A study of the evolutionary history of birds finds three periods of large-scale increase in species diversification rates. Independent approaches to analyze crown and stem birds have made it challenging to reconstruct the evolution of bird biodiversity within a unified framework. Xing Xu and colleagues analyzed lineage diversification rates through time of three supertrees that combined the published phylogenies of both stem and crown birds. The analysis revealed three distinct large-scale increases in the diversification rate across bird evolutionary history. The first increase, which began between 160 and 170 million years ago and reached its peak between 130 and 135 million years ago, corresponded to the accelerated morphological evolution of key structures for flight among early stem birds. This first radiation of early stem birds from their close dinosaurian relatives is thus likely related to their occupation of a new ecospace--the aerial space. The second increase, which began around 90 million years ago and reached its peak between 65 and 55 million years ago, was associated with cranial modifications among early crown birds that were likely related to diversification in diet and foraging behavior. The third increase, which occurred after around 40-45 million years ago, lacks support from morphological data but has some support from the fossil record. According to the authors, bird biodiversity has been mainly influenced by long-term climatic changes and changes related to the Cretaceous-Paleogene mass extinction event.
Article #20-19865: "Deep time diversity and the early radiations of birds," by Yilun Yu et al.
MEDIA CONTACTS: Xing Xu, Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, CHINA; email: xu.xing@ivpp.ac.cn ; Chi Zhang, Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, CHINA; email: zhangchi@ivpp.ac.cn
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Proceedings of the National Academy of Sciences