PHYLOGENETIC SIGNAL IN EXTINCTION SELECTIVITY IN DEVONIAN TEREBRATULIDE BRACHIOPODS

Determining which biological traits influence taxonomic longevity is critical for explaining macroevolutionary pattern and for conserving existing biodiversity. Two approaches have been used, largely in isolation, to investigate the contributions of traits to variation in extinction and origination rates over time and among clades: analyses of taxonomic occurrence patterns in the fossil record and comparative phylogenetic analyses of extant taxa. Paleobiological data allow one to capitalize upon the rich empirical record of extinction over geologic time. However, most previous paleobiological studies of extinction selectivity have not considered phylogenetic relationships. This omission inflates the degrees of freedom in statistical analyses and leaves unresolved the question of whether, or to what extent, different biological traits are phylogenetically conserved. Here we investigate global patterns of extinction selectivity in Devonian terebratulide brachiopods, and compare the results of taxonomic versus phylogenetic approaches. Conventional taxonomic analyses show a significant positive association between geographic range size and genus duration, and no association between body size and genus duration. Considering these traits in a phylogenetic framework reveals significant similarity in body size and duration among closely related lineages, whereas geographic range size shows little phylogenetic signal. We use phylogenetic regression to account for shared evolutionary history and find a significant positive association between range size and duration that is also phylogenetically structured. The estimated range size-duration relationship is weaker in the phylogenetic versus taxonomic analysis due to the down-weighting of closely-related genera that were both broadly-distributed and long-lived. These results are consistent with other recent studies of extant and extinct taxa that have found that closely related lineages tend to be at similar risk of extinction, and show that phylogeny can affect, but not wholly explain, the range size-duration relationship observed in many macroevolutionary analyses. Comparative analyses of paleobiological data may yield considerable insights into the processes underlying macroecological and macroevolutionary patterns.