The Assembly of Communities in a Heterogeneous Landscape.

1. The Assembly of Communities in a Heterogeneous Landscape. • JoVonn G. Hill1,Keith S. Summerville2, Richard L. Brown1, and Joe A. MacGown1 • 1 Mississippi Entomological Museum, Department of Entomology and Plant Pathology, Box 9775, Mississippi State University, MS 39762. • Department of Environmental Science and Polic2 Department of Environmental Science and Policy, Drake University, Des Moines IA 50311-4505 • Results •  NMS and ANCOVA both revealed three distinct ant comunities (pasture, prairie, and "forests") between the four habitat types based on species composition and mean abundance per habitat type (Figures 3 and 4). •  Principal component analysis partitioned the 12 environmental variables into four axes with eigenvalues > 1 (Table 1). •  Axis 1 divides the sites into two types (open and forests), while Axis 2 separates pasture from prairie (Figure 5). •  Multiple regression models using the four significant principal components revealed that total species richness was significantly affected by variation in the first two PCA axes. Forested sites supported approximately nine more species of ants than prairie remnants, and 21 more than pastures (p=.0001) (Table 2). • Comparisons of functional group abundance between the four habitat types with multiple regressions are presented in Table 2 and Figures 6 and 7. • The removal of imported fire ants (Solenopsis spp.) from the Generalized Myrmiciniae functional group, revealed that the fire ants were most abundant in pastures with significantly lower numbers found in prairie remnants and the two forest types (df =3; F=42.31; p < .0001). Introduction Numerous species of ants have habitat preferences and respond quickly to disturbances to their environment; making them valuable for habitat monitoring. However, the effects of various environmental factors on ant communities remain uncertain (Wang et al. 2001 Env. Ent. 30: 439-448). This study investigates the relationship of ant community composition to various habitat characteristics by comparing ant communities and several environmental variables across four habitat types in the Black Belt Prairie and Flatwoods physiographic regions of Mississippi. The four habitat types include prairie, pasture, and upland forests in the Black Belt region and forests in the Flatwoods region (Figure 1). A. Cold Climate Specialists: 1. Stenamma meridionale Smith, 2. Prenolepis imparis (Say). B. Cryptic species: 3. Pyramica ornata (Mayr), 4. Hypoponera inexorata (Wheeler). C.Dominant Dolichoderinae: 5. Forelius mccooki (McCook), 6. Tapinoma sessile (Say). MethMethods Three sites were chosen for each of the four habitat types (Figure 2). At each site three circular plots, with a diameter of 25m each, were established. Six pitfall traps were run in each plot and checked twice a month from June to October 2003. Baits (tuna fish or shortbread cookie) were placed in each plot and all attracted ants were collected after 30 minutes. During this period all other foraging or nesting ants detected in each plot were hand collected. Baiting and hand collecting were done from June to October 2003 and from April to December 2004. Soil and litter samples (3.75 L per sample) were collected once a month from each forest plot in 2003 and twice a month in 2004, then placed in a Berlese funnels for 5-7 days for specimen extraction. All ant specimens were identified to species and assigned to one of six functional groups based on Andersen (1997. Jour. Biogeography 24: 433-460). D. Generalized Myrmicinae: 7. Solenopsis richteri Forel, 8. Crematogaster lineolata (Say). E. Opportunists: 9. Pheidole pilifera (Roger), 10. Polyergus lucidus longicornis Smith. F. Subordinate Camponotini: 11. Camponotus snellingi Bolton, 12. Camponotus mississippiensis Smith. • Conclusions • The two forests types (oak-hickory and Flatwoods) supported a different ant community and higher diversity than prairie or pasture habitats. No significant differences were found in species composition or abundance between the two forest types. • As a result of the effects of grazing and associated land management practices (as indicated by higher soil organic matter and less herbaceous diversity and height), ant diversity was significantly lowered in pastures, although the abundance of imported fire ants (Solenopsis spp.) was increased.. • Our analysis also indicated that environmental factors, such as the response of grassland flora to grazing or the effect of soil pH on development of the regional flora may have a more direct effect on the habitat template favored by ants than the presence of Solenopsisper se.