Date of Graduation

7-2020

Document Type

Thesis

Degree Name

Master of Science in Biology (MS)

Degree Level

Graduate

Department

Biological Sciences

Advisor

Jeremy Beaulieu

Committee Member

Sarah DuRant

Second Committee Member

Adam Siepielski

Keywords

Diversification rates, Extinction, Life history traits, Macroevolution, MiSSE

Abstract

A central goal of conservation biology is to identify and understand the factors that lead to extinction. The Earth is currently undergoing a 6th mass extinction event, in large part because of human activity. In the last century, rates of extinction have increased anywhere from 8-100 times the background rate of 2 extinctions per 10,000 species every 100 years. However, there remains a debate over whether certain species are predisposed to a higher extinction risk. In particular, it is not known if the macroevolutionary history of a lineage is a major contributor to the probability of extinction, nor is it clear whether the current rise in extinction rates is due strictly to anthropogenic activity. Using life history trait information and the International Union for Conservation of Nature (IUCN) Red List rankings for bats, birds, and odonates in combination with a novel diversification method, MiSSE (Missing State Speciation and Extinction), we test if there is an evolutionary signal of extinction susceptibility independent of the influence that traits can have on rates of diversification. Phylogenetic and non-phylogenetic regressions were run to determine if any specific traits correlated with extinction risk ranking. We find that there is no correlation between diversification rates and IUCN extinction risk. However, larger clutch sizes and range sizes correlated with lower extinction risk and that longer generation lengths for birds did correlate with higher levels of extinction risk. We found no correlation of extinction risk and life history traits in bats and odonates. Our modeling suggests that other factors, such as human-mediated activities, better explain the increased extinction rates.

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