CONGRUENT PHYLOGENETIC AND FOSSIL SIGNATURES OF MAMMALIAN DIVERSIFICATION DYNAMICS
Our results revealed that the ruminant’s fossil record and phylogeny reflect congruent evolutionary processes. The concordance is especially strong for the last 25 my, when living groups became a dominant part of ruminant diversity. Also the high faunal replacement and lineage depletion in Eocene and Oligocene times marked the shape of the living ruminants tree to a great extent, restricting the number of lineages that it recovers from the fist half of the analysis interval. This is probably the case of other groups of land vertebrates.
Both increasing extinction or decelerating speciation can cause rate slowdowns in living taxa trees. Distinguishing between these alternatives is challenging if just neontological information is available. Interestingly, our combined analysis suggest that the early Miocene post-radiation slowdown detected in living ruminant trees was probably rendered by a speciation slowdown coupled with constant, moderate extinction. Thus, this slowdown in the living ruminant tree is rendered at the end of an expansion phase of the modern forms and not by extinction increasing above speciation. On the contrary, we detected a recent deceleration in phylogenetic rates that is probably connected to rapid extinction triggered by recent climatic fluctuations.