Corridors increase ant diversity over time.

Abstract

Globally, habitat loss and fragmentation pose significant threats to biodiversity. Habitat corridors are often used in fragmented landscapes to reconnect isolated patches. However, understanding how corridors function can be challenging, as their effects may be confounded with simultaneous changes to habitat area, edge amount, and connectivity among patches. Here, we used a long-term, landscape scale experiment to investigate two potential mechanisms by which corridors may influence biodiversity-via increasing habitat connectivity or through increasing the amount of edge. With pitfall trap sampling conducted over 5 years (9-15 years since site establishment), we assessed the relative effects of connectivity and edge effects by measuring ant biodiversity in four ways: (1) taxonomic diversity, (2) functional diversity, (3) community composition, and (4) site-to-site variance in community composition (i.e., beta diversity). We found evidence of both connectivity and edge effects on ant diversity and community composition. Taxonomic diversity increased linearly in all patch types over time, yet accumulated more quickly in connected than in isolated patches. The faster accumulation of taxonomic diversity in connected patches was associated with greater site-to-site variance in community composition. Although we found no differences in mean taxonomic diversity within patches (alpha diversity), the faster accumulation of taxonomic diversity and greater beta diversity among patches with corridors suggests that ant diversity in connected patches may eventually surpass that of isolated patch types. Finally, while we found no effect of edge amount for how fast taxonomic diversity accumulated over time, functional group diversity accumulated more quickly in winged patches that have more edge habitat relative to interior habitat than rectangular patches. Taken together, these results add to a body of literature that shows the potential for habitat corridors to have positive effects on biodiversity by increasing connectivity and that these effects may continue to accrue over time.