Using the Price Equation to Quantify Species Selection and Other Macroevolutionary Forces in Cretaceous Molluscs
Date
2019-08-12
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Abstract
Species selection and other macroevolutionary forces are challenging processes to study and quantify when using fossil data. Here, I used the Price equation to analyze changes in geographic range sizes prior to and during a mass extinction event to estimate the relative contribution of three macroevolutionary processes (species selection, anagenesis, and immigration). I also tested the hypothesis that larger geographic range size increases a group’s survivability during mass extinctions. I applied a similar method to Rankin et al. (2015) to study marine gastropods and bivalves of the Gulf and Atlantic Coastal Plain (originally studied by Jablonski (1987)) over the last 16 million years of the Cretaceous Period. I found three major changes in mean geographic range size shared by both gastropods and bivalves during the end-Cretaceous: an increase in mean range size during the late Campanian, a decrease in the mid-Maastrichtian, and an increase near the end of the Cretaceous Period (late Maastrichtian). The Price Equation indicates that the late Campanian increase in geographic range size was attributable primarily to immigration, the mid-Maastrichtian decrease was due to different combinations of the three processes (species selection, anagenetic change, and immigration) in gastropods and bivalves, and the late Maastrichtian increase was attributable to species selection. These changes in geographic range size coincide with a marine transgression event, a period of global climate change, and a marine regression event, respectively. A statistically significant correlation between larger geographic range size and increased survivability was found for one time increment (approximately four million years before the KPg boundary). This study shows that the relative contribution of interacting macroevolutionary processes fluctuated over the end-Cretaceous extinction event and suggests that large geographic range size can increase survivability under certain conditions leading up to a mass extinction.
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Keywords
macroevolution, species selection, anagenetic change, immigration
Citation
Jordan, K. J. (2019). Using the Price Equation to Quantify Species Selection and Other Macroevolutionary Forces in Cretaceous Molluscs (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.