RESUMO
Evolutionary rate explanations for latitudinal diversity gradients predict faster speciation and diversification rates in richer, older and more stable tropical regions (climatic stability hypothesis). Numerous modern lineages have emerged in high latitudes, however, suggesting that climatic oscillations can drive population divergence, at least among extratropical species (glacial refugia hypothesis). This conflicting evidence suggests that geographical patterns of evolutionary rates are more complicated than previously thought. Here, we reconstructed the complex evolutionary dynamics of a comprehensive data set of modern mammals, both terrestrial and marine. We performed global and regional regression analyses to investigate how climatic instability could have indirectly influenced contemporary diversity gradients through its effects on evolutionary rates. In particular, we explored global and regional patterns of the relationships between species richness and assemblage-level evolutionary rates and between evolutionary rates and climatic instability. We found an inverse relationship between evolutionary rates and species richness, especially in the terrestrial domain. Additionally, climatic instability was strongly associated with the highest evolutionary rates at high terrestrial latitudes, supporting the glacial refugia hypothesis there. At low latitudes, evolutionary rates were unrelated to climatic stability. The inverse relationship between evolutionary rates and the modern latitudinal diversity gradient casts doubt on the idea that higher evolutionary rates in the tropics underlie the current diversity patterns of modern mammals. Alternatively, the longer time spans for diversity to accumulate in the older and more stable tropics (and not high diversification rates) may explain the latitudinal diversity gradient.
Assuntos
Biodiversidade , Mudança Climática , Especiação Genética , Mamíferos/genética , Animais , Camada de Gelo , Filogenia , Clima TropicalRESUMO
Historically, studies aimed at prospecting and analyzing paleontological and neontological data to investigate species distribution have developed separately. Research at the interface between paleontology and biogeography has shown a unidirectional bias, mostly focusing on how paleontological information can aid biogeography to understand species distribution through time. However, the modern suit of techniques of ecological biogeography, particularly species distribution models (SDM), can be instrumental for paleontologists as well, improving the biogeography-paleontology interchange. In this study, we explore how to use paleoclimatic data and SDMs to support paleontological investigation regarding reduction of taxonomic uncertainty. Employing current data from two neotropical species (Lagostomus maximus and Myocastor coipus), we implemented SDMs and performed model validation comparing hindcasts with dated fossil occurrences (~14k and ~20k years back present, respectively). Finally, we employed the hindcasting process for two South American fossil records of a misidentified species of caiman (Caiman sp.) to show that C. latirostris is the most likely species identity of these fossils (among four candidate species: C. latirostris, C. yacare, C. crocodilus, and Melanosuchus niger). Possible limitations of the approach are discussed. With this strategy, we have shown that current developments in biogeography research can favour paleontology, extending the (biased) current interchange between these two scientific disciplines.