title: Breeding Young as a Survival Strategy during Earth's Greatest Mass Extinction.
abstract: Studies of the effects of mass extinctions on ancient ecosystems have focused on changes in taxic diversity, morphological disparity, abundance, behaviour and resource availability as key determinants of group survival. Crucially, the contribution of life history traits to survival during terrestrial mass extinctions has not been investigated, despite the critical role of such traits for population viability. We use bone microstructure and body size data to investigate the palaeoecological implications of changes in life history strategies in the therapsid forerunners of mammals before and after the Permo-Triassic Mass Extinction (PTME), the most catastrophic crisis in Phanerozoic history. Our results are consistent with truncated development, shortened life expectancies, elevated mortality rates and higher extinction risks amongst post-extinction species. Various simulations of ecological dynamics indicate that an earlier onset of reproduction leading to shortened generation times could explain the persistence of therapsids in the unpredictable, resource-limited Early Triassic environments, and help explain observed body size distributions of some disaster taxa (e.g., Lystrosaurus). Our study accounts for differential survival in mammal ancestors after the PTME and provides a methodological framework for quantifying survival strategies in other vertebrates during major biotic crises.
authors.affiliation: Karoo Palaeontology, National Museum, Box 266, Bloemfontein, 9300, South Africa.|Department of Zoology and Entomology, University of the Free State, Bloemfontein, 9300, South Africa.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Botha-Brink
authors.affiliation: Florisbad Quaternary Research, National Museum, Box 266, Bloemfontein, 9300, South Africa.|Centre for Environmental Management, University of the Free State, Bloemfontein, 9300, South Africa.
authors.forename: Daryl
authors.initials: D
authors.lastname: Codron
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.|Natural History Museum of Utah, Salt Lake City, UT 84112, USA.
authors.forename: Adam K
authors.initials: AK
authors.lastname: Huttenlocker
authors.affiliation: Integrative Research Center, Field Museum of Natural History, Chicago, IL 60605, USA.
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Angielczyk
authors.affiliation: School of Life Sciences, University of Lincoln, Lincoln LN6 7DL, UK.
authors.forename: Marcello
authors.initials: M
authors.lastname: Ruta
mesh_terms: D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D001842:Bone and Bones / Q000033:anatomy & histology*; D001947:Breeding; D025061:Dinosaurs; D018534:Earth, Planet; D004463:Ecology; D017753:Ecosystem; D053476:Extinction, Biological; D005580:Fossils; D008017:Life Expectancy; D008322:Mammals; D011157:Population Dynamics; D012306:Risk; D014714:Vertebrates