Deep Time Drivers of Evolutionary Entities

Species are known to reflect evolutionary significant units (ESUs), however still deliberated is the potential existence and reality of higher units. The somewhat esoteric nature of naming higher taxa is not grounded in any evolutionary process, yet higher evolutionary significant units (HESUs) have been argued to be real, and patterns of shared processes likely drive the formation of distinct evolutionary entities in deep time. The veracity of this, however, remains unresolved. Here, I show that HESUs do exist within the mammalian clade Afrotheria, defined using a range of potential metrics. I constructed a phylogeny using fossil taxa, and applied it to investigate rates of diversification, and how these rates change with the presence or absence of extinct species. I used this phylogeny further when exploring the zoogeographic history of the clade, and for studying significant shifts in trait evolution, focusing on body mass and cranium morphology. Finally, I revisited diversification and searched for clusters of branching rates on the tree, and tested their stability in deep time. I found that shared histories of diversification, phenotype and zoogeography can all play a role in delineating HESUs. I further notice the important function of extinction as a macroevolutionary process that shapes many patterns within the clade, as well as the previously masked outcomes revealed when extinct taxa are included in analyses. My results here provide additional support to the reality of evolutionarily significant higher taxa and allow us to consider future areas of intriguing research into the comprehension of macroevolutionary dynamics.