Contrasting edge and pasture matrix effects on ant diversity from fragmented landscapes across multiple spatial scales

Abstract

Harmful effects of habitat loss and fragmentation can be detected across multiple spatial scales, yet most studies that aim to characterize these effects take place at a single spatial scale. Here we investigated responses in ant diversity to forest fragmentation across three spatial scales. We sampled ant diversity in a fragmented landscape in southeastern Brazil. We set transects with 15 pitfall traps (local scale response) within 16 forest fragments (fragment scale response) distributed in eight paired fragments separated by roads (mesoscale response). We measured habitat features at local, fragment and mesoscales and across the landscape. For each spatial scale, we then assessed the effects of ecological drivers measured at the same and subsequent higher spatial scales. Local diversity was higher with closer proximity to the matrix, and in fragments with high vegetation density. Both fragment species richness and β-diversity were higher in less circular fragments. However, at the mesoscale (pairs of fragments), total species richness decreased with increasing pasture matrix in the landscape (landscape driver). Edge and matrix effects lead to increased ant species richness at small spatial scales (due to an increase in generalist ants). However, when analyzed at a higher spatial scale, the responses to these effects were in fact reversed, leading to a decrease in ant diversity. Thus, we suggest that conservation efforts should take a multi-scale perspective (from local to landscape) and aim to protect both local and fragment characteristics that can buffer edge effects, as well as improve matrix quality in the landscape.