Asteraceae Chrysopsis latisquamea
Asteraceae Chrysopsis linearifolia
Asteraceae Chrysopsis subulata
Asteraceae Flaveria floridana
Asteraceae Garberia heterophylla
Asteraceae Helianthus carnosus
Asteraceae Helianthus debilis
Asteraceae Liatris garberi
Asteraceae Liatris ohlingerae
Asteraceae Verbesina heterophylla
Brassicaceae Warea amplexifolia
Brassicaceae Warea carteri
Bromelliaceae Tillandsia simulata
Cactaceae Harrisia aboriginum
Campanulaceae Campanula robinsiae
Campanulaceae Lobelia feayana
Campanulaceae Lobelia homophylla
Cistaceae Helianthemum nashii
Cistaceae Lechea cernua
Cistaceae Lechea divaricata
Clusiaceae Hypericum cumulicola
Clusiaceae Hypericum edisonianum
Commelinaceae Commelina diffusa
Convolvulaceae Bonamia grandiflora
Convolvulaceae Jacquemontia curtisii
Convolvulaceae Jacquemontia reclinata
Convolvulaceae Stylisma abdita
Euphorbiaceae Croton glandulosus
Euphorbiaceae Euphorbia polyphylla
Euphorbiaceae Phyllanthus liebmannianus
Fabaceae Baptisia calycosa
Fabaceae Centrosema arenicola
Fabaceae Clitoria fragrans
Fabaceae Crotalaria avonensis
Fabaceae Dalea pinnata
Fabaceae Indigofera miniata
Fabaceae Lupinus westianus
Fabaceae Rhynchosia cinerea
Fabaceae Tephrosia rugelii
Fabaceae Vicia ocalensis
Fabaceae Quercus inopina
Juglandaceae Carya floridana
Lamiaceae Conradina etonia
Lamiaceae Dicerandra chrisimanii
Lamiaceae Dicerandra cornutissima
Lamiaceae Dicerandra frutescens
Lamiaceae Dicerandra thinicola
Lauraceae Persea borbonia
Linaceae Linum carteri
Loganiaceae Spigelia loganioides
Lythraceae Lythrum flagellare
Oleaceae Chionanthus pygmaeus
Oleaceae Osmanthus megacarpus
Orchidaceae Triphora latifolia
Orchidaceae Triphora rickettii
Poaceae Digitaria floridana
Poaceae Digitaria simpsonii
Poaceae Echinochloa paludigena
Poaceae Eustachys neglecta
Poaceae Panicum abscissum
Poaceae Piptochaetium avenacioides
Poaceae Schizachyrium niveum
Poloygalaceae Polygala lewtonii
Poloygalaceae Polygala smallii
Polygonaceae Eriogonum longifolium
Polygonaceae Polygonella basiramia
Polygonaceae Polygonella myriophylla
Polygonaceae Polygonella polygama
Ranunculaceae Clematis baldwinii
Rhamnaceae Ziziphus ciliata
Rubiaceae Spermadoce terminalis
Sapotaceae Sideroxylon alachuense
Sapotaceae Sideroxylon reclinatum
Scrophulariaceae Micranthemum glomeratum
Verbenaceae Glandularia maritima
Verbenaceae Glandularia tampensis
Verbenaceae Lantana depressa

 Variety;
Family subspecies Locale

Acanthaceae angustifolia Peninsula, southern
Acanthaceae Peninsula, north central
Agavaceae Peninsula
Agavaceae Peninsula
Amaryllidaceae Peninsula
Amaryllidaceae Peninsula
Annonaceae Peninsula
Annonaceae Peninsula
Annonaceae Peninsula
Annonaceae Peninsula
Annonaceae Peninsula
Aquifoliaceae arenicola Peninsula
Arecaceae Peninsula
Asclepiadaceae Peninsula
Asclepiadaceae Peninsula
Aspleniaceae Peninsula, north central
Aspleniaceae Peninsula, north central
Asteraceae Peninsula
Asteraceae Peninsula
Asteraceae Peninsula
Asteraceae dreasii Peninsula
Asteraceae Peninsula
Asteraceae Peninsula
Asteraceae Peninsula
Asteraceae Peninsula, northern
Asteraceae vestitus Peninsula, west central
Asteraceae Peninsula
Asteraceae Peninsula
Asteraceae Peninsula, northern
Brassicaceae Peninsula
Brassicaceae Peninsula
Bromelliaceae Peninsula
Cactaceae Peninsula, north central
Campanulaceae Peninsula; Hernando
Campanulaceae Peninsula
Campanulaceae Peninsula
Cistaceae Peninsula
Cistaceae Peninsula
Cistaceae Peninsula
Clusiaceae Peninsula
Clusiaceae Peninsula
Commelinaceae gigas Peninsula
Convolvulaceae Peninsula
Convolvulaceae Peninsula
Convolvulaceae Peninsula, southern
Convolvulaceae Peninsula
Euphorbiaceae Peninsula
Euphorbiaceae Peninsula
Euphorbiaceae ssp. platylepis Peninsula, northern
Fabaceae calycoso Peninsula
Fabaceae Peninsula
Fabaceae Peninsula
Fabaceae Peninsula
Fabaceae adenopoda Peninsula
Fabaceae florida Peninsula
Fabaceae aridorum Peninsula
Fabaceae Peninsula
Fabaceae Peninsula
Fabaceae Peninsula, northern
Fabaceae Peninsula
Juglandaceae Peninsula
Lamiaceae Peninsula; Putnam
Lamiaceae Peninsula; Highlands
Lamiaceae Peninsula
Lamiaceae Peninsula; Polk and
 Highlands
Lamiaceae Peninsula; Brevard
Lauraceae humilis Peninsula
Linaceae smallii Peninsula
Loganiaceae Peninsula
Lythraceae Peninsula
Oleaceae Peninsula
Oleaceae Peninsula
Orchidaceae Peninsula; Hillsborough
Orchidaceae Peninsula, north central
Poaceae Peninsula; Hernando
Poaceae Peninsula; Sarasota and
 Volusia
Poaceae Peninsula
Poaceae Peninsula, northern and
 central
Poaceae Peninsula
Poaceae Peninsula
Poaceae Peninsula
Poloygalaceae Peninsula
Poloygalaceae Peninsula
Polygonaceae Peninsula
Polygonaceae Peninsula; Polk and
 Highlands
Polygonaceae Peninsula
Polygonaceae brachystachy Peninsula
Ranunculaceae Peninsula
Rhamnaceae Peninsula
Rubiaceae Peninsula, eastern and
 south central
Sapotaceae Peninsula, north central
Sapotaceae ssp. rufotomen- Peninsula
 tosum
Scrophulariaceae Peninsula
Verbenaceae Peninsula
Verbenaceae Peninsula
Verbenaceae floridana Peninsula


VII. Acknowledgments

I am grateful to the Florida Department of Parks and the Virginia Department of Parks for permission to conduct research, to Stewart Ware and James Trent for companionship in the field and to Richard Wunderlin for reading an early draft of the article. I also thank the Interlibrary Loan Office of the Rosenthal Library, Queens College, for obtaining a number of hard-to-locate books and circulars. Special thanks go to Ann F. Johnson, who generously shared her encyclopedic knowledge of Florida vegetation and flora with me.

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ANDREW M. GRELLER

Department of Biology

Queens College, CUNY

Flushing, NY, U.S.A. 11367

and

The Graduate Center

The City University of New York

New York, NY, U.S.A. 10016
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Date:Jul 1, 2003
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