Effect of structural connectivity on the assemblage diversity patterns of central Mexico icthyofauna

The complex hydrographic history of central Mexico can explain the phylogeographic patterns of endemic freshwater fish; nevertheless, the process that determines the assemblage patterns has been poorly studied. Here, we evaluated the freshwater fish diversity patterns of central Mexico through the estimation of α-diversity and taxonomic and phylogenetic β-diversity indices calculated from geographical distribution records and a time-calibrated phylogenetic tree. Furthermore, the effects of isolation by distance and isolation by climatic and hydrographic resistance on the turnover of species were evaluated at different temporal scales. The results suggested that the Chapala region was the most diverse area, with phylogenetic overdispersion. Geographical distance and climatic and hydrographic components played important roles in freshwater fish assemblage patterns within the region. Our findings demonstrated the relevance of the assessment of taxonomic and phylogenetic diversity, considering the temporal context of the landscape, in explaining patterns and suggesting conservation strategies. Because the variation in diversity was explained mainly by environmental gradients, conservation efforts would ideally protect enough sites to capture this entire gradient.