PS 31-17
Drivers of amphibian's phylogenetic beta diversity components in the Brazilian Atlantic Forest
The concept of phylogenetic beta diversity (defined as the amount of unshared phylogenetic history between communities; hereafter PBD), has provided revealing insights into the evolutionary mechanisms that structure communities. In order to test the relative roles of current environmental conditions, geographic isolation and historical climatic stability, we investigated the spatial distribution of PBD of amphibians in the Brazilian Atlantic Forest, a forest biome where humid forests retracted during the cooler drier period of the Quaternary climate oscillations without being covered by ice. To assess phylogenetic dissimilarity among sites, we constructed a cladogram based on the time-calibrated tree. We used the UniFrac index to quantify PDB. Then, we decomposed UniFrac into a first component measuring ‘true’ phylogenetic turnover (the relative amount of gain and loss of unique lineages between communities) and phylogenetic diversity gradients (the amount of phylobetadiversity caused by differences in phylogenetic diversity between phylogenetically nested communities). The relative importance of current environmental variables, geographical distance and historic climatic stability in explaining the variation in PBD components was examined using a variance partitioning technique in which the total percentage of explained variation is partitioned into unique and common contributions of the sets of predictors.
Results/Conclusions
Our results show that the PBD of amphibians in the Brazilian Atlantic Forest is largely determined by lineage turnover. Independently, current environmental variables, geographical distance and historical climatic stability explained a similar proportion of the variation of the turnover component. Proportion of variation shared between current environmental variables and geographical distance and variation shared between these two variables with historical climatic stability explained on average 25% and 21% respectively of the turnover component. On the other hand, phylogenetic diversity component of PBD was not explained by the variables used in this study. The turnover component of PBD between sites from the stable region was, on average, 0.16 higher than between sites within the unstable region. These results are consistent with previous studies showing that patterns of species distribution are influenced by different processes depending on the regional species pool and scale considered. This study reveals that, even within the same biome, geographical distance (limited dispersal), historical events and current climatic processes are complementary predictors of PDB.