Diversification of the Neotropical avifauna: Disentangling the geographical patterns of persisting ancient taxa and phylogenetic expansions

With the development of digital distribution databases and comprehensive molecular phylogenies it is now possible to analyze diversification processes in time and space. This can be done by contrasting geographical distributions of sister groups up through the phylogenetic hierarchy, patterns of ancient clade diversity and species representing different ages. The “tropical niche conservatism” appears to be linked with the imbalance of the net sum of birth-death processes and the higher persistence of clades with low net speciation rates in the most productive tropical lowlands, compared with a higher turnover elsewhere. Divergent geographical distributions in groups that underwent phylogenetic expansion during the Neogene suggest a strong ability to access new ecoregions, notably in the south and in the tropical Andes region, where the most intensive speciation now takes place in the tree-line zone. It is suggested that specialization and dense niche packing forms the basis for continuous high speciation rates in the Andean “hotspot”.