One of the main objectives in ecology is the search of global patterns and the factors responsible for them. Understanding the ecological and evolutionary processes that underlie the geographical patterns requires an explicit consideration of the geographic ranges of taxa. Therefore, to explain these patterns we need to know how geographic ranges are structured. The main traits explored in this context correspond to single-taxon characteristics such as abundance and genetic variation. In this study we introduce a richness approach to study the internal structure of geographic ranges, based on analyzing the richness variation within a taxon’s range. A focal taxon may form different geographical associations in different parts of its range. Furthermore, these associations may look different depending on the relatedness and/or ecological interactions of the taxa considered. Considering taxa with different levels of relatedness and ecological similarity may inform about the causes of geographical richness patterns. More closely related taxa are thought to be strong potential competitors that could restrict the distribution of taxa. We used a geographic database of the bat family Phillostomidae (leaf-nosed bats) which is exclusive of the west hemisphere. We analyzed richness variation for phylogenetically nested sets of taxa (e.g. species within a genus, genus within a subfamily) and compare the patterns between sister pairs of taxa and equal range size taxa as well.
Results/Conclusions

Preliminary results show that most leaf-nosed bats shared their ranges with many other bats, irrespective of phylogenetic relationships or ecological similarity. This seems to be true for different levels of the taxonomic hierarchy (e.g. species and genus). Then, for this family of bats, the ecological interactions seem to be weak determinants of geographic richness patterns. These results support an important role for regional/historical factors (e.g. speciation) in the structure of geographic ranges.