Effects of exotic pastures on tadpole assemblages in Pantanal floodplains: assessing changes in species composition

Land use change has been identified as a major driver of amphibian decline around the world. Yet we generally lack an understanding of how conversion to exotic pastures affects freshwater communities. This study examined tadpole assemblages in areas converted to exotic pastures and native wooded grasslands in northern Pantanal wetland, Midwestern Brazil. We tested the differences in site occupancy probability and assemblage composition during a flood season. We registered thirteen tadpole species, but only five were detected at levels suitable for occupancy modelling. For most species, tadpole occupancy was higher at the beginning of the flood season. Only <i>Scinax fuscomarginatus </i>occupancy was related with vegetation cover. Occupancy probability for three species (<i>Dendropsophus nanus</i>, <i>Physalaemus centralis</i>, and <i>Physalaemus cuvieri</i>) was associated positively with species richness of fish. Multivariate analyses demonstrated that exotic pastures hosted a different tadpole assemblage than native areas. The assemblage composition gradient was associated with species richness of fish, vegetation cover and volume of herbaceous vegetation and leaf litter. These differences likely relate to specific traits of individual anuran species (dietary plasticity, reproductive mode, and habitat preference). The study showed that some generalist species were able to cope with replacement of native vegetation by exotic species. However, management practices have maintained many areas in the Pantanal at a stage of a near-pristine wetland ecosystem and replacement of native vegetation by exotic pastures should be done with caution.