Correlates of speciation and extinction rates in the carnivora.

摘要

Despite great research interest in macroevolutionary patterns in mammals, the factors causing differences in diversity among carnivoran lineages remain unclear. The objective of this study is to analyze whether differences in body size, degree of trophic specialization, and sociality level among carnivoran lineages are associated with differences in speciation and/or extinction rates during their recent evolutionary history (Miocene to Recent). I control for the effects of phylogenetic non-independence and use data on the diversity of both fossil and extant taxa to estimate evolutionary rates. To account for differences in fossil preservation, I explore taphonomic bias related to differences in body size and habitat breadth in carnivoran species based on the end-Rancholabrean record of carnivoran. The results of this analysis show a significant, positive relationship between body size and frequency of fossil specimens in non-cave deposits. Results indicate also that species richness of extant, small carnivorans is more underrepresented than that of larger carnivorans, especially in the end-Rancholabrean fossil record derived from non-cave localities. I also explore the usefulness of the known fossil record for assessing the accuracy of conflicting sister taxa hypotheses, and for identifying and accounting for confounding characters. The approach I propose is based on the comparison of temporal gaps among conflicting, well supported sister taxa hypothesis derived from the independent analysis of multiple data sets. The implementation of this approach to the phylogeny of the Caninae allowed a reduction in the level of incongruence between a morphological and a mtDNA data sets, and led to a better tuning of their common phylogenetic signal. After controlling for taphonomic biases and obtaining adequate phylogenetic trees, I search for correlates of speciation and extinction rates in modern carnivoran. The results, albeit based on a relatively small sample size and not too strong, suggest that lineages of highly social carnivorans have significantly higher extinction rates than carnivoran lineages that live solitarily and/or in small family groups. This pattern may be explained by the combined effect of intense intraguild competition, the Allee effect, and the relatively small effective population sizes in carnivoran lineages that display reproductive suppression.