Metacommunity structure in a highly fragmented forest: has deforestation in the Atlantic Forest altered historic biogeographic patterns?

Abstract

AbstractAimTo determine whether there is evidence of changes in small mammals distributions and emergent metacommunity structure in the Atlantic Forest resulting from extensive habitat loss and fragmentation associated with anthropogenic activities.LocationSouth American Atlantic Forest from northeastern Brazil to eastern Paraguay.MethodsUsing presence–absence data for non‐volant small mammals, we analysed metacommunity structure for communities from 76 fragments distributed throughout Atlantic Forest. 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 Clementsian 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 Mantel tests evaluated correlations between them.ResultsRodent metacommunities had Clementsian structure, whereas marsupials had Gleasonian 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 conclusionsCompartment locations in Clementsian structures mirrored historical refugium locations and important vicariance events associated with large rivers. Despite extensive deforestation in Atlantic Forest, 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.