title: Elevated Extinction Rates as a Trigger for Diversification Rate Shifts: Early Amniotes as a Case Study.
abstract: 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.
authors.affiliation: Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, D-10115 Berlin, Germany.
authors.forename: Neil
authors.initials: N
authors.lastname: Brocklehurst
authors.affiliation: School of Life Sciences, University of Lincoln, Joseph Banks Laboratories, Green Lane, Lincoln LN6 7DL, UK.
authors.forename: Marcello
authors.initials: M
authors.lastname: Ruta
authors.affiliation: Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, D-10115 Berlin, Germany.|Institut für Biologie, Humboldt-Universität zu Berlin, Invalidenstraße 110, Berlin D-10115, Germany.|Berlin-Brandenburg Institute of Advanced Biodiversity Research, Altensteinstrasse 6, Berlin D-14195, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Müller
authors.affiliation: Museum für Naturkunde, Leibniz-Institut für Evolutions- und Biodiversitätsforschung, Invalidenstraße 43, D-10115 Berlin, Germany.|Institut für Biologie, Humboldt-Universität zu Berlin, Invalidenstraße 110, Berlin D-10115, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Fröbisch
mesh_terms: D000650:Amnion / Q000502:physiology; D000818:Animals; D059001:Aquatic Organisms / Q000145:classification* / Q000235:genetics; D044822:Biodiversity; D053476:Extinction, Biological; D005580:Fossils; D049810:Genetic Speciation; D060434:Herbivory / Q000235:genetics; D015233:Models, Statistical; D010802:Phylogeny