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Geographical distribution of wild Lactuca species (Asteraceae, Lactuceae).

 I. Abstract
 II. Introduction
 III. Geographical Distribution Analysis
 IV. Delimitation of the Genus Lactuca L.
 V. Natural Distribution Areas of Wild Lactuca Species
 A. European Species and Species with Circumglobal Distributions
 1. Lactuca serriola
 2. Lactuca saligna
 3. Lactuca virosa
 B. Remaining Closely Related Lactuca Species
 1. Lactuca quercina
 2. Lactuca tatarica
 3. Lactuca sibirica
 4. Lactuca perennis
 C. Remaining European Lactuca Species
 D. Asian Species
 E. African Species
 F. American Species
 VI. Conclusions
 VII. Acknowledgments
VIII. Literature Cited


I.

II. Introduction

The genus Lactuca is classified in the Asteraceae, subfamily Cichorioideae, tribe Lactuceae Cass., subtribe Lactucinae Dumort (Bremer et al., 1994). The family Asteraeeae has a worldwide distribution (Heywood, 1978), with about 1535 currently accepted genera and 23,000 species (Judd et al., 1999). Generic limits are often problematic, and several large genera are frequently divided into numerous segregates (Bremer et al., 1994). The family is divided into 17 tribes, which are often arranged into 3 subfamilies (Judd et al., 1999). Tribe Lactuceae (= Cichorieae) is characterized by ligulate capitula and copious milky latex and is divided into 11 subtribes, represented by 98 genera and more than 1550 species. Subtribe Lactucinae comprises 17 genera, including Lactuca, and ca. 270 species (Bremer et al., 1994). Frietema (1994) considered the common (vernacular) name of the species belonging to the genus Lactuca to be "lettuce." The genus Lactuca is represented by a range of forms, including annual, biennial, and perennial, glabrous or pubescent herbs with abundant latex, rarely shrubs, rhizomatous, sometimes with underground stolons or with fusiform and/or tuberous roots. The generic concept of Lactuca was well elaborated by Ferakova (1977), at least for European species. However, the complex of Lactuca spp. originating on other continents is not very well elucidated from a taxonomic viewpoint. A classification of these species, based on taxonomic and geographical concepts, was elaborated by Lebeda (1998) and Lebeda and Astley (1999). In this classification the genus is divided into seven sections and two (African and North American) geographical groups. Recently, the genus concept was discussed in detail by Koopman et al. (1998).

The genus Lactuca is distributed in temperate and warm regions, mostly in the Northern Hemisphere (Europe, Asia, Indonesia, North and Central America, Africa). Most of the species are xerophytes, well adapted to dry climatic conditions, except for some scandent, liana-like endemic species of the central African mountains (Ferakova, 1977). Ecologically Lactuca species are very diverse and occur in different habitats. Some more common European species (e.g., L. serriola, L. saligna, L. virosa) are frequently synanthropic (ruderal), preferring disturbed habitats (Lebeda et al., 2001a). However, some taxa (e.g., L. aurea, L. quercina, L. biennis, L. sibirica) are common in woodland habitats (Nessler, 1976; Ferakova, 1977). Some typical Mediterranean elements (e.g., L. intricata [syn. L. graeca], L. tenerrima, L. viminea subsp. alpestris) are commonly calciphilous plants often growing on rocky slopes (Lopez & Jimenez, 1974; Ferakova, 1977). The original habitat of L. acanthifolia is cliffs at the seashore. Lactuca tatarica grows in semiarid cold regions with steppe vegetation, mostly on salty meadows or sandy substrata; however, it is increasingly found as a weed in Asia and Europe (Ferakova, 1977; Jehlik, 1998).

Lactuca serriola (prickly lettuce), L. saligna (least lettuce), and L. virosa (great lettuce) are important in cultivated lettuce (L. sativa) breeding as donors of resistance genes (Lebeda, 1998; Ryder, 1998; Reinink, 1999; Sicard et al., 1999; Lebeda et al., 2002). On the basis of the gene-pool concept (Harlan & de Wet, 1971), Lactuca species were categorized into three gene pools based on their relationship to L. sativa (McGuire et al., 1993). The primary gene pool is represented by numerous cultivars of L. sativa, primitive landraces, and wild species where crossing barriers do not exist: first, L. serriola, which is probably the closest relative (progenitor) of L. sativa (de Vries, 1997); second, L. altaica, L. aculeata, L. azerbaijanica, L. georgica, L. scarioloides occurring in Asia, and L. dregeana from southern Africa. More distantly related Lactuca species are included in the secondary (L. saligna) and tertiary (L. virosa) gene pools (Zohary, 1991). On the basis of molecular studies, the species L. serriola, L. altaica, L. aculeata, and L. dregeana, which are closely related to L. sativa, are included in the primary gene pool; L. saligna and L. virosa belong to the secondary gene pool; the tertiary gene pool is represented by L. quercina, L. sibirica, L. tatarica, and L. viminea (Koopman et al., 1998; Koopman, 1999). These relationships were supported by the analysis of relative (Lebeda et al., 2001b; Dolezalova et al., 2002b) and absolute (Koopman et al., 2002) DNA content. The genetic resources of wild Lactuca spp. originating from primary and secondary gene pools are considered as very important sources of many characters in lettuce breeding (Boukema et al., 1990; McGuire et al., 1993; Lebeda, 1996, 1998; Ryder, 1998). However, currently only ca. 20% of the known species are available in the world Lactuca germplasm collections, and most of these species belong to the European geographical group (Lebeda et al., 2004). About 90-95% of all available wild Lactuca accessions represent three species (L. serriola, L. saligna, L. virosa) (Lebeda et al., 2004). It is evident that more detailed information on the biogeography and distribution is urgently needed for the future development of collecting strategies and for in situ and ex situ conservation. To date no world inventory or survey of Lactuca spp. from the geographical viewpoint is available.

The main aim of this article is to summarize all of the available data in the world literature on the occurrence and natural geographical distribution of wild Lactuca spp. and to contribute in more detail to knowledge of the phytogeography and biodiversity of this genus.

III. Geographical Distribution Analysis

An overview of the distribution of natural wild-growing Lactuca spp. has been developed from local floras in Europe and other regions, floras in wider geographical areas, articles on the general ecology and biogeography of Lactuca spp., and our ecogeographical observations made during collecting expeditions of Lactuca spp. germplasm to northern, central, and southern Europe (Dolezalova et al., 2001; Kristkova et al., 2001; Lebeda et al., 2001a). The distribution is characterized for each taxon and country, respectively. Recently accepted names of states and a geographical categorization of continents are used according to Lewis and Winkleman (1999); countries are specified according to the codes used for plant genetic resources documentation (Hintum, 1995). Regions and/or localities are used only as examples of ecological limits of distribution. Ecobiological data present only the basic and most important information explaining the distribution area. Pbytocoenological characteristics are not used in this article. Cultivated lettuce (Lactuca sativa L.) is not considered in the text because of its worldwide distribution and the information available on its many different forms (Rubatzky & Yamaguchi, 1997; Ryder, 1998; Jeffrey, 2001).

IV. Delimitation of the Genus Lactuca L.

In the taxonomic treatment of Lactuca, Ferakova (1977) reused the phrase that Babcock (1947) had applied to the genus Crepis as an "oscillation between splitting and lumping." This comment is still valid after almost 30 years after Ferakova's (1977) revision of Lactuca in Europe because the generic delimitation is still in question.

The most important characters used to define the Lactuca taxa are: cylindrical involucre of several rows of upright and rigid or reflexed bracts, receptacle without scales, corolla tube glabrous, collecting hairs on style arms long and prominent, homomorphic, distinctly but moderately compressed and many-ribbed beaked (rarely unbeaked) achenes, pappus of many fine simple smooth or scabrid bristles without (exceptionally with) an outer ring of very short, smooth hairs. According to Kilian (2001), in the circumscription of Lactuca in particular, three features have been strongly emphasized: the presence or absence of an outer row of minute pappus hairs; the presence or absence of a beak; and the number of flowers per capitulum.

Intergeneric transfers concern mainly species of the so-called related genera: from the subtribe Lactucinae Dumort (Cephalorrhynchus Boiss., Steptorhamphus Bunge); from the Sonchinae (Launaea Cass., Prenanthes L., Sonchus L., delimited by Boulos, 1972, 1973, 1974a, 1974b); and from the Crepidinae (Ixeris Cuss., Youngia Cass.). Some genera, such as Scariola F. W. Schmidt, Mulgedium Cuss., Cicerbita Wallr., rarely Mycelis Cass. are sometimes separated from Lactuca L. and at other times included.

The narrow generic concept of Lactuca has been supported by various authors. For example, Sojak (1961, 1962) accepted the genus Scariola and treated Lactuca subg. Mulgedium (Cass.) C. B. Clarke at the generic level as Lagedium Sojak (a genus in an intermediate position between Lactuca and Mulgedium), by Tuisl (1968) in Flora Iranica, and by Jeffrey (1975) in Flora of Turkey.

Bremer et al. (1994), in the list of genera belonging to the tribe Lactuceae, subtribe Lactucinae Dumort, comprising 270 species, followed the above-mentioned taxonomic approach, and, from the genera included as a whole or partly by some authors into Lactuca s.l., respected as separate Scariola F. W. Schmidt (10 species), Cicerbita Wallr. (35 sp.), Mulgedium Cass. (15 sp.), Mycelis Cass. (1 sp.), Lagedium Sojak (1 sp.). Also in the past twenty years have been described Asian genera with the majority of representatives in China: Notoseris C. Shih 1987, Pterocypsela C. Shih 1988, Paraprenanthes Chang ex C. Shih 1988, Lactucella E. A. Nazarova 1990, Chaetoseris C. Shih 1991, Stenoseris C. Shih 1991 (Shih, 1987, 1988a, 1988b, 1991; Nazarova, 1990). However, in many regional floras of central Europe (e.g., Adler et al., 1994; Rothmaler et al., 1999; Kubat et al., 2002) the broader generic concept of Lactuca (incl. Scariola and Lagedium) has been accepted.

In the decades after the treatment of the African taxa by Jeffrey (1966), of the European species by Ferakova (1977), of the European and Asian taxa in the former Soviet Union by Kirpicznikov (1964), and of the taxa in Turkey by Jeffrey (1975) and in Iran by Tuisl (1968), various new techniques were used in studies of individual taxa. Chromosome numbers were established--e.g., for L. longidentata (Arrigoni & Mori, 1976), L. palmensis (Ortega & Navarro, 1977), L. viminea subsp. chondrilliflora (Brullo & Pavone, 1978), L. viminea subsp. alpestris (Montmollin, 1986; Tzanoudakis, 1986), L. livida (Blanca Lopez & Cueto Romero, 1984), L. perennis subsp. granatensis, and L. viminea subsp. ramosissima (Mejias, 1993)--chromosome banding patterns were studied (Koopman et al., 1993), and new data on biochemical and molecular variability--e.g., isozyme and molecular markers in selected species--were generated by Kesseli and Michelmore (1986, 1996), but the results did not significantly influence the generic and infrageneric divisions. Koopman et al. (1998), in their article on phylogenetic relationships among Lactuca species and related genera based on ITS-1 DNA sequences, stated that the molecular data support the broader generic concept of Stebbins (1937b), supported by Ferakova (1977) but do not confirm the position of Lactuca subsect. Cyanicae DC. The taxa belonging to this taxonomic unit seem to be relatively unrelated to cultivated lettuce and the nominate subsection. Further phylogenetic studies using the new methodological approach are needed. According to Dolezalova et al. (2002b), the data on relative nuclear DNA contents correspond well with the recently accepted taxonomic classification of Lactuca.

In the present work we follow the wide generic concept of Lactuca and the subgeneric division suggested by Lebeda (1998), whereby seven sections and two heterogeneous geographical groups (African and North American) are recognized, until more facts on the natural relationship between individual representatives of the genus are collected.

The scientific names of wild Lactuca spp. are used according to the International Plant Names Index (IPNI) and Brummitt & Powell (1992) (Table I). The names according to former descriptions are used only in some cases where recent detailed taxonomic revision is absent. The text does not include morphological descriptions of individual species because of their availability in floras and determination keys. The taxonomic aspects are mentioned only in cases of geographical distribution and ecobiological importance. For some species under threat of genetic erosion, the areas of their distribution are reported to highlight the potential for in situ conservation at a national or international level. The potential and practical relevance of ex situ conservation is stressed.

V. Natural Distribution Areas of Wild Lactuca Species

Based on recent literature, the genus Lactuca L. comprises about 100 wild species; however, the number of taxa differs from author to author (Ferakova, 1977; Meusel & Jager, 1992; Bremer et al., 1994; Lebeda, 1998; Lebeda & Astley, 1999). The disagreements are caused by the broad biodiversity within the genus, by spontaneous hybridization, and by the fact that the large Lactuca genus includes chorologically strongly divergent groups of species.

There are 17 European, 40 Asian, 33 African, and 10 North American wild Lactuca species reported in the literature, most of which are confined to temperate and warm regions of the Northern Hemisphere (Ferakova, 1977; Rulkens, 1987; Lebeda & Astley, 1999), of which only 54 species are included in a world index of plant distribution maps (Lundqvist & Jager, 1995). However, our survey has shown that at least 98 wild Lactuca spp. are distributed around the world (Table I): 17 species in Europe, 51 in Asia, 43 in Africa, and 12 in the Americas (mostly North America). Some taxa (e.g., L. serriola, L. saligna), including Tasmania (Burbinge & Gray, 1970), are naturalized in Australia. The majority of Lactuca species are xerophytes, well adapted to dry climatic conditions, except for some scandent, liana-like endemic species of the central African mountains (Stebbins, 1937a; Dethier, 1982) and for eastern African species from subtropical and tropical rain forests and Madagascar (Jeffrey, 1966). In terms of the number of species, the genus Lactuca is especially rich in the African Tropics, in meridional Eurasia, and in eastern North America (Meusel & Jager, 1992) (Tables II-V).

In Europe, the genus reaches its western limit of distribution at approximately 9[degrees] W (L. tatarica). Lactuca saligna extends up to 70 W; and both L. serriola and L. virosa, to 5[degrees] W. The northern limits of the areas of many Eurasian species can be drawn between 50[degrees] and 55[degrees] N; L. tatarica extends to 67[degrees] N; and L. sibirica is found in some localities at 70[degrees] N (Ferakova, 1977). Central European species belong to sect. Lactuca. sect. Lactucopsis, and sect. Phoenixopus. Meridional (boreal)-continental Eurasian L. tatarica falls in the circumpolar-continental section Mulgedium (Ferakova, 1977; Meusel & Jager, 1992). The highest diversity of European Lactuca spp. occurs in the Mediterranean region, where all of the European representatives are found except for L. sibirica and L. altaica. Some taxa (L. viminea subsp. alpestris, L. acanthifolia, L. longidentata, L. watsoniana, L. livida, L. tenerrima, L. intricata) are strictly confined to this region (Table II).

The altitudinal range for the genus Lactuca extends in Europe from sea level to more than 2000 m; the taxa L. viminea subsp. alpestris, L. tatarica, L. altaica, L. tenerrima, and L. quercina subsp. wilhelmsiana have been recorded at elevations up to 2500 m. However, the optimum altitude for a majority of the species is 200-600 m (Ferakova, 1977; Lebeda et al., 2001a).

Most of the wild Lactuca species closely related to cultivated lettuce (L. sativa) are representatives of the section Lactuca L. concentrated in western Eurasia (Zohary, 1991; de Vries, 1997). The most common European taxa (L. serriola, L. saligna, L. virosa) and the southwestern Asian L. altaica, L. aculeata, L. azerbaijanica, L. georgica, and L. scarioloides belong to subsection Lactuca L. (Ferakova, 1977; Zohary, 1991; Lebeda, 1998). Lactuca serriola was naturally widespread in the south (the Orient, northwestern Africa) within meridional-temperate, western Eurasian areas of the distribution of the subsection Lactuca, while L. altaica had a northeastern distribution (Turkmenistan). Lactuca saligna occupies the Mediterranean South Atlantic-Pontic western part of the subsection distribution. The boundary of the original area of the third taxon, L. virosa, in central Europe has not been determined precisely because of its previous cultivation as a medicinal plant and its subsequent naturalization (Meusel & Jager, 1992).

The following section contains summaries of the distribution and ecobiology of the most important European Lactuca spp. (L. serriola, L. saligna, L. virosa, L. quercina, L. tatarica, L. perennis), which represent the primary, secondary, and tertiary gene pools of cultivated lettuce (L. sativa), of the remaining species of Europe, and of the species of Asia, Africa, and the Americas.

A. EUROPEAN SPECIES AND SPECIES WITH CIRCUMGLOBAL DISTRIBUTIONS

Seventeen wild Lactuca spp. occur in Europe (Tables I, II; Fig. 1).

I. Lactuca serriola

Lactuca serriola is the most variable and most widely distributed species of the genus (Tables II-V). It is a meridional-temperate, western Eurasian species; nevertheless, it now has a synanthropic worldwide distribution. Thus it has not been possible to determine the exact boundary of its original distribution area. It was domesticated in the Mediterranean and the Near East (de Vries, 1997) and is considered an arcbaeophyte dependent on a culture in the northern part of central Europe (Meusel & Jager, 1992). According to Clapham et al. (1962), it is "probably native" to England; and it is established as a fast-spreading synanthropophyte in Norway, Finland, and northern Russia (Mensel & Jager, 1992). According to Ferakova (1977), the northern boundary of the distribution area in Europe runs near latitude 65[degrees] N through Finland and 55[degrees] N through Great Britain. Its synanthropic distribution has been recorded from Australia, including Tasmania and New Zealand (Burbinge & Gray, 1970; Webb et al., 1988), and it is established as a weed in North America, southern Africa, and Argentina (Strausbaugh & Core, 1978; Boukema et al., 1990; Zohary, 1991; Zuloaga & Morrone, 1999).

Two main forms are recognized within Lactuca serriola, based on leaf-shape variability: L. serriola f. serriola, with pinnate-lobed leaves; and L. serriola f. integrifolia (S. F. Gray) S. D. Prince & R. N. Carter; with entire rosette and cauline leaves (Prince & Carter, 1977; Carter & Prince, 1982). This latter leaf form is also mentioned under synonyms L. serriola var. integrata Gren. et Godr., L. dubia Jord., and L. integrata A. Nels. (cf. Ferakova, 1977).

The f. serriola occurs throughout Europe, Asia, northern Africa, a greater part of North America, and Argentina (Tables II-V). The f. integrifolia is generally considered rare (Hegi, 1987); it is found throughout the L. serriola distribution area, but with different frequencies of occurrence. It is the dominant form in the British Isles (Prince & Carter, 1977; Lebeda, 1998, unpubl.; Lebeda et al., 2001a). Nowadays f. integrifolia is observed quite frequently in France (Lebeda et al., 2001a), and some records have been published in the Czech Republic, Germany, and Italy (Lebeda et al., 2001a) and also in the Netherlands (Van der Ham, 1981; Lebeda et al., 2001a). Nevertheless, its overall geographical distribution is poorly known (Lebeda et al., 2001a). Sporadic records exist from Slovakia and Turkey, both in the European and Asian areas (Ferakova, 1969, 1991, 2001, unpubl.). Plants with a densely setose inflorescence and spinoseciliate leaves described as a var. coriacea (Sch. Bip.) Rech. f. are restricted to the Mediterranean region (Ferakova, 1976). Moreover, a large proportion of the morphological variability of this species represent morphotypes with linear to narrowly oblong leaves resembling the species L. saligna.

From an orographic viewpoint, the northern boundary of Lactuca serriola is limited by warm summers (Meusel & Jager, 1992). It is distributed from lowland to montane regions (in Europe to 1560 m in Wallis (Switzerland); in Turkey to 1750 m; in Afghanistan to 3100 m; and in the northern Himalayas to 3600 m) (Hegi, 1987; Meusel & Jager, 1992). However, it is most frequently recorded at elevations of 200-600 m in Europe; above this altitude it is rather rare (Dosthlek, 1997; Ferakova, 1977; Dolezalova et al., 2001; Lebeda et al., 2001a). On the other hand, in Great Britain it is restricted to surprisingly low altitudes, seldom occurring above 80 m (Carter & Prince, 1985; Prince et al., 1985).

Recently, Lactuca serriola has spread throughout Europe as an invasive weed occupying ruderal places (Frietema de Vries et al., 1994). A significant expansion in the last two decades (Bowra, 1992) supports the general characteristic of this species, which is considered to be an "r" strategist, a pioneer plant of open habitats, spreading mainly with human activities (Mejias, 1994; Brant et al., 1999; Lebeda et al., 2001a). It is often recorded in pioneer plant communities.

2. Lactuca saligna

Lactuca saligna is widely distributed over the Mediterranean Basin and extends to the Caucasus and to temperate Europe as far as central Germany and southern Russia (Kirpicznikov, 1964; Jeffrey, 1975; Ferakova, 1976; Cvelev, 1989) (Table II). In Europe its distribution area reaches 52[degrees]N (Ferakova, 1977). It occurs as a facultative halophyte in western France, England, and Belgium, mostly at the seaside (Meusel & Jager, 1992) (Table II). Other common habitats include waste places, woodland borders, riverbanks, and arable fields (Ferakova, 1976, 1977; Lebeda et al., 2001a). Some, mostly historical, records from central Europe report the taxon in subhalophile meadows. It has been retreating in Europe, in spite of its inclination to spread in ruderal communities. Lactuca saligna is very rare in the Netherlands, Belgium, and England (Meusel & Jager, 1992). It is considered to be lacking species in the Czech Republic (Cerovsky et al., 1999; Grulich, 2002), not having been observed over the last two decades (Lebeda, 2001, unpubl.; Lebeda et al., 2001a) and as endangered in Austria (Adler et al., 1994). This species is rare in the greater part of its natural distribution area. However, it occurs in the Azores, the meridional-submeridional temperate Americas, California, Argentina, Australia, and Tasmania as a synanthropic plant (Burbinge & Gray, 1970; Meusel & Jager, 1992; Zuloaga & Morrone, 1999) (Table V). Its extra-European distribution includes Iraq, Iran, Saudi Arabia, and northern Africa (Rechinger, 1959; Tackholm, 1974; Feinbrun-Dothan, 1978; Hegi, 1987) (Tables III, IV).

Lactuca saligna is a characteristic weedy species of both lowland and hilly areas (Europe to 1000 m in Italy; Cyprus to 1680 m; Turkey to 2400 m) (Hegi, 1987; Meusel & Jager, 1992). Nevertheless, the most frequent occurrence of this species in Europe is at elevations between 0 and 300 m (Lebeda et al., 2001a).

3. Lactuca virosa

The submediterranean species Lactuca virosa occurs throughout Europe, mostly in the Mediterranean Basin (Mejias, 1993, 1994). In Europe it is distributed mainly in southwestern areas (Coutinho, 1974; Fournier, 1977; Pignatti, 1982; Rollan, 1985), ranging from Portugal and Spain northward to eastern England (Table II). Lactuca virosa is regarded as a spontaneous species in sandy dunes in England (Clapham et al., 1962). It can be found in ruderal habitats, such as roadsides and embankments (Lebeda & Astley, 1999); however, it may occur on limestone in the northern part of its distribution area (Meusel & Jager, 1992). This species was introduced as a medicinal plant into several European countries and to North America, where it became naturalized (Ferakova, 1977). It is generally considered rare in central Europe (Hegi, 1987; Sebald et al., 1996; Lebeda, 1998; Lebeda et al., 2001a). The study highlighted a temporary occurrence of L. virosa in Poland, Romania, and Hungary; however, it is not cultivated at present. Its historic synanthropic area is receding, and it is considered an endangered species in Niedersachsen (Germany) and in Austria (Meusel & Jager, 1992; Adler et al., 1994; Lebeda et al., 2001a). The species has not been found recently in the Czech Republic (Dostal, 1989; Lebeda et al., 2001a, unpubl.), Hungary (Soo, 1970), or Slovakia (Ferakova, 1977) (Table II).

Ferakova (1977) mentioned L. virosa as a common species in northern Africa (Morocco, Algeria, Lebanon, Tunisia) and in western Asia. Lactuca virosa is a thermophilous species distributed from lowland to submontane regions (central France to 1000 m; Wallis (Switzerland) to 1560 m; Morocco to 2300 m) (Hegi, 1987; Meusel & Jager, 1992). The subsp. cornigera (Pau et Font Quer) Emb. et Maire was reported in Morocco (Meusel & Jager, 1992).

B. REMAINING CLOSELY RELATED LACTUCA SPECIES

The distributions of the remaining closely related wild Lactuca species (L. aculeata, L. altaica, L. azerbaijanica, L. georgica, L. scarioloides) are centered in southwestern Asia (Table III), with the exception of L. dregeana, which is native in southern Africa (Table IV). Lactuca dregeana represents a case of long-distance dispersal from Eurasia to the southern tip of Africa (Zohary, 1991). The European part of the L. altaica distribution area is rather small and includes the lower Volga Basin. However, it is widely distributed over the steppe and semidesert areas of Soviet central Asia and extends to southwestern Siberia and to eastern and southern Transcaucasia (Kirpicznikov, 1964). Outside Europe it occurs in the Caucasus, Altai, Iran, China, and central and southwestern Asia (Pavlov, 1966; Ferakova, 1977; Ling & Shih, 1997) (Table III). The altitudinal distribution of L. altaica is very broad, extending from the lowest altitudes at sea level to montane areas up to 2000 m.

1. Lactuca quercina

Ferakova (1977) reported that L. quercina is related to Lactuca watsoniana (Azores) and L. aurea (Balkan peninsula) within the section Lactucopsis; nevertheless, the relationships are unclear in both cases. Some authors (e.g., Jeffrey, 1975) place the latter species in the genus Cicerbita as C. sonchifolia (Vis. et Panc.) Beauverd. Lactuca quercina is found in many widely scattered localities around its main southern submediterranean-North Pontic-Pannonic-Hercynian area, the result of the reduction of its distribution during the early Quaternary period (Meusel & Jager, 1992). Its occurrence in western Europe is of relict character. The western limit of the distribution area runs through France and the western part of central Germany. The main distribution area of this species reaches northward approximately to 52[degrees]N (one locality in Gotland is at 57[degrees]N); the eastern limit is formed by the Caspian Sea (50[degrees]E). It was also recorded in the Crimea and Asia Minor. Lactuca quercina subsp. quercina is replaced by L. quercina subsp. wilhelmsiana in the easternmost and southernmost parts of its area (Anatolia, the Caucasus) (Ferakova, 1976, 1977) (Table III).

Lactuca quercina is a woodland plant occurring from lowland to montane regions. In central Europe it is common at levels up to 700 m (Italy to 600 m; the Slovak Republic to 550 m). The taxon is found at its highest altitudes in the Caucasus (1800 m) (Meusel & Jager, 1992).

2. Lactuca tatarica

The distribution area of the section Mulgedium, represented mainly by Lactuca tatarica and L. sibirica, includes continental Europe and central Asia (Tables II, III). Lactuca tatarica occurs in areas of sandy (usually saline) substrata in semiarid regions, as well as in elements of steppe and littoral communities (Ferakova, 1976, 1977; Clement & Foster, 1994). There are two subspecies known within L. tatarica that apparently resemble each other; however, their distribution differs (Ferakova, 1977). Subspecies tatarica is distributed in Europe, while subspecies pulchella has an exclusively extra-European distribution (India, Mongolia, China, Alaska, and a greater part of North America) (Lindman, 1926; Hulten, 1968; Ferakova, 1977; Hulten & Fries, 1986; Hickman, 1993; Holmgren et al., 1998). Since the beginning of the twentieth-century L. tatarica has been widespread in southern and central areas around the Baltic Sea and has been naturalized in plant communities close to littoral vegetation. The distribution and history of naturalization of L. tatarica on the coast of the Baltic Sea in the former German Democratic Republic have been analyzed (Krisch, 1989). It is supposed that L. tatarica was brought to northern Europe by steppe cocks (Syrrhaptes paradoxus), according to Meusel and Jager (1992), with alluvia. Following Krisch's (1989) concept, it was unintentionally introduced in the ballast of sailing ships during the nineteenth century. Jehlik (1998) characterized it as a dangerous weed in arable fields in the former Soviet Union, and it has been spread with Soviet wheat in central Europe. The majority of localities in the Czech and Slovak Republics (ca 75%) represent the environs of railway stations and cereal stores (Jehlik, 1998).

The most common habitat of L. tatarica is unfertile soil with a high content of salt, strong summer insolation, and low winter temperatures. This species is recorded from high elevations (central Asia to 3400 m; Afghanistan to 3000 m; western Tibet, 2750-5000 m) (Meusel & Jager, 1992). A type with white florets and to a great extent sterile achenes from the Baltic island of Hidensee has been described as var. hidenseensis (Leick & Steubing, 1957).

3. Lactuca sibirica

The Eurasian Nordic species L. sibirica is considered part of the lettuce gene pool (Koopman, 1999). It occurs in the northern parts of Russia, Scandinavia, China, and Japan and also extends to North America (Lindman, 1964; Krasnoborov, 1997; Hamet-Ahti et al., 1998) (Tables II, III). The most common habitats are riverbanks, moist woods, roadsides, and waste places (Lindman, 1964; Ferakova, 1977; Hamet-Ahti et al., 1998).

4. Lactuca perennis

The primitive genome (Koopman et al., 1998, 2002; Dolezalova et al., 2002b), absence of crossability, and small intraspecific variability of Lactuca perennis underline its independence and great phylogenetic age (Slavik, 1966). Lactuca perennis occupies an isolated position in section Lactuca and, together with its stenochoric western and eastern Mediterranean relatives L. tenerrima and L. intricata, forms the subsection Cyanicae DC. (Ferakova, 1977). In general, phylogenetic studies have shown that subsect. Cyanicae is relatively unrelated to cultivated lettuce and that its position in the lettuce gene pool is questionable (Koopman, 1999).

This submediterranean montane species with slight suboceanic tendency prefers open, rocky substrata, especially limestone, and a long, warm vegetative period (Ferakova, 1976, 1977). Lactuca perennis has been found at subruderal localities along roads; however, its area of distribution is receding in central Europe owing to the destruction of natural habitats (Meusel & Jager, 1992). Its distribution in Europe is discontinuous. The northern limit of its distribution area can be drawn approximately between 50[degrees] and 51[degrees]N; the eastern limit runs through Bulgaria and Romania (Ferakova, 1976). The species is relatively frequent in Spain, France, and southeastern Belgium (Ferakova, 1976; Fournier, 1977; Rollan, 1985) (Table II). The subspecies granatensis Charpin et Fern. Casas, syn. L. singularis Wilmott, L. grosii (Pau & Font Quer) is regarded as an endemic in eastern Spain (Charpin & Casas, 1981; Meusel & Jager, 1992).

Lactuca perennis occurs at elevations ranging from lowland to subalpine regions (Bulgaria to 550 m; Italy to 2000 m; Wallis to 2120 m), and it is suited to fiver valleys (Tirol: Etsch, Eisack, Inn; Pannooia: Danube, Waag; western Germany: Rhein, Mosel, Main, Taubergebiet, Oberen Neckar, Oberen Donautal; central Germany: Saale, Elbe) and dry climates (Meusel & Jager, 1992; Sebald et al., 1996). Ferakova (unpubl. results) studied this species outside river valleys in the Slovak Republic and found the prevalence of its localities are in the Slovak karst.

C. REMAINING EUROPEAN LACTUCA SPECIES

The distribution areas of the remaining European taxa are rather small in comparison with those included in the Lactuca spp. gene pool; they are mostly considered endemics occurring in restricted regions (Table II). The exception is L. viminea, belonging to the meridional (mountain)-submeridional section Phoenixopus, which is sometimes separated as the genus Scariola (Tuisl, 1968; Rechinger, 1977). Lactuca viminea occupies the western part of the section area, while L. acanthifolia and L. longidentata are restricted to the Oriental-Turkestan-Altai region. The L. viminea area comprises almost the whole territory of Atlantic, southern, and central Europe, the Caucasus, Asia Minor, northern Africa, Palestine, Iraq, and Turkmenistan (Tables II, III). Four subspecies are recognized within L. viminea: subsp. viminea, subsp. alpestris, subsp. chodrilliflora, and subsp. ramosissima. Lactuca viminea subsp. viminea is a Eurasian taxon most prevalent in the Mediterranean area (Ferakova, 1977; Hegi, 1987). The recent reduction in the natural distribution of L. viminea subsp. viminea in central Europe (it is extinct in the former East Germany and potentially endangered in Austria) has been caused by reforestation of its natural habitats (Meusel & Jager, 1992). The subspecies grows on rocks, cliffs, and exposed slopes, in scrub and grass communities (Ferakova, 1977), in gravels, among stones, in waste places (Dolezalova, 2001, unpubl.), and often in old quarries (Ferakova, 2001, unpubl.). The distribution area of L. viminea subsp. chondrilliflora is restricted to the southernmost regions of France, namely the Rhone River Valley and the eastern part of France, Italy (Ferakova, 1977; Lebeda et al., 2001a), the Iberian Peninsula (Mejias, 1994), and isolated locations in Switzerland and Serbia (Ferakova, 1977). Dense populations occur along roads in ditches, among stones, and in vineyards (Lebeda et al., 2001a). Lactuca viminea subsp. ramosissima occurs frequently in France and the Iberian Peninsula (Lopez & Jimenez, 1974; Mejias, 1994). Lactuca viminea subsp. alpestris is considered an endemic in Crete, preferring sunny habitats, calcareous rocks, and elevations up to 2500 m (Ferakova, 1977).

D. ASIAN SPECIES

The Asian species are mostly representatives of the sections Tuberosae, Micranthae, and Sororiae, except for the above-mentioned species from the section Lactuca (Lebeda, 1998; Lebeda & Astley, 1999). Altogether, 51 Lactuca species are recorded in Asia (Tables I, III; Fig. 1), which represent about 52% of the total number of species in the genus. However, only a few species are distributed throughout the continent. The greatest species richness is recognized in Iran, India, and Pakistan (15, 18, and 23 species, respectively), while in some other countries (e.g., Mongolia, Israel, Lebanon, Syria) only a few (3-7) Lactuca spp. (Table III) are found.

Lactuca aculeata is restricted to the Near East. It is an Irano-Turanian steppe element occurring mostly among rocks and in uncultivated fields (Tuisl, 1968; Jeffrey, 1975). Lactuca scarioloides is distributed over eastern Turkey, Iraqi Kurdistan, Iran, and Afghanistan on high plateaus (2000-3000 m) (Tuisl, 1968; Jeffrey, 1975; Rechinger, 1977). Lactuca azerbaijanica is an endemic species known from a single location in Iranian Azerbaijan (Rechinger, 1977). The distribution of L. georgica is restricted to the wet Euxinian-Hyrcanian region of southwestern Asia (Caucasia, northeastern Anatolia, and northern Iran) (Kirpicznikov, 1964; Jeffrey, 1975). The most common species belonging to the section Tuberosae are L. indica, L. raddeana, and L. triangulata (Lebeda, 1998; Lebeda & Astley, 1999) (treated as subgenus Pterachaenium [Kitam.] Kirp. by Kirpicznikov [1964]). Lactuca indica var. laciniata occupies grassy places in the lowlands of Japan, Korea, China, Taiwan, and Indonesia; nevertheless, this species is original in Africa also (South Africa, Mozambique, Madagascar, Mauritius, Seychelles) (Jeffrey, 1966) (Table IV). Lactuca raddeana is distributed in the Russian Far East (Sakhalin, Kurilen), Japan, China, Taiwan, Indochina, and Korea. Lactuca triangulata occurs on mountain slopes of Japan, Sakhalin, Manchuria, and Korea (Kirpicznikov, 1964; Ohwi, 1965). Lactuca auriculata, L. dissecta, L. glauciifolia, and L. undulata are the representatives of the section Micranthae (Lebeda, 1998; Lebeda & Astley, 1999) with wide distribution areas. Lactuca auriculata occurs in different habitats (among stones, along rivers, as a weed, mostly above 2500 m) of central Asia (Iran, India, and the former Soviet Union) (Pavlov, 1966). Lactuca dissecta and L. glauciifolia are distributed in Iran, Pakistan, Afghanistan, India, China, and the former Soviet Union (Rechinger, 1977). Lactuca undulata is an Irano-Turanian element with occurrence in the eastern Mediterranean, Iraq, Pakistan, central Asia, and western China (Jeffrey, 1975).

Lactuca sororia is a relatively common wild lettuce of the section Sororiae occurring in Japan (Honshu, Kyushu, Shikoku) and China in deciduous forests (Iwatsuki et al., 1995); it grows in grasslands at lower elevations in the north of Taiwan (Hui-Lin et al., 1978).

E. AFRICAN SPECIES

According to Jeffrey (1966), the African group of Lactuca spp. is represented by 33 species. However, Lebeda and Astley (1999) pointed out that during the last two decades some new species have been recorded or determined. Our recent survey showed that at least 43 Lactuca species (Tables I, IV) are known on the African continent; that is, this is the second largest geographical group of Lactuca spp. About 75% of the Lactuca spp. (31 in all) occurring in Africa can be considered autochthonous (Tables I, IV; Fig. 1).

The group of African Lactuca spp. is very heterogeneous and represents species that occur mostly in tropical eastern Africa and Madagascar (Jeffrey, 1966; Jeffrey & Beentje, 2000); scandent, liana-like endemic species of the central African mountains (Stebbins, 1937a; Dethier, 1982); and species that are more widely distributed (L. serriola, L. saligna; Table IV). Recent analysis demonstrated that there are large differences in Lactuca spp. distribution among different areas of Africa (Table IV). Only eight species are reported in northern Africa; higher numbers of species are recorded from eastern Africa (18 spp.) and western tropical Africa (10 spp.); while the highest species richness is evident in central (23 spp.) and southern (23 spp.) Africa. Southern Africa is endowed with an unusually rich flora with high levels of endemism, assembled within vegetation types ranging from desert to rain forest (Cowling et al., 1997). Most of the African species are considered autochthonous elements (Lebeda, 1998; Lebeda & Astley, 1999) and are restricted to limited areas; for example, L. schulzeana to Cameroun, the Congo, and Uganda; L. homblei to the Congo and Zambia; and L. dregeana and L. tysonii to South Africa. Others, however (L. capensis, L. glandulifera, L. imbricata, L. lasiorhiza, L. schweinfurthii), are more widely distributed. Nevertheless, only limited information is available on the biology and ecology of the African species (Lebeda & Astley, 1999).

F. AMERICAN SPECIES

Based on the recent survey, 12 Lactuca spp. were recorded in the Americas (Table V). This group of species, classified as a North American group (Lebeda & Astley, 1999), includes species originating and distributed in North America (from Canada to Florida), as well as species that are synanthropic and cosmopolitan (L. serriola, L. saligna, L. virosa) (Steyermark, 1963; Nessler, 1976; Strausbaugh & Core, 1978; Cronquist, 1980; McGregor et al., 1986). Seven Lactuca spp. in North America can be considered autochthonous (Table V; Fig. 1). These species, genetically distant from other Lactuca spp., are characterized by the consistent presence of the haploid number of chromosomes (n = 17) (Babcock et al., 1937) and completely different relative DNA content (Lebeda et al., 2001b; Dolezalova et al., 2002b). Lactuca canadensis, L. graminifolia, L. biennis, and L. intybacea are the most common species in this area. Lactuca canadensis occurs throughout the greater part of the northeastern and north central United States and Canada in thickets, at the edges of woods, and in forest clearings (Fernald, 1950; Cronquist, 1980; McGregor et al., 1986; Hickman, 1993; Kartesz, 1994). Lactuca graminifolia is widespread in sandy fields, open woods, and clearings, mainly in North and South Carolina, Arizona, Texas, Florida, and Mexico (Cronquist, 1980); it was also recorded in Guatemala (Nash, 1976). Lactuca biennis is scattered throughout the Great Plains in forest clearings, along streams, and on lakeshores (McGregor et al., 1986). Lactuca intybacea is a characteristic species for Central America (Belize, Guatemala, Cuba, Bahamas) (Alain, 1964; Nash, 1976; Balick et al., 2000) and northern parts of South America (Venezuela, Peru) (Lasser, 1964; Brako & Zarucchi, 1993). In fact, this is the only wild Lactuca sp. that commonly occurs in this part of the Americas (Table V). It grows mainly on open banks or in dry thickets, and sometimes along sandy streambeds. Information about the occurrence of other Lactuca species in Central and South America is rather rare. Lactuca serriola and L. saligna are reported only in Argentina (Table V).

VI. Conclusions

The data summarized in article paper show that the genus Lactuca includes a relatively large number of species distributed in most of the world's important biogeographical and phytogeographical regions (Good, 1974; Cox & Moore, 1985). Notwithstanding, there are enormous differences in its continental distribution and biodiversity (Lebeda et al., 2004). This is the reason why there are not only lower taxonomic categories (section/subsection) specified in this genus but also fewer geographical groups (Lebeda & Astley, 1999) and less characterization according to occurrence of autochthonous species (African and North American group). Some species (e.g., L. serriola, L. saligna, L. virosa) have circumglobal distributions, while others (L. aculeata, L. azerbaijanica, L. floridana, L. intricata, L. georgica, L. scarioloides. etc.) occur in restricted distribution areas. Some taxa are regarded as direct progenitors of cultivated lettuce (L. sativa) (Zohary, 1991).

Plant systematics, as a discipline aimed at the classification of species, and the understanding of phylogeny and evolutionary relationships (Koopman, 1999) require verified data on phytogeography, distribution, ecology, and intraspecific variation. Such complex information could also be used to better elaborate the generic concept. From our recent data it is evident that we are lacking such information for Lactuca L. This information is not only important for plant taxonomists and biologists but also an useful tool for the development of comprehensive strategies for the collection, regeneration, ex situ conservation, gene-bank management, and plant breeding (Guarino et al., 1995; Van Soest & Boukema, 1997; Koopman, 1999; Lawrence, 2002; Lebeda et al., 2004). Nevertheless, only limited valid information is available on the taxonomy of the genus Lactuca (Table I) and related genera (Lebeda & Astley, 1999; Lebeda et al., 2004). Field studies, surveys of occurrence, and collecting and maintenance of these species must be considered a priority for progress in research in areas such as the taxonomy and phytogeography of the genus Lactuca (Lebeda et al., 2004). Certainly, comprehensive data on the geographical distribution and ecobiology of the African, Asian, and North American Lactuca spp. are absent. These taxa are not treated in monographs, as European species are (see Ferakova, 1977), and in many cases we are lacking basic taxonomic descriptions, determination keys, and ecobiological data. A good knowledge of taxonomy is considered a most important prerequisite, not only for taxonomists and biogeographers but also for the efficient management and utilization of Lactuca germplasm collections (Lebeda et al., 1999, 2004). It is well documented that many wild Lactuca spp. accessions maintained in herbaria and gene-bank collections are not correctly determined (Lebeda & Astley, 1999; Lebeda et al., 2001b; Dolezalova et al., 2003b, 2004). It has also been stressed that taxonomic validation (at the level of species and subspecies) of recently collected wild Lactuca spp. genetic resources is urgently needed. Such work must be based on classical taxonomy and the use of original herbarium specimens (Lebeda et al., 2004). However, there was no optimal format for voucher herbarium specimens for wild taxa until Koopman (2002) developed a model voucher system for Lactuca L. A similar situation has characterized basic morphological descriptions of genetic resources of wild Lactuca spp. (Dolezalova et al., 2002a, 2003a). Lebeda et al. (1999, 2004) suggested the creation of a world monograph of the genus Lactuca, including taxonomical, phytogeographical, and ecogeographical data and information on available genetic resources in order to promote research on and utilization of these wild taxa.

At the global level, four recently developed programs may provide substantial contributions to the above strategy: the International Lactuca Database (ILDB, 2001; Stavelikova et al., 2002); the Millennium Seed Bank Project, the international collaborative seed conservation effort for wild plant species (Alton & Linington, 2001); the Global Biodiversity Information Facility (GBIF), which has been launched to collate information on the world's most important collections of animal and plant species (Kenyon, 2001); and the Strategy of Collaboration between the Botanic Gardens and Agricultural Genebanks (Engels & Engelmann, 2002).
Table I
Overview of the continental location of wild Lactuca spp., based on
floras.

Kev: + = present

 Continental location

Lactuca spp. (a) Europe Asia Africa

L. acanthifolia (Willd.) Boiss. + +
L. aculeata Boiss. et Kotschy +
L. altaica Fisch. et C. A. Mey. + +
L. ambacensis (Hiern) C. Jeffrey +
L. attenuate Stebbins +
L. aurea (Sch. Bip. ex
 Vis. et Panc.) Stebbins +
L. auriculata DC. +
L. azerbaijanica Rech. f. +
L. benthamii C. B. Clarke +
L. biennis (Moench) Fernald
L. bracteata Hook. f. et
 Thoms. ex C. B. Clarke +
L. brunoniana C. B. Clarke +
L. calophylla C. Jeffrey +
L. canadensis L.
L. capensis Thunb. +
L. cichorioides (Hiern) C. Jeffrey (b) +
L. cooperi Anthony +
L. crambifolia Boiss. (c) +
L. cubanguensis (S. Moore) C. Jeffrey +
L. decipiens C. B. Clarke +
L. dissecta D. Don +
L. dolichophylla Kitamura +
L. dregeana DC. +
L. dumicola S. Moore +
L. elgonensis Stebbins +
L. floridana (L.) Gaertn.
L. formosana Maxim. +
L. georgica Grossh. +
L. glandulifera Hook. f. +
L. glauciifolia Boiss. +
L. graciliflora DC. +
L. graminifolia Michx.
L. hirsuta Muhl. ex Nutt.
L. homblei De Wild. +
L. imbricata Hiern +
L. indica L. + +
L. inermis Forsk. + +
L. intricata Boiss. + +
L. intybacea Jacq. +
L. kashmiriana S. K.
 Mamgain et R. R. Rao +
L. laevigata DC. +
L. lahulensis S. K.
 Mamgain et R. R. Rao (b) +
L. lasiorhiza (O. Hoffm.) C. Jeffrey +
L. lessertiana C. B. Clarke +
L. livida Boiss. et Reut. +
L. longespicata Wildem. +
L. longidentata Moris +
L. ludoviciana Riddell
L. mwinilungensis G. V. Pope +
L. orientalis (Boiss.) Boiss. + +
L. palmensis C. Bolle +
L. paradoxa Sch. Bip. ex A. Rich. +
L. perennis L. +
L. persica Boiss. (c) +
L. petrensis Hiern +
L. picridiformis Boiss. (d) +
L. polyclada Boiss. +
L. praecox R. E. Fr. +
L. praevia C. D. Adams +
L. quercina L. + +
L. raddeana Maxim. (b) +
L. rapunculoides C. B. Clarke +
L. remotiflora DC. + +
L. rhynchocarpa Balf. f. +
L. rosularis Boiss. +
L. runcinata DC. +
L. saligna L. + + +
L. scarioloides Boiss. +
L. schulzeana Buettn. +
L. schsweinfurthii Oliver et Hiern +
L. scoparia Rech. et Koie +
L. serriola L. + + +
L. seticuspis Boiss. +
L. setosa Stebbins ex C. Jeffrey +
L. sibirica (L.) Benth. ex Maxim. + +
L. sikkimennis (Hook. f.) Stebbins (b) +
L. songeensis C. Jeffrey (b) +
L. sororia Miq. +
L. stebbinsii N. Kilian +
L. stipulata Stebbins +
L. takhtadzhianii Sosn. (d) +
L. taraxacifolia Schum. et Thonn. + (e) +
L. tatarica C. A. Mey. + +
L. tenerrima Pourr. + +
L. terrae-novae Fernald
L. tinctociliata I. M. Johnstott +
L. triangulata Maxim. +
L. triquetra Benth. et Hook. f. +
L. tuberosa A. Cheval +
L. tysonii (Phillips) C. Jeffrey +
L. ugandensis C. Jeffrey +
L. undulata Ledeb. + +
L. viminea (L.) J. et C. Presl + + +
L. violaefolia C. B. Clarke (b) +
L. virosa L. + +
L. wallichiana Tuisl +
L. watsoniana Trel. +
L. zambeziaca C. Jeffrey +

 Continental location

 Central
 North and South
Lactuca spp. (a) America America Australia

L. acanthifolia (Willd.) Boiss.
L. aculeata Boiss. et Kotschy
L. altaica Fisch. et C. A. Mey.
L. ambacensis (Hiern) C. Jeffrey
L. attenuate Stebbins
L. aurea (Sch. Bip. ex
 Vis. et Panc.) Stebbins
L. auriculata DC.
L. azerbaijanica Rech. f.
L. benthamii C. B. Clarke
L. biennis (Moench) Fernald +
L. bracteata Hook. f. et
 Thoms. ex C. B. Clarke
L. brunoniana C. B. Clarke
L. calophylla C. Jeffrey
L. canadensis L. +
L. capensis Thunb.
L. cichorioides (Hiern) C. Jeffrey (b)
L. cooperi Anthony
L. crambifolia Boiss. (c)
L. cubanguensis (S. Moore) C. Jeffrey
L. decipiens C. B. Clarke
L. dissecta D. Don
L. dolichophylla Kitamura
L. dregeana DC.
L. dumicola S. Moore
L. elgonensis Stebbins
L. floridana (L.) Gaertn. +
L. formosana Maxim.
L. georgica Grossh.
L. glandulifera Hook. f.
L. glauciifolia Boiss.
L. graciliflora DC.
L. graminifolia Michx. + +
L. hirsuta Muhl. ex Nutt. +
L. homblei De Wild.
L. imbricata Hiern
L. indica L.
L. inermis Forsk.
L. intricata Boiss.
L. intybacea Jacq. + +
L. kashmiriana S. K.
 Mamgain et R. R. Rao
L. laevigata DC.
L. lahulensis S. K.
 Mamgain et R. R. Rao (b)
L. lasiorhiza (O. Hoffm.) C. Jeffrey
L. lessertiana C. B. Clarke
L. livida Boiss. et Reut.
L. longespicata Wildem.
L. longidentata Moris
L. ludoviciana Riddell +
L. mwinilungensis G. V. Pope
L. orientalis (Boiss.) Boiss.
L. palmensis C. Bolle
L. paradoxa Sch. Bip. ex A. Rich.
L. perennis L.
L. persica Boiss. (c)
L. petrensis Hiern
L. picridiformis Boiss. (d)
L. polyclada Boiss.
L. praecox R. E. Fr.
L. praevia C. D. Adams
L. quercina L.
L. raddeana Maxim. (b)
L. rapunculoides C. B. Clarke
L. remotiflora DC.
L. rhynchocarpa Balf. f.
L. rosularis Boiss.
L. runcinata DC.
L. saligna L. + + +
L. scarioloides Boiss.
L. schulzeana Buettn.
L. schsweinfurthii Oliver et Hiern
L. scoparia Rech. et Koie
L. serriola L. + + +
L. seticuspis Boiss.
L. setosa Stebbins ex C. Jeffrey
L. sibirica (L.) Benth. ex Maxim.
L. sikkimennis (Hook. f.) Stebbins (b)
L. songeensis C. Jeffrey (b)
L. sororia Miq.
L. stebbinsii N. Kilian
L. stipulata Stebbins
L. takhtadzhianii Sosn. (d)
L. taraxacifolia Schum. et Thonn.
L. tatarica C. A. Mey. +
L. tenerrima Pourr.
L. terrae-novae Fernald +
L. tinctociliata I. M. Johnstott
L. triangulata Maxim.
L. triquetra Benth. et Hook. f.
L. tuberosa A. Cheval
L. tysonii (Phillips) C. Jeffrey
L. ugandensis C. Jeffrey
L. undulata Ledeb.
L. viminea (L.) J. et C. Presl
L. violaefolia C. B. Clarke (b)
L. virosa L. + + (f)
L. wallichiana Tuisl
L. watsoniana Trel.
L. zambeziaca C. Jeffrey

(a) Names of Lactuca species are modified
according to the recent status of IPNI (April 2003).

(b) Species are reported in local floras (see
Tables III, IV) only, not in IPNI (April 2003).

(c) Lactuca crambifolia and L. persica are sometimes
treated as genus Steptorhamphus (L. crambifolia (Bunge)
Boiss. = S. crambifolius Bunge; L. persica = S. persicus
(Boiss.) O. et B. Fedtsch.).

(d) Lactuca picridiformis and L. takhtadzhianii are
sometimes treated as genus Cephalorrhynchus (L.
picridiformis Boiss. = C. picridiformis (Boiss.) Tuisl;
L. takhtadzhianii Sosn. = C. takhtadzhianii (Sosn.) Kirp.).

(e) Lactuca taraxocifolia Khalk., recorded a new species
(Chalkuziev, 1974), has been not reported in local floras.
It has recently been considered as a synonym for L. altaica
S. S. Kovalevskaya (IPNI 2003).

(f) Lactuca virosa has been reported from New Zealand
(Webb et al., 1988).

Table II
Distribution of wild Lactuca spp. in European countries.

Key: ALB = Albania; AUT= Austria; BEL = Belgium; BGR = Bulgaria;
BIH = Bosnia and Herzegovina; CHE Switzerland; CZE = Czech Republic;
DEU = Germany; DNK = Denmark; ESP = Spain; FIN = Finland; FRA France;
GBR = Great Britain; GRC = Greece; HRV = Croatia; HUN = Hungary; ITA =
Italy; LUX = Luxembourg; MKD = Macedonia; NLD = Netherlands; NOR =
Norway; POL = Poland; PRT = Portugal; ROM = Romania; RUS = European
part of the former Soviet Union (recently the Russian Federation);
SVK = Slovak Republic (Slovakia); SVN = Slovenia; SWE = Sweden;
YUG = Yugoslavia; + = present.

 Country

Lactuca spp. ALB AUT BEL BGR BIH CHE CZE

L. acanthifolia
L. altaica
L. aurea +
L. intricata +
L. livida
L. longidentata
L. palmensis
L. perennis subsp.
 granatensis
L. perentinis subsp. + + + + + + +
 perennis
L. quercina subsp. + + + +
 quercina
L. quercina subsp. +
 wilhelmsiana
L. saligna + + + + + + + (c)
L. serriola f. +
 integrifolia
L. serriola f. + + + + + + +
 serriola
L. sibirica
L. tatarica subsp. + + + +
 tatarica
L. tenerrima + +
L. viminea subsp.
 alpestris
L. viminea subsp. +
 chondrilliflora
L. viminea subsp.
 ramosissima
L. viminea subsp. + + + + + +
 viminea
L. virosa + + + + (c)
L. watsoniana

 Country

Lactuca spp. DEU DNK ESP FIN FRA GBR GRC

L. acanthifolia +
L. altaica
L. aurea +
L. intricata +
L. livida +
L. longidentata
L. palmensis + (b)
L. perennis subsp. +
 granatensis
L. perentinis subsp. + + + + + +
 perennis
L. quercina subsp. + + +
 quercina
L. quercina subsp.
 wilhelmsiana
L. saligna + + + + +
L. serriola f. + + +
 integrifolia
L. serriola f. + + + + + + +
 serriola
L. sibirica +
L. tatarica subsp. + + +
 tatarica
L. tenerrima + +
L. viminea subsp. + (d)
 alpestris
L. viminea subsp. + +
 chondrilliflora
L. viminea subsp. + +
 ramosissima +
L. viminea subsp. + + + +
 viminea
L. virosa + + + + +
L. watsoniana

 Country

Lactuca spp. HRV HUN ITA LUX MKD NLD NOR

L. acanthifolia
L. altaica
L. aurea +
L. intricata
L. livida
L. longidentata + (a)
L. palmensis
L. perennis subsp.
 granatensis
L. perentinis subsp. + + + + + +
 perennis
L. quercina subsp. + + +
 quercina
L. quercina subsp.
 wilhelmsiana
L. saligna + + + + +
L. serriola f. + +
 integrifolia
L. serriola f. + + + + + + +
 serriola
L. sibirica +
L. tatarica subsp. + +
 tatarica
L. tenerrima +
L. viminea subsp.
 alpestris
L. viminea subsp. +
 chondrilliflora
L. viminea subsp. +
 ramosissima
L. viminea subsp. + + +
 viminea
L. virosa + (c) + (c) + + +
L. watsoniana

 Country

Lactuca spp. POL PRT ROM RUS

L. acanthifolia
L. altaica +
L. aurea +
L. intricata
L. livida
L. longidentata
L. palmensis
L. perennis subsp.
 granatensis
L. perentinis subsp. + + + +
 perennis
L. quercina subsp. + + +
 quercina
L. quercina subsp. + +
 wilhelmsiana
L. saligna + + + +
L. serriola f. +
 integrifolia
L. serriola f. + + + +
 serriola
L. sibirica +
L. tatarica subsp. + + +
 tatarica
L. tenerrima
L. viminea subsp.
 alpestris
L. viminea subsp. +
 chondrilliflora
L. viminea subsp.
 ramosissima
L. viminea subsp. + + +
 viminea
L. virosa + + + +
L. watsoniana + (e)

 Country

Lactuca spp. SVL SVN SWE YUG

L. acanthifolia
L. altaica
L. aurea +
L. intricata
L. livida
L. longidentata
L. palmensis
L. perennis subsp.
 granatensis
L. perentinis subsp. + + +
 perennis
L. quercina subsp. + + + +
 quercina
L. quercina subsp.
 wilhelmsiana
L. saligna + +
L. serriola f.
 integrifolia
L. serriola f. + + + +
 serriola
L. sibirica +
L. tatarica subsp. + +
 tatarica
L. tenerrima
L. viminea subsp.
 alpestris
L. viminea subsp. +
 chondrilliflora
L. viminea subsp.
 ramosissima
L. viminea subsp. + + +
 viminea
L. virosa + + + +
L. watsoniana

Sources: Klekovski de & de Farka-Vukotinovic, 1869; Lindman, 1926,
1964; Burchard, 1929; Christiansen, 1953; Van Ooststroom, 1956;
Savulescu, 1965; Soo, 1970; Garcke, 1972; Hess et al., 1972;
Pawlowski & Jasiewicz, 1972; Domac, 1973; Sjogren, 1973; Coutinho,
1974; Josifovic, 1975; Ferakova, 1976, 1977; Fournier, 1977; Van
Rompaey & Delvosalle, 1979; Barcelo, 1980; Strid, 1980; Charpin &
Casas, 1981; Lack, 1981; Pignatti, 1982; Guerra, 1983; Langhe et
al., 1983; Sliskovic, 1983; Martincic & Susnik, 1984; Rollan, 1985;
Hulten & Fries, 1986; Barguin & Voggenreiter, 1987; Sfikas, 1987;
Valdes et al., 1987; Cvelev, 1989; Dostal, 1989; Bramwell & Bramwell,
1990; Poldini, 1991; Strid & Kit Tan, 1991; Weeda et al., 1991;
Andreev et al., 1992; Velayos et al., 1992; Hohenester & Welss,
1993; Turland et al., 1993; Adler et al., 1994; Clement & Foster,
1994; Press & Short, 1994; Rothmaler et al., 1994; Viney, 1994;
Stace, 1997; Benkert et al., 1998; Hamet-Ahti et al., 1998;
Polatschek et al., 1999; Roodwell, 2000; Lebeda et al., 2001a;
Zajac, 2001.

(a) Endemic to Sardinia.

(b) Endemic to the Canary Islands.

(c) Occurrence not clear (e.g., missing species; not reported
in local flora but mentioned by other authors).

(d) Endemic to Crete.

(e) Endemic to the Azores.

Table III
Distribution of wild Lactuca spp. in Asian Countries.

Key: AFG = Afghanistan; ARM = Armenia; CHN = China; IND = India;
IRN = Iran; IRQ = Iraq; ISR = Israel; JPN = Japan; KAZ = Kazakhstan;
LBN = Lebanon; MNG = Mongolia; PAK = Pakistan; RUS = Asian part of the
former Soviet Union (recently the Russian Federation); SAU = Saudi
Arabia; SYR = Syrian Arab Republic; TUR = Turkey; + = present.

 Country

Lactuca spp. AFG ARM CHN IND IRN

L. acanthifolia
L. aculeata + +
L. altaica + + +
L. auriculata
L. azerbaijanica +
L. benthamii +
L. bracteata +
L. brunoniana
L. cooperi +
L. crambifolia
L. decipiens + +
L. dissecta + + +
L. dolichophylla + + +
L. formosana +
L. georgica + +
L. glauciifolia + +
L. graciliflora +
L. indica + +
L. inermis
L. intricata
L. kashmiriana +
L. laevigata
L. lahuensis +
L. lessertiana
L. orientalis + + +
L. persica
L. picridiformis
L. polyclada +
L. quercina subsp. quercina + +
L. quercina subsp. wilhemsiana + +
L. raddeana +
L. rapunculoides +
L. remotiflora +
L. rosularis +
L. runcinata +
L. saligna +
L. scarioloides + +
L. scoparia
L. serriola + + + + +
L. seticuspis
L. sibirica +
L. sikkimennis
L. sororia +
L. takhtadzhianii +
L. taraxacifolia
L. tatarica subsp. tatarica + + + + +
L. triangulata +
L. triquetra
L. undulata + + + +
L. viminea subsp. viminea + +
L. violifolia
L. wallichiana +

 Country

Lactuca spp. IRQ ISR JPN KAZ LBN

L. acanthifolia
L. aculeata + + +
L. altaica +
L. auriculata +
L. azerbaijanica
L. benthamii
L. bracteata
L. brunoniana
L. cooperi
L. crambifolia
L. decipiens
L. dissecta
L. dolichophylla
L. formosana
L. georgica
L. glauciifolia
L. graciliflora
L. indica +
L. inermis
L. intricata
L. kashmiriana
L. laevigata
L. lahuensis
L. lessertiana
L. orientalis + + (b) +
L. persica
L. picridiformis
L. polyclada
L. quercina subsp. quercina
L. quercina subsp. wilhemsiana
L. raddeana +
L. rapunculoides
L. remotiflora
L. rosularis
L. runcinata
L. saligna + + +
L. scarioloides +
L. scoparia
L. serriola + + + +
L. seticuspis +
L. sibirica + +
L. sikkimennis
L. sororia +
L. takhtadzhianii
L. taraxacifolia
L. tatarica subsp. tatarica + +
L. triangulata +
L. triquetra +
L. undulata + + (b) +
L. viminea subsp. viminea + + +
L. violifolia
L. wallichiana

 Country

Lactuca spp. MNG PAK RUS SAU SYR TUR

L. acanthifolia +
L. aculeata + +
L. altaica + + (a)
L. auriculata +
L. azerbaijanica
L. benthamii
L. bracteata
L. brunoniana +
L. cooperi
L. crambifolia +
L. decipiens +
L. dissecta + +
L. dolichophylla +
L. formosana
L. georgica +
L. glauciifolia +
L. graciliflora
L. indica +
L. inermis +
L. intricata +
L. kashmiriana
L. laevigata +
L. lahuensis
L. lessertiana +
L. orientalis + +
L. persica +
L. picridiformis +
L. polyclada
L. quercina subsp. quercina +
L. quercina subsp. wilhemsiana
L. raddeana +
L. rapunculoides +
L. remotiflora +
L. rosularis
L. runcinata
L. saligna + + +
L. scarioloides +
L. scoparia +
L. serriola + + + + +
L. seticuspis
L. sibirica + +
L. sikkimennis +
L. sororia
L. takhtadzhianii
L. taraxacifolia +
L. tatarica subsp. tatarica + + +
L. triangulata
L. triquetra
L. undulata + + + +
L. viminea subsp. viminea + + + +
L. violifolia +
L. wallichiana +

Sources: Grossgejm, 1949; Rechinger, 1959, 1964, 1977; Kirpicznikov,
1964; Ohwi, 1965; Pavlov, 1966; Nasir & Ali, 1972; Chalkuziev, 1974;
Jeffrey, 1975; Walker, 1976; Feinbrun-Dothan, 1978; Kitagawa, 1979;
Mouterde, 1983; Polunin & Stainton, 1984; Collenettee, 1985; Zohary,
1991; Hajra et al., 1995; Iwatsuki et al., 1995; Tachtadjan, 1995;
Krasnoborov, 1997; Ling & Shih, 1997.

(a) Reported by Jacobs (2001), not reported in available local floras.

Table IV
Distribution of wild Lactuca spp. in African countries.

Key: + = present.

 Region

 East North West Central South
 Africa Africa Africa Africa Africa
Lactuca spp. (a) (b) (c) (d) (e)

L. ambacensis + +
L. attenuata + +
L. calophylla + + +
L. capensis + + + +
L. cichorioides +
L. cubanguensis +
L. dregeana +
L. dumicola +
L. elgonensis +
L. glandulifera + + + +
L. homblei + +
L. imbricata + + +
L. indica +
L. inermis + +
L. intybacea +
L. lasiorhiza + + + +
L. longespicata + + +
L. mwinilungensis +
L. orientalis +
L. paradoxa + + +
L. petrensis + +
L. praecox + + +
L. praevia + +
L. remotiflora +
L. rhynchocarpa +
L. saligna +
L. schulzeana + + +
L. schweinfurthii + + + +
L. serriola + + +
L. setosa + + +
L. songeensis + +
L. stebbinsii +
L. stipulata +
L. taraxacifolia +
L. tenerrima +
L. tinctociliata + +
L. tuberosa +
L. tysonii +
L. ugandensis + +
L. undulata +
L. viminea +
L. virosa + +
L. zambeziaca + +

Sources: Harvey & Sander, 1894; Hutchinson & Dalziel, 1963;
Jeffrey, 1966; Cufodontis, 1972; Lopez & Jimenez, 1974;
Tackholm, 1974; Dethier, 1982; Jafri & El-Gadi, 1983; Pope,
1984; Galland, 1988; Arnold & de Wet, 1993; Hepper & Friis,
1994; Jeffrey & Beenthje, 2000; Kilian, 2001.

(a) East Africa: Ethiopia, Kenya, Socotra Island (Yemen),
Somalia, Sudan, Tanzania.

(b) North Africa: Algeria, Egypt, Libya, Morocco, Tunisia.

(c) West (tropical) Africa: Cote D'Ivoire, Ghana, Guinea,
Liberia, Mali, Mauritania, Niger, Senegal, Sierra Leone.

(d) Central Africa: Burundi, Cameroun, Central African
Republic, Chad, Congo, Gabon, Nigeria, Rwanda, Uganda.

(e) South Africa: Angola, Botswana, Madagascar, Malawi,
Mozambique, Namibia, Republic of South Africa, Zambia,
Zimbabwe.

Table V
Distribution of wild Lactuca spp. in the Americas.

Key: CAN = Canada; MEX = Mexico; USA = United States of America;
ARG = Argentina; BLZ = Belize; CUB = Cuba; GTM = Guatemala;
PER = Peru; VEN = Venezuela; + = present.

 North America Central and South America

Lactuca spp. CAN MEX USA ARG BLZ CUB GTM PER VEN

L. biennis + +
L. canadensis + +
L. floridana + +
L. graminifolia + + + +
L. hirsuta + +
L. intybacea + + + + + +
L. ludoviciana + +
L. saligna + + +
L. serriola + + +
L. tatarica subsp.
 pulchella + +
L. terrae-novae + +
L. virosa + +

Sources: Steyermark, 1963; Alain, 1964; Lasser, 1964; Hulten, 1968;
Nash, 1976; Nesssler, 1976; Strausbaugh & Core, 1978; Cronquist, 1980;
McGregor et al., 1986; Brako & Zarucchi, 1993; Hickman, 1993; Kartesz,
1994; Holmgren et al., 1998; Zuloaga & Morrone, 1999; Balick et al.,
2000.


VII. Acknowledgments

The comments of Dr. N. A. Harriman (University of Wisconsin, Oshkosh, Wisconsin) are acknowledged. The authors are obliged to the Institute of Botany, Academy of Sciences of the Czech Republic (Pruhonice u Prahy, Czech Republic), the Department of Plant Taxonomy (Wageningen University, Wageningen, the Netherlands), and Horticulture Research International (Wellesbourne, UK) for generous providing library facilities. This work was supported by EU project GENE-MINE (Fifth Framework Programme of European Union, Contract no. QLK5-CT-2000-00722) "Improved use of germplasm collections with the aid of novel methodologies for integration, analysis and preservation of genetic data sets" and partly supported by project MSM 153100010 and the OECD Co-operative Research Programme "Biological Resource Management for Sustainable Agricultural Systems."

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