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Diversification Rate Shifts in Early Amniotes (free pdf)



Ben Creisler
bcreisler@gmail.com

A new paper in open access:

Neil Brocklehurst, Marcello Ruta, Johannes Müller & Jörg Fröbisch (2015)
Elevated Extinction Rates as a Trigger for Diversification Rate
Shifts: Early Amniotes as a Case Study.
Scientific Reports 5, Article number: 17104 (2015)
doi:10.1038/srep17104
http://www.nature.com/articles/srep17104


Tree shape analyses are frequently used to infer the location of
shifts in diversification rate within the Tree of Life. Many studies
have supported a causal relationship between shifts and temporally
coincident events such as the evolution of “key innovations”. However,
the evidence for such relationships is circumstantial. We investigated
patterns of diversification during the early evolution of Amniota from
the Carboniferous to the Triassic, subjecting a new supertree to
analyses of tree balance in order to infer the timing and location of
diversification shifts. We investigated how uneven origination and
extinction rates drive diversification shifts, and use two case
studies (herbivory and an aquatic lifestyle) to examine whether shifts
tend to be contemporaneous with evolutionary novelties. Shifts within
amniotes tend to occur during periods of elevated extinction, with
mass extinctions coinciding with numerous and larger shifts.
Diversification shifts occurring in clades that possess evolutionary
innovations do not coincide temporally with the appearance of those
innovations, but are instead deferred to periods of high extinction
rate. We suggest such innovations did not cause increases in the rate
of cladogenesis, but allowed clades to survive extinction events. We
highlight the importance of examining general patterns of
diversification before interpreting specific shifts.