Date Thesis Awarded
Honors Thesis -- Access Restricted On-Campus Only
Bachelors of Science (BS)
Jonathan D. Allen
Marine bivalve and gastropod extinction selectivity dynamics are driven by important factors, such as ecological traits, extinction intensity, and environmental changes. However, the relationships among these factors and their effects on gastropod and bivalve taxa over varying geographic and temporal scales are poorly understood. For example, extinction selectivity in fossil molluscs has been studied extensively for 50 years, but no attempt has been made to synthesize these results across extinctions of different magnitudes, causal mechanisms, and geographic extents. The goal of this study is to perform a meta-analysis of extinction selectivity studies in order to answer three pertinent questions: What patterns of extinction selectivity do marine bivalves and gastropods exhibit with respect to geographic range and life habit? How does the intensity and direction of extinction selectivity differ according to extinction rate? How are the causal mechanisms of extinction reflected in patterns of extinction selectivity? To answer these questions, I generated a database consisting of 178 datapoints (i.e. extinct vs. surviving) compiled from 34 studies conducted from 1973-2011. Together, these studies examined extinction selectivity with respect to geographic range and life habit during periods of background, regional, and mass extinctions from the Ordovician to the Pleistocene. I converted these data into log-odds ratios and weighted them with respect to sample size and statistical significance. We also compared patterns of extinction selectivity across events with according to extinction rate and causal mechanisms. This analysis strongly supports the role of geographic range in determining the direction of extinction selectivity. I found no relationship between extinction magnitude and selectivity. However, it does support a robust role for causal mechanism in determining patterns of extinction selectivity. Therefore, understanding the effects of causal mechanisms such as sea level and global temperature change on selectivity patterns is of pressing importance in modeling what is anticipated to be Earth's sixth mass extinction.
Orzechowski, Emily, "Meta-analysis of Extinction Selectivity in Fossil Marine Bivalves and Gastropods" (2012). Undergraduate Honors Theses. William & Mary. Paper 551.
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