Abstract
The increase in species diversity from the Poles to the Equator is a major biogeographic pattern, but the mechanisms underlying it remain obscure. Our aim is to contribute to their clarification by describing the latitudinal gradients in species richness and in evolutionary age of species of New World bats, and testing if those patterns may be explained by the niche conservatism hypothesis. Maps of species ranges were used to estimate species richness in a 100 x 100 km grid. Root distances in a molecular phylogeny were used as a proxy for the age of species, and the mean root distance of the species in each cell of the grid was estimated. Generalised additive models were used to relate latitude with both species richness and mean root distance. This was done for each of the three most specious bat families and for all Chiroptera combined. Species richness increases towards the Equator in the whole of the Chiroptera and in the Phyllostomidae and Molossidae, families that radiated in the tropics, but the opposite trend is observed in the Vespertilionidae, which has a presumed temperate origin. In the whole of the Chiroptera, and in the three main families, there were more basal species in the higher latitudes, and more derived species in tropical areas. In general, our results were not consistent with the predictions of niche conservatism. Tropical niche conservatism seems to keep bat clades of tropical origin from colonizing temperate zones, as they lack adaptations to survive cold winters, such as the capacity to hibernate. However, the lower diversity of Vespertilionidae in the Neotropics is better explained by competition with a diverse pre-existing community of bats than by niche conservatism.
Highlights
The dramatic increase in species diversity from the Poles to the Equator is one of the most obvious biogeographic patterns, but the mechanisms underlying it remain quite obscure
Species richness is greater in tropical regions and more evolutionary basal species are found in higher latitudes
The predictions of niche conservatism related to the latitudinal distribution of derived and basal clades were not supported by our results, but this does not entirely rule out a role of niche conservatism to explain latitudinal richness trends in New World bats
Summary
The dramatic increase in species diversity from the Poles to the Equator is one of the most obvious biogeographic patterns, but the mechanisms underlying it remain quite obscure. It has been hypothesised that niche conservatism is important to explain how ecology and climate act on evolutionary and biogeographic processes (e.g. speciation, dispersal, extinction, invasions) to determine large scale patterns of species richness [3,4,5,6] This hypothesis is based on evidence that most of the components of the fundamental niche, which describes the set of abiotic conditions in which a species is able to persist [sensu 7], are conserved over long evolutionary time scales. Such conservatism may constrain the present geographic range of species [2,4], and influence latitudinal biogeographic patterns
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
