Testing extinction rates across various modes of life in Bivalvia during the end-Cretaceous mass extinction

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dc.contributorMarkley, Michelle
dc.contributorYoung, Derek
dc.contributor.advisorMcMenamin, Mark
dc.contributor.authorSullivan, Johanna
dc.date.accessioned2023-05-19T17:00:51Z
dc.date.available2023-05-19T17:00:51Z
dc.date.gradyear2023en_US
dc.date.issued2023-05-19
dc.description.abstractMass extinctions disrupt the balance of clade richness across the tree of life, dramatically and permanently altering the ecological landscape (Foote, 1997; Jablonski, 2005; Sclafani et al., 2018). Certain groups of organisms are lost to extinction, while others persist through the survival of individual lineages (Jablonski, 2002; Jablonski, 2005; Sclafani et al., 2018; Wan et al., 2021). The difference between survival and extinction could be connected to three key traits–mobility, feeding, and tiering–which combined make up an organism’s mode of life (MOL). I analyzed extinction selectivity across all bivalve genera known to exist during the end-Cretaceous mass extinction (KPg) to determine which modes of life fared better and which of the three MOL traits most contributed towards genus survival. Of the fifteen unique MOLs, and the thirteen MOLs that had enough samples to properly analyze, only one went extinct (immobile, intermediate epifaunal, suspension/photosymbiotic feeder). Despite the relative stability of the MOLs, there were clearly groups hit harder than others. Semi-infaunal suspension feeders suffered the second greatest extinction level regardless of whether the taxa were mobile or sessile (81% for mobile taxa and 72% for sessile taxa) while immobile suspension feeding boring bivalves had the lowest extinction rate (<25%). Separating the three MOL traits, I found tiering to be the most important trait in guarding against extinction with feeding and mobility being of secondary and tertiary importance respectively. More exposed bivalves (intermediate epifaunal or semi-faunal) suffered the greatest extinction rates (100% and 77% respectively) while less exposed bivalves (boring and deep infaunal) had the lowest extinction rates (<25% and 43% respectively). Bivalve groups that relied on a combination of suspension feeding and photosynthesis (i.e. rudists) suffered a complete extinction whereas groups that used a chemosymbiotic strategy to feed suffered a less than 25% extinction rate. There is also a slight trend towards higher levels of mobility increasing survival rates (58% of immobile bivalves went extinct and 50% of mobile bivalves went extinct). There appears to be intersections between tiering and feeding that affects extinction rates; greater amounts of natural coverage and more reliable sources of food likely protected certain groups against extinction.en_US
dc.description.sponsorshipGeologyen_US
dc.identifier.urihttp://hdl.handle.net/10166/6410
dc.language.isoen_USen_US
dc.rights.restrictedpublicen_US
dc.subjectbivalvesen_US
dc.subjectmacroevolutionen_US
dc.subjectmass extinctionsen_US
dc.subjectextinction selectivityen_US
dc.subjectmode of lifeen_US
dc.subjectmobilityen_US
dc.subjecttieringen_US
dc.subjectfeeding strategyen_US
dc.subjectinfaunalen_US
dc.subjectepifaunalen_US
dc.subjectextinction rateen_US
dc.subjectCretaceousen_US
dc.subjectBivalviaen_US
dc.titleTesting extinction rates across various modes of life in Bivalvia during the end-Cretaceous mass extinctionen_US
dc.typeThesis
mhc.degreeUndergraduateen_US
mhc.institutionMount Holyoke College

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