Metacommunity structure in a highly fragmented forest: has deforestation in the A tlantic F orest altered historic biogeographic patterns?

Aim To determine whether there is evidence of changes in small mammals distributions and emergent metacommunity structure in the A tlantic F orest resulting from extensive habitat loss and fragmentation associated with anthropogenic activities. Location South A merican A tlantic F orest from northeastern B razil to eastern P araguay. Methods Using presence–absence data for non‐volant small mammals, we analysed metacommunity structure for communities from 76 fragments distributed throughout A tlantic F orest. We evaluated coherence, range turnover and range boundary clumping for the entire non‐volant small mammal assemblage, marsupials, rodents and sigmodontine rodents separately. β‐diversity based on the multiplicative model was used to estimate the number of compartments (groups of sites with similar species composition) in C lementsian structures, and cluster analysis identified which sites formed compartments. Canonical correspondence analysis determined which environmental factors were associated with the gradients along which metacommunities were structured. Distance‐decay analysis evaluated the spatial structure in small mammal and environmental data, and M antel tests evaluated correlations between them. Results Rodent metacommunities had C lementsian structure, whereas marsupials had G leasonian structure. Compartment locations for rodents were consistent with areas of endemism. Temperature seasonality was most associated with the gradients along which metacommunities were structured. Assemblage and environmental dissimilarity among sites had significant positive relationships with geographic distance. Main conclusions Compartment locations in C lementsian structures mirrored historical refugium locations and important vicariance events associated with large rivers. Despite extensive deforestation in A tlantic F orest, small mammal distributions are consistent with expectations based on historical biogeography, suggesting that anthropogenic activities have not yet greatly affected geographic distributions of emergent metacommunity structures. However, extinction debt associated with recent fragmentation and habitat loss may exist. Any effective conservation plan for large and fragmented biomes must consider areas of endemism to maintain regional biodiversity and maintain sufficiently large and connected fragments to facilitate rescue effects and minimize effects of extinction debt.