Taxon characteristics that promote survivorship through the Permian–Triassic interval: transition from the Paleozoic to the Mesozoic brachiopod fauna

Abstract

Examination of organismal characteristics which promote survivorship through both background and mass extinctions may reveal general ecological principles potentially critical to modern conservation efforts. This study explores survivorship of brachiopods, a highly diverse and abundant Paleozoic clade, through the mid-Permian to mid-Triassic interval, which includes the greatest mass extinction in the history of metazoan life. This interval of time separates two of the major Phanerozoic evolutionary faunas. In this regard, survivorship across any one extinction during the interval would not have been relevant if the survivor went extinct shortly after the extinction event; surviving background extinction is as important as surviving a mass extinction. Similarly, taxa that survived but failed to rediversify also were not major elements of the Mesozoic evolutionary fauna. Thus, the analysis aims to analyze survivorship not just across a single extinction but across the entire mid-Permian to mid-Triassic; only survivors through the entire interval can be the ancestors of the Mesozoic clades.Fewer brachiopod genera survived the interval than did brachiopod clades, suggesting that pseudoextinction or insufficient sampling could be a problem in analyzing these extinctions; thus, survivorship analysis should be conducted at the clade level. Nine characteristics were examined for generic representatives of 20 North American brachiopod clades, five of which survived both Permian extinctions and the subsequent earliest Triassic transitional interval. Characteristics include both those that operate on global scales and those that operate on the higher-resolution scales of individuals and populations.Survivors were significantly smaller and occurred less frequently than victims. Mean diversity of communities in which survivors were present was significantly greater. The finding that rare taxa belonging to high-diversity communities were more likely to survive runs counter to traditional predictions. However, these results are consistent with recent studies suggesting that higher diversity within a trophic level may create a buffer, as surviving taxa quickly occupy the vacant niche space of the victims. As size, abundance, and community diversity are all statistically related, the small size of survivors may be an artifact of reduced biovolume per taxon in a diverse community.No significant relationship exists between global-scale processes and survivorship of brachiopods through the mid-Permian to mid-Triassic. The results suggest that ecological processes can strongly influence global extinction patterns.

Local and global abundance associated with extinction risk in late Paleozoic and early Mesozoic gastropods

“…Global occurrence frequency is associated with genus extinction risk, but this finding could be accounted for by correlation between occurrence frequency and geographic range. Leighton and Schneider (2008) found no significant association between abundance and extinction risk, but interpretation of their results is complicated by the long time gap between the age of the samples (Late Pennsylvanian and Early Permian) and the timing of the extinction event (end-Permian).…”

Diversity-dependence brings molecular phylogenies closer to agreement with the fossil record

“…0.11 calculated using fossils [9]. Although estimates of fossil per-genus extinction rates do not necessarily translate directly to species extinction rates [38,39], the genus extinction rate may give a lower bound estimate of the species extinction rate [40]. Repeating the likelihood calculations with m fixed at 0.11, we find that the likelihood of the diversity-dependent model (DDLþE) is only slightly lower (figure 2d) than when m is free to vary and much higher than of the CR birth-death model.…”

Precocious sexual dimorphism and the Lilliput effect in Neo‐Tethyan Ostracoda (Crustacea) through the Permian–Triassic boundary

“…; Peng et al . ; Leighton and Schneider ), the gastropods (Fraiser and Bottjer , ; Payne ), the bivalves (Hayami ), the ammonoids (Yang et al . ), the foraminifers (Jenny‐Deshusses ; Song et al .…”