META-ANALYSIS OF EXTINCTION SELECTIVITY IN FOSSIL BIVALVES AND GASTROPODS

Biotic and abiotic traits influence marine bivalve and gastropod extinction dynamics and the effect of these traits on extinction selectivity may be mediated by environmental conditions and extinction intensity. Extinction selectivity in fossil mollusks has been studied extensively for 50 years, but few attempts have been made to synthesize these results across extinctions of different magnitudes, causal mechanisms, and geographic extents.

In this study, we used a Mantel-Haenszel meta-analytic framework to address three main questions: (1) What patterns of extinction selectivity do marine bivalves and gastropods exhibit with respect to geographic range, life habit, and abundance? (2) How does the intensity and direction of extinction selectivity differ during background, regional, and mass extinctions? (3) How are the causal mechanisms of extinction (e.g. ocean acidification, climate change) reflected in patterns of ecological extinction selectivity?

We generated a database of 400+ raw (i.e. extinct vs. surviving) and statistical effect sizes of extinction selectivity compiled from 34 studies conducted from 1973-2011. Together, these studies examined extinction selectivity with respect to geographic range, abundance, and life habit during periods of background, regional, and mass extinctions from the Devonian to the Pleistocene. These data were then parsed according to extinction intensity to examine whether selectivity regimes differ in background versus mass extinctions. We also compared patterns of extinction selectivity across events with similar causal mechanisms. Preliminary results indicate increased extinction risk for endemic taxa compared to cosmopolitan taxa. The results from our synthetic analyses may help predict modern molluscan extinction dynamics in ecosystems in which similar proximal drivers of extinction selectivity are operating.