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Comparative analysis of plant and ground dwelling arthropod communities in lacustrine dune areas with and without Centaurea biebersteinii (Asteraceae).

INTRODUCTION

Exotic species introductions can alter many ecological processes, including dune succession, which depend on native plant species and local successional patterns (Walker and Vitousek, 1991; Leege and Murphy, 2001). Although sand dunes stabilize naturally as a result of native plant succession, rapid stabilization initiated by exotic species invasions can exclude organisms adapted to the movement of sand in highly dynamic portions of dunes (Garcia-Mora et al., 2000). Sand dune systems are especially vulnerable to exotic species invasion because of limited competition by native plants due to low amounts of plant cover and frequent, high intensity disturbances (Crawley, 1987). In other systems, higher levels of native biodiversity may exclude exotic species invasion, but dynamic systems like sand dunes, which repeatedly return to early successional stages, tend to have inherently lower diversity levels (Morrison and Yarranton, 1973; Kennedy et al., 2002).

Dynamics of coastal sand dune systems direct the potential success of establishing organisms. This allows specialized communities to form, composed of organisms adapted to exploit limited resources and survive periodic burial by sand (Carter, 1991; Mann, 1998; Mann and Perumal, 1999; Bach, 2001). Over time, as succession occurs, portions of a sand dune become more stable (Cowles, 1899; Olson, 1958; Johnson, 1997; Lichter, 1998). The retention of sand by pioneering plant species allows organisms that are less adapted to burial and excavation by sand movement to colonize these areas (Moreno-Casasola, 1986; Bach, 2001). With this rapid immigration, increases in species diversity can be expected as the surface of a dune is stabilized, over several hundreds of years. Through competition and other successional processes, herbaceous sand dune plant community diversity will subsequently plateau and decrease over time (Morrison and Yarranton, 1973).

Spotted knapweed, Centaurea biebersteinii de Candolle (Asteraceae) (syn C. maculosa de la Marck), is an exotic plant that has destructively invaded millions of hectares across most of the United States and Canada (Watson and Renney, 1974; Story, 2002). Since its introduction to British Columbia, Canada, in the late 1800s (Harris and Cranston, 1979), spotted knapweed has invaded rangelands, roadsides and other disturbed areas in all of the contiguous United States, Alaska, Hawaii and all Canadian provinces except the Northwest Territories and Nunavut. Its effects in rangelands include increased soil runoff and sedimentation, reduced plant biodiversity and decreased wild and domestic grazer production (Lacey et al., 1989; Kedzie-Webb et al., 2001; Olson and Wallander, 2001). Spotted knapweed is labeled as one of the most destructive invasive plants in North America because of the latter effect (Harris and Cranston, 1979).

Lacustrine sand dune systems provide suitable habitat for spotted knapweed due to factors such as high levels of disturbance, drier sandy soils and high winds for dispersal (Watson and Renney, 1974). Spotted knapweed produces seeds with three different germination requirements: dark germinating, light-sensitive dormant and light-insensitive dormant seeds (Nolan and Upadhyaya, 1988). Sand accretion around the parent plant may increase the success of the dark germinating seeds. Persistence of spotted knapweed seeds in the soil, which can reach 7 y, can also greatly increase population numbers when environmental factors become suitable (Davis et al., 1993).

An extensive survey of the plants of Pictured Rocks National Lakeshore, Michigan, was carried out in 1973. At that time, spotted knapweed was not represented within the Grand Sable Dunes, but was limited to roadsides within Pictured Rocks National Lakeshore (Read, 1975). A plant community survey, focusing on the Grand Sable Dunes, was performed in 1975. This survey recorded spotted knapweed within the dunes, but it was not a major component of any plant communities (Bach, 1978). Spotted knapweed has expanded its cover to over 30 ha within the 918 ha Grand Sable Dunes since the late 1970s (National Park Service, unpublished data).

Along with the specialized plant communities that develop within a dune system, ground dwelling arthropods are sensitive to alterations to the surrounding environment (Eyre and Rushton, 1989). This sensitivity has resulted in the use of ground dwelling arthropods as measures of ecosystem biodiversity (Ricci et al., 1998; Barrows, 2000; Niemela et al., 2000; Perner, 2003). Since ground dwelling arthropod communities are closely associated with surrounding plant communities, changes in plant diversity often alter the distribution of arthropods (Southwood et al., 1979).

The objectives of this study were to: (1) characterize differences in native and exotic plant communities in areas with and without spotted knapweed in Grand Sable Dunes; and (2) characterize ground dwelling arthropod communities associated with spotted knapweed infested and non-infested areas within a dune environment. Understanding differences in native plant and insect communities within the Grand Sable Dunes in areas with and without spotted knapweed will assist land managers in restoration efforts by providing information regarding the relative impacts of spotted knapweed.

METHODS

STUDY AREA AND TRANSECTS

Study sites were located in the Grand Sable Dunes of Pictured Rocks National Lakeshore (46[degrees]39'38"N, 86[degrees]1'54"W) in the Upper Peninsula of Michigan along Lake Superior. Spotted knapweed and other major plant cover types were mapped within the Grand Sable Dunes during the summer of 2000 (National Park Service, unpublished data). The majority of the Grand Sable Dunes are herbaceous plant communities, however patches of Jack Pine and Northern Hardwood forest types do exist. These forest patches provide limited dune stabilization.

The three largest patches of spotted knapweed (10.7, 6.3, 4.8 ha) were selected for these studies as they each provided sufficient area for both plant and arthropod surveys. Transects located where spotted knapweed was not found were mapped through portions of the dunes with visually comparable sand activity levels. Transects were not located in the highly active, successionally younger areas of the foredune complex since these areas have been identified as having lower overall plant species diversity due to the inability of some species to survive high levels of sand accretion (Maun, 1998). This reduction in plant diversity could, in turn, directly affect insect collections (Crisp et al., 1998; Haddad et al., 2001; Leege and Murphy, 2001). The areas of spotted knapweed used in this study have been present within the Grand Sable Dunes for a minimum of five years (National Park Service, unpublished data), allowing initially higher levels of plant diversity to normalize for areas with long-term spotted knapweed infestation.

Spotted knapweed transects were 500-600 m long and mapped on the long axis of each of the three largest patches of knapweed within the Grand Sable Dunes. Three non-spotted knapweed areas were selected within dune plant communities in proximity to patches of spotted knapweed areas and each had a 500 m long transect located along its longest axis. The northern end of one transect in one non-spotted knapweed area did traverse a small patch of knapweed. For the purposes of analysis, each transect was regarded as a treatment, and samples of data collected along each transect were viewed as replicates.

Due to the inherent problems of pseudoreplication in this type of design, precautions were taken to randomize the placement of vegetation quadrats and pitfall traps along transects within the logistical constraints of working within the dune system. In most analyses, contrasts were made to compare the three knapweed transects with the three non-knapweed transects.

PLANT SURVEY

Transects were divided into 20 m segments and a 1 [m.sup.2] quadrat was randomly located along the transect line within each 20 m segment. All plants within each quadrat were identified to species, except Carex and Poaceae species, and ocular percent cover for each was estimated to the nearest 5%. Percent cover values estimated as <5% was coded as 2% for statistical comparisons.

Total species richness, diversity and evenness were calculated for each quadrat. Species richness (S) was the total number of species rooted within the quadrats. Shannon-Weaver Diversity Index (H) was calculated as

H = - [summation] [p.sub.i] ln(pi)

where [p.sub.i] = area covered by a species/total meters covered by all species (Shannon and Weaver, 1949; Hayek and Buzas, 1997). The value of H is the entropy, or disorder, of a discrete set of probabilities (Shannon and Weaver, 1949). This suggests that larger values of H result from samples that are more diverse, meaning there is a lower probability of encountering a specific species within the sample area. Species evenness (E) was calculated as

E = ([e.sup.H])/S

where S = species richness, H = species diversity and e = the base of natural logarithm (Hayek and Buzas, 1997).

Richness and diversity were also calculated separately for native plants and for exotic plants, excluding spotted knapweed. Plants were identified as native or exotic according to USDA PLANTS Database (2003). Spotted knapweed was excluded from the exotic plant species analysis. A nested analysis of variance (ANOVA) was used to test for differences in species richness and diversity between areas with and without spotted knapweed for all plant species, native plant species and exotic plant species, as well as evenness for all plant species. Included in the nested ANOVA were areas with and without spotted knapweed and transects within these two treatments. A t-test was used to test for differences in percent bare sand cover between areas with and without spotted knapweed.

Frequency of occurrence, the number of quadrats where each species was encountered, was calculated for each plant species. The five plant species with the highest overall frequency in the spotted knapweed areas, and the five plant species with the highest overall frequency in the non-spotted knapweed areas, were used to test the independence of the occurrence for each of these species and the presence of spotted knapweed using G-tests (Sokal and Rohlf, 1998).

ARTHROPOD TRAPPING

Ground dwelling arthropods were sampled along each transect using pitfall traps. Traps were composed of two plastic drinking cups (8.5 cm diameter, 12.5 cm height), one inside the other, buried with the lip of the inner cup level with the ground surface. Traps were covered with a Styrofoam plate (18 cm diameter) supported on four 9 cm nails to exclude rain. In each trap, approximately 75 ml of 50% propylene glycol (Prestone LowTox[R] Antifreeze) was used as a killing agent and preservative. Traps were placed along the six transects within spotted knapweed and non-spotted knapweed areas. Ten traps were placed in two groups of five along each transect. Trap groups were located approximately 80-100 m from the end of each transect, 400-500 m from the other trap group on the same transect, and were considered statistically independent. Within each group of five, traps were placed 5 m apart along the transect to optimize trapping efficiency as described by Ward et al. (2001).

Traps were emptied after one week. After emptying, the plate was closed to ground level. Traps were left closed for three weeks at which time the traps were reopened for the next 1-wk trapping cycle and new propylene glycol was added. Traps were closed for 3 wk to allow recolonization of the areas by arthropods and reduce the likelihood of population depression due to trapping. A total of five trapping cycles were carried out from 9 May 2003 to 28 Aug. 2003.

Trap catches were sorted to family and pooled for each trap group, except for the order Araneae. The abundances of ground dwelling arthropods in taxa that occurred in at least 20% of traps were each used for single taxon analyses. In addition, the abundance of Trimerotropis huroniana Walker (Orthoptera: Acrididae), a state threatened locust species, was also used in analysis.

Trap captures were pooled over the trapping cycles within each trap group. Differences in arthropod abundances between areas with and without spotted knapweed were identified using a nested ANOVA. Data were transformed where needed in order to meet assumptions of normality.

RESULTS

PLANT SURVEY

A total of 27 plant species were identified along the six transects within the Grand Sable Dunes, Pictured Rocks National Lakeshore, with 85 quadrats along spotted knapweed transects and 75 quadrats along non-spotted knapweed transects. Of the plants encountered, 22 were native and five were exotic, including spotted knapweed (Table 1). In areas with spotted knapweed, cover by bare sand was significantly less (51%) compared to areas without spotted knapweed (61%) ([t.sub.(1),158] = 2.4, P = 0.009).

Total plant species richness was significantly greater for spotted knapweed quadrats than for non-spotted knapweed transects ([F.sub.1.154] = 5.15, P = 0.025) (Fig. 1). Total species diversity ([F.sub.1,154] = 1.95, P > 0.05) and total species evenness [F.sub.1,154] = 1.25, P > 0.05) did not differ significantly between spotted knapweed and non-spotted knapweed quadrats (Fig. 1). Native richness ([F.sub.1,154] = 7.85, P = 0.005) and diversity ([F.sub.1,154] = 11.76, P < 0.001) were significantly greater in non-spotted knapweed quadrats than in spotted knapweed quadrats (Fig. 1). Exotic richness ([F.sub.1,154] = 14.83, P < 0.001) and diversity ([F.sub.1,154] = 4.66, P = 0.032) were significantly greater in spotted knapweed quadrats than in non-spotted knapweed quadrats (Fig. 1).

The five plant taxa with the greatest total frequency along non-spotted knapweed transects were Artemisia campestris, Carex spp., Hieracium caespitosum, Lathyrus japonicus and Poaceae spp. For spotted knapweed transects, the five plant taxa with the highest frequency, excluding spotted knapweed, were Carex spp., Fragaria virginiana, H. caespitosum, Poaceae spp. and Rumex acetosella. Of the three taxa of high frequency along transects in both spotted knapweed and non-spotted knapweed areas, only H. caespitosum occurred in a greater percentage of quadrats along spotted knapweed transects, whereas Carex spp. and Poaceae spp. occurred in a greater percentage of quadrats along non-spotted knapweed transects. Fragaria virginiana and R. acetosella occurred in greater percentages of quadrats in areas of spotted knapweed than in non-spotted knapweed areas (Table 2).

ARTHROPOD TRAPPING

Thirty-two arthropod families were captured from two classes and nine orders (Table 3). Families captured in at least twenty percent of traps were Opiliones: Phalangiidae (harvestmen), Hymenoptera: Formicidae (ants), Coleoptera: Carabidae (ground beetles), Coleoptera: Staphylinidae (rove beetles), Coleoptera: Curculionidae (weevils), as well as the Arachnid order Araneae (spiders). These families also comprised the majority of individuals captured (Table 3).

Nested ANOVA for identifying differences in arthropod abundances between transects with and without spotted knapweed was used with the inclusion of all trapping cycles. Abundance data for Phalangiidae and Curculionidae required a square root transformation and Formicidae required a natural log transformation in order to meet assumptions of normality. Significantly more Curculionidae ([F.sub.1,53] = 4.54, P = 0.038) and Formicidae ([F.sub.1,53] = 4.92, P = 0.031) were trapped along transects with spotted knapweed than along nonspotted knapweed transects (Fig. 2). There was no significant difference in Araneae ([F.sub.1,53] = 0.11, P > 0.05), Carabidae ([F.sub.1,53] = 0.56, P > 0.05), Phalangiidae ([F.sub.1,53] = 0.48, P > 0.05), Staphylinidae ([F.sub.1,53] = 2.56, P > 0.05) and Trimerotropis huroniana ([F.sub.1,17] = 2.39, P > 0.05) abundances between areas with and without spotted knapweed (Fig. 2).

[FIGURE 1 OMITTED]

DISCUSSION

Plant diversity did not differ significantly between areas with and without spotted knapweed, suggesting that spotted knapweed does not have an adverse affect on the diversity of plant communities within the Grand Sable Dunes. However, the Shannon-Weaver's Diversity Index does not take into account which plant is which; a plant of high ecological importance receives the same weight as a plant with low importance. By separating native and exotic species our intent was to find how plant communities differed within spotted knapweed and non-spotted knapweed areas. Comparing native and exotic diversity indices within spotted knapweed and non-spotted knapweed areas indicated that spotted knapweed infested areas had a lower native diversity and a higher exotic diversity.

The differences measured in native plant diversity and exotic plant diversity may be a result of the sand dunes stabilizing at a more rapid rate than would naturally occur through succession. Within the Grand Sable Dunes, natural successional patterns include transitions from herbaceous dominance to Jack Pine forest and then to Northern Hardwood forest, similar to patterns observed in other northern lacustrine dune systems (Lichter, 1998). Sand movement within dune systems is one important factor that determines the distribution of plants (Moreno-Casasola, 1986). The increase in plant cover in areas with spotted knapweed resulted in a decrease in bare sand, possibly creating habitat for plants not adapted to shifting sand within the dunes. Increases in the invasion of exotic plants may increase competition, which also influences the distribution of plants within sand dunes (Studer-Ehrensberger et al., 1993).

Two of the five plant species with the highest frequency along spotted knapweed transects, excluding spotted knapweed, were exotic (Hieracium caespitosum and Rumex acetosella). Both of these species occurred at lower frequencies along non-spotted knapweed transects (Table 2). Also, four of the five native plant species occurring at high frequencies in areas with and without spotted knapweed were more frequent along transects in uninfested areas than in infested areas (Table 2). Within the Grand Sable Dunes, areas with greater native plant diversity contained fewer exotics. The greater incidence of exotic plants in areas with spotted knapweed may be due to the presence of spotted knapweed, but other environmental factors may influence the distribution of exotic species.

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

More individuals of Formicidae and Curculionidae were captured throughout the trapping period in areas of spotted knapweed. The increased abundance of Formicidae in areas with spotted knapweed strengthens the hypothesis that spotted knapweed has stabilized the Grand Sable Dunes at a more rapid rate than would occur through natural succession. While areas within the Grand Sable Dunes used for arthropod trapping were chosen for similar apparent stability, areas of native vegetation may have a more frequent disturbance rotation than areas with less native vegetation. Increased total plant richness in areas with spotted knapweed (Fig. 1) would provide increased foraging sites and prey locations for Formicidae, along with the increased dune stability, evidenced by the reduced amount of bare sand. Previous surveys of Formicidae nest locations in sand dunes suggest ant nest establishment is related to the proximity of vegetation and the stabilization of the dunes (Albuquerque et al., 2005).

Arthropod families such as Curculionidae may have been captured more in spotted knapweed areas due to the foraging behaviors of these herbivorous taxa. Pitfall trapping is a passive measurement technique that relies on the activity of ground dwelling arthropods. Curculionidae individuals may spend more time actively searching for host plants in the spotted knapweed areas, with higher exotic diversity, than in areas without spotted knapweed, with higher native diversity. Alternatively, Curculionidae activity in spotted knapweed areas may be stimulated by chemicals, such as cnicin, in spotted knapweed biomass. Cnicin can be lethal to arthropods that are not adapted to consume plant material that contains the chemical (Landau et al., 1994). Additional tests would be necessary to determine reasons for the observed differences in trap catch of this taxon between spotted knapweed and knapweed free areas.

The rarity of T. huroniana, the state threatened Lake Huron locust, may have contributed to the lack of significance in trap captures between areas with and without spotted knapweed. However, Trimerotropis huroniana was captured three times more frequently along non-spotted knapweed transects than spotted knapweed transects. Trimerotropis huroniana may be more dependent on the presence of native plant species, rather than the presence of an exotic plant species. Restricted to the open dunes of the Great Lakes, T. huroniana requires dune movement associated with high quality, natural dune systems (Ballard, 1989). It can decrease significantly in population size in dune systems with large numbers of invasive weeds (Rabe, 1999).

Active management to restore native plant diversity and native plant communities in the dunes may be appropriate to increase the population of Trimerotropis huroniana in the Grand Sable Dunes. This active management may also support natural plant and arthropod diversity within dune system communities. Loss of native plant diversity may be attributed to the increases in spotted knapweed invasion and its facilitation of other exotic plant species (Myers and Bazely, 2003). Appropriate management strategies to fit with National Park Service objectives would be hand pulling spotted knapweed plants prior to seed production, as well as classical biological control. The National Park Service has carried out spotted knapweed pulling programs, but available funding has limited the size and frequency of these operations. Effective biological control agents, like Agapeta zoegana (Lepidoptera: Cochylidae) and Cyphocleonus achates (Coleoptera: Curculionidae) that cause reductions in spotted knapweed biomass (Story et al., 2000, 2006) may also aid in the restoring of native plant diversity within the Grand Sable Dunes.

Acknowledgments.--Brian L. Beachy, Ryan D. DeSantis, Elizabeth E. Graham, Emily L Marshall and Justin N. Rosemier hiked miles in the Grand Sable Dunes assisting in trap collection and identifying plants. Bryan K. Roosien assisted with statistical analyses. Funding was provided by the Michigan Technological University Graduate School. Field studies were carried out under National Park Service Scientific Research and Collection Permit Study # PIRO-2002-SCI-0014.

SUBMITTED 7 JULY 2005

ACCEPTED 8 MARCH 2007

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JORDAN M. MARSHALL (1) AND ANDREW J. STORER

School of Forest Resources and Environmental Science, Michigan Technological University, Houghton 49931

AND

BRUCE LEUTSCHER

Pictured Rocks National Lakeshore, P.O. Box 40, Munising, Michigan 49862

(1) Corresponding author present address: Cooperative Emerald Ash Borer Project, 5936 Ford Ct. Suite 200, Brighton, Michigan 48116. Telephone: (810) 844-2701; FAX: (810) 844-0583; e-mail: jmmarsha@ mtu.edu
TABLE 1.--Family/species list of plants and total number of quadrat
occurrences (n = 85, with spotted knapweed; n = 75, without spotted
knapweed) (with mean percent cover [SE]) sampled Jun. 2003 in Grand
Sable Dunes, Pictured Rocks National Lakeshore, Michigan.
Note: Percent cover values recorded as <5% were coded as 2% for
statistical analysis

              Family
                                         Spotted         Non-Spotted
                                        Knapweed          Knapweed
          Genus species                  Patches           Patches

Aceraceae
  Acer rubrum Linnaeus                1 (2)
Asclepiadaceae
  Asclepias syriaca Linnaeus          6 (3.8 [6.1])
Asteraceae
  Achillea millefolium Linnaeus                         3 (7.3 [6.6])
  Artemisia campestris Linnaeus      12 (4.8 [4.3])    38 (4.1 [1.9])
  Centaurea biebersteinii de         58 (15.4 [2.0])
    Candolle
  Leucanthemum vulgare Lamarck        1 (2)
  Hieracium caespitosum Dumortier    53 (5.5 [2.1])    28 (3.6 [2.2])
  Tanacetum bipinnatum (Linnaeus)     9 (5.2 [5.0])     7 (17.9 [4.3])
    Schultz-Bip. subsp. Huronense
    (Nuttall) Breitung
Boraginaceae
  Lithospermum caroliniense           2 (3.5 [10.6])    3 (12.3 [6.6])
  (Walter) MacMillan
Caryophyllaceae
  Minuartia michauxii (Fenzl)         5 (2 [6.7])       5 (2 [5.1])
    Farwell var. michauxii
  Stellaria longipes Goldie           1 (10)
Cistaceae
  Hudsonia tomentosa Nuttall          7 (32.9 [5.7])
Cyperaceae
  Carex spp.                         33 (5.7 [2.6])    45 (10.3 [1.7])
Ericaceae
  Arctostaphylos uva-ursi             1 (2)             1 (40)
    (Linnaeus) Sprengel
Equisetaceae
  Equisetum hyemale Linnaeus          5 (4.8 [6.7])     2 (3.5 [8.1])
Fabaceae
  Lathyrus japonicus Willdenow        5 (5.2 [6.7])    39 (10.6 [1.8])
    var. maritimus (Linnaeus)
    Kartesz & Gandhi
Liliaceae
  Maianthemum canadense               2 (11 [10.6])
    Desfontaines
  Maianthemum stellatum              11 (11.5 [4.5])    5 (7.2 [5.1])
    (Linnaeus) Link
Pinaceae
  Pinus banksiana Lambert            14 (35.7 [4.0])    2 (38.5 [8.1])
Plantaginaceae
  Plantago lanceolata Linnaeus        5 (5.8 [6.7])     5 (3.2 [5.1])
Poaceae
  dominated by Ammophila             64 (21.9 [1.9])   68 (17.3 [1.4])
  breviligulata Fernald
Polygonaceae
  Rumex acetosella Linnaeus          27 (5.0 [2.71)    12 (3.4 [3.3])
Pyrolaceae
  Pyrola asarifolia Michaux           1 (10)
Rosaceae
  Fragaria virginiana Duchesne       29 (7.2 [2.8])    11 (5.8 [3.5])
  Rosa blanda Aiton                   3 (8.0 [8.7])     4 (10.5 [5.7])
Salicaceae
  Salix interior Rowlee               8 (13.5 [5.3])    4 (12.5 [5.7])
Scrophulariaceae
  Melampyrum lineare Desrousseaux     2 (3.5 [10.6])

              Family

          Genus species               Native/Exotic

Aceraceae
  Acer rubrum Linnaeus                   Native
Asclepiadaceae
  Asclepias syriaca Linnaeus             Native
Asteraceae
  Achillea millefolium Linnaeus          Native
  Artemisia campestris Linnaeus          Native
  Centaurea biebersteinii de             Exotic
    Candolle
  Leucanthemum vulgare Lamarck           Exotic
  Hieracium caespitosum Dumortier        Exotic
  Tanacetum bipinnatum (Linnaeus)        Native
    Schultz-Bip. subsp. Huronense
    (Nuttall) Breitung
Boraginaceae
  Lithospermum caroliniense              Native
  (Walter) MacMillan
Caryophyllaceae
  Minuartia michauxii (Fenzl)            Native
    Farwell var. michauxii
  Stellaria longipes Goldie              Native
Cistaceae
  Hudsonia tomentosa Nuttall             Native
Cyperaceae
  Carex spp.                             Native
Ericaceae
  Arctostaphylos uva-ursi                Native
    (Linnaeus) Sprengel
Equisetaceae
  Equisetum hyemale Linnaeus             Native
Fabaceae
  Lathyrus japonicus Willdenow           Native
    var. maritimus (Linnaeus)
    Kartesz & Gandhi
Liliaceae
  Maianthemum canadense                  Native
    Desfontaines
  Maianthemum stellatum                  Native
    (Linnaeus) Link
Pinaceae
  Pinus banksiana Lambert                Native
Plantaginaceae
  Plantago lanceolata Linnaeus           Exotic
Poaceae
  dominated by Ammophila                 Native
  breviligulata Fernald
Polygonaceae
  Rumex acetosella Linnaeus              Exotic
Pyrolaceae
  Pyrola asarifolia Michaux              Native
Rosaceae
  Fragaria virginiana Duchesne           Native
  Rosa blanda Aiton                      Native
Salicaceae
  Salix interior Rowlee                  Native
Scrophulariaceae
  Melampyrum lineare Desrousseaux        Native

TABLE 2.--Number of quadrats containing each of the five most frequent
species along transects in areas with and without spotted knapweed
within Grand Sable Dunes, Pictured Rocks National Lakeshore, Michigan.
Differences between areas with and without spotted knapweed are tested
using G tests. Significant differences marked with asterisk (*)

                            Occurrence of spotted
  Most frequent along       knapweed along transects
   transects in areas
 with spotted knapweed      present    absent          G         P

Carex spp.                    33         45           7.20    <0.01 *
Fragaria virginiana           29         11           8.31    <0.01 *
Hieracium caespitosum         53         28          10.08    <0.01 *
Poaceae spp.                  64         68           6.82    <0.01 *
Rumex acetosella              27         12           5.50    <0.05 *

                            Occurrence of spotted
  Most frequent along       knapweed along transects
   transects in areas
without spotted knapweed    present    absent          G         P

Artemisia campestris          12         38          25.58    <0.001 *
Carex spp.                    33         45           7.20    <0.01 *
Hieracium caespitosum         53         28          10.08    <0.01 *
Lathyrus japonicas             5         39          46.33    <0.001 *
Poaceae spp.                  64         68           6.82    <0.01 *

TABLE 3.--Total number of individuals captured of arthropod families
in areas with and without spotted knapweed May-Aug. 2003 in Grand
Sable Dunes, Pictured Rocks National Lakeshore, Michigan

Class

Order

Family                     05/09/2003         06/05/2003

Knapweed:               present   absent   present   absent

Insecta
  Coleoptera
    Anthicidae              93       59        32       14
    Carabidae                5       13         9
    Cerambycidae
    Chrysomelidae                               1
    Cicindelidae                      1                  4
    Coccinellidae            1
    Curculionidae           17        2         6        1
    Elatridae                3        1         1        3
    Meloidae                 1
    Pedilidae
    Scarabaeidae
    Silphidae
    Staphylinidae           10       18         9       51
    Tenebrionidae            3                 11
Insecta
  Homoptera
    Lygaeidae               19       15         7        3
    Nabidae                           1
    Scuteleridae
  Homoptera
    Cicadellidae
    Dictyopharidae
  Hymenoptera
    Chalcididae
    Encyrtidae
    Formicidae             305      171       679      264
    Scelinoidae
    Sphecidae                         1
    Tiphiidae
Insecta
  Lepidoptera
    Noctuidae
  Orthoptera
    Acrididae                                   2        2
    Gryllidae                6        4        86       29
    Mantidae
    Tettigoniidae
  Plecoptera
    Perlidae
Arachnidae
  Opiliones
    Phalangiidae                      2         2
  Araneae                   79       48        83      107

Class

Order

Family                     07/01/2003         07/30/2003

Knapweed:               present   absent   present   absent

Insecta
  Coleoptera
    Anthicidae              17        6        11       17
    Carabidae               10       17         1        2
    Cerambycidae                                         1
    Chrysomelidae            3
    Cicindelidae             1        3        10        3
    Coccinellidae
    Curculionidae           12        1                  2
    Elatridae
    Meloidae
    Pedilidae                         1
    Scarabaeidae             2       10
    Silphidae                        14
    Staphylinidae            1       56                  2
    Tenebrionidae
Insecta
  Homoptera
    Lygaeidae                                  55       11
    Nabidae
    Scuteleridae             1
  Homoptera
    Cicadellidae             1
    Dictyopharidae                                       1
  Hymenoptera
    Chalcididae              1
    Encyrtidae
    Formicidae            1797      975       461      369
    Scelinoidae                                          1
    Sphecidae                                            1
    Tiphiidae                                            1
Insecta
  Lepidoptera
    Noctuidae                         1                  1
  Orthoptera
    Acrididae                                   4        8
    Gryllidae                         1
    Mantidae
    Tettigoniidae            1                  1
  Plecoptera
    Perlidae
Arachnidae
  Opiliones
    Phalangiidae           161      254        90      164
  Araneae                   88      105        10        3

Class

Order

Family                     08/28/2003

Knapweed:               present   absent

Insecta
  Coleoptera
    Anthicidae              13       28
    Carabidae               19       24
    Cerambycidae             1
    Chrysomelidae
    Cicindelidae            22        5
    Coccinellidae
    Curculionidae            5        4
    Elatridae                         1
    Meloidae
    Pedilidae
    Scarabaeidae
    Silphidae                2
    Staphylinidae            1        3
    Tenebrionidae
Insecta
  Homoptera
    Lygaeidae                1
    Nabidae
    Scuteleridae
  Homoptera
    Cicadellidae
    Dictyopharidae
  Hymenoptera
    Chalcididae
    Encyrtidae
    Formicidae             252       87
    Scelinoidae                       1
    Sphecidae
    Tiphiidae
Insecta
  Lepidoptera
    Noctuidae
  Orthoptera
    Acrididae                         4
    Gryllidae
    Mantidae                 1
    Tettigoniidae
  Plecoptera
    Perlidae                          1
Arachnidae
  Opiliones
    Phalangiidae            91      119
  Araneae                   53       87
COPYRIGHT 2008 University of Notre Dame, Department of Biological Sciences
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Article Details
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Author:Marshall, Jordan M.; Storer, Andrew J.; Leutscher, Bruce
Publication:The American Midland Naturalist
Article Type:Report
Geographic Code:1USA
Date:Apr 1, 2008
Words:5756
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