Disentangling the multiple drivers of tadpole metacommunity structure in different ecoregions and multiple spatial scales

We evaluated the relative importance of environmental and spatial variables in structuring tadpole metacommunities at three hierarchical spatial scales in two ecoregions of the Atlantic Forest. Tadpole communities were generally more spatially structured at larger spatial scales. Environmental filtering processes seemed to be equally important at both large and small scales, however, spatially structured environmental variables were more important at larger scales, whereas non-spatially structured ones were more important at smaller scales. The importance of local environmental filters was also greater in the ecoregion that exhibits harsher environmental conditions, such as higher intensity of land-use patterns and dryer climate. This may indicate a greater role for stochastic assembly processes in more benign environments. Species co-occurrence patterns at the larger spatial scale mostly indicated biogeographical differences between the two ecoregions in a Clementsian structure, exhibiting two clear groups of species composition. Co-occurrence patterns at the smallest spatial scale were coherent only when strong environment gradients such as canopy cover were present. However, at the intermediate spatial scale the metacommunities became consistently non-coherent suggesting that species may be responding to processes acting at different spatial scales.