Comparative analysis of plant and ground dwelling arthropod communities in lacustrine dune areas with and without Centaurea biebersteinii (Asteraceae).
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.
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.
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).
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.
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).
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]
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
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
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|Author:||Marshall, Jordan M.; Storer, Andrew J.; Leutscher, Bruce|
|Publication:||The American Midland Naturalist|
|Date:||Apr 1, 2008|
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