Diversity and Abundance of Ants at Forest Edges in the Great Smoky Mountains National Park

Paysen, Eric

Fragmented habitats are a common result of human activities that involve the clearing of native vegetation for various land uses. Habitat fragmentation has two primary and inseparable components: habitat loss and insularization. Landscape-level connectivity in fragmented habitats is diminished for many species, and edge characteristics become more important as the edge-to-interior ratio increases. The study of the effects of edges on biodiversity has compelled ecologists to study them for over a century and has influenced the design and management of natural preserves. Invasion of habitats by non-native species is a phenomenon that coincides with the increased human activity typical of fragmented habitats. Biological invasions are second only to habitat loss in terms of effects on native biota and synergistically compound the impacts of habitat fragmentation. The primary goal of this research was to describe the effects of habitat boundaries between undisturbed forests and artificially maintained grasslands on ant communities. A secondary goal was to ecologically assess the invasive potential of Pachycondyla chinensis (Emery), a little-studied adventive species in North America. Ant communities were sampled across the forest-grassland habitat boundary in the Great Smoky Mountains National Park (GSMNP), North Carolina and Tennessee, USA. Different ant communities were found on either side of this boundary. The native forest-ant community is intact within 15 m of edge zones. Twenty-seven significant indicator species were identified within four distinct ant assemblages. Ecotonal effects were observed only in forests when individual species abundance was compared at different distances into undisturbed forest habitat. Analysis of variance revealed differential abundance, with respect to habitat boundaries, of significant indicator species in both grassland and forest habitats. Differences in rarely collected species as visualized with rank abundance plots, occurred in the forest only. Total species richness was greatest near edge zones in both forest and grassland habitats. However, within-habitat ecotonal effects were not found in analysis of averaged, per sample species richness or diversity across distances from edges. Analysis of averaged per sample ant abundance revealed an ecotonal effect in the grassland where values increased with distance from the forest edge. Several biotic and abiotic habitat characteristics were identified that correspond with patterns in habitats and ant distributions. These characteristics have not been causally linked with trends in ant communities and should be interpreted as starting points for future hypothesis testing. Pachycondyla chinensis (Emery), native to southeastern Asia, was detected in the United States more than 70 years ago. Basic knowledge regarding the biology and ecology of this species is lacking, especially in its expanded range in North America. This work documents the first collection of P. chinensis within the forests of GSMNP. In South Carolina, USA, habitats were surveyed, colonies were excavated, and ant communities were sampled along transects to determine the nest characteristics and formicid-community ecology of P. chinensis....

Diversity and Abundance of Ants at Forest Edges in the Great Smoky Mountains National Park

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