Chloe Davis

Date of Award

5-2024

Degree Type

Honors College Thesis

Academic Program

Biological Sciences BS

Department

Biological Sciences

First Advisor

Jake Schaefer, Ph.D.

Advisor Department

Biological Sciences

Abstract

Understanding the origins of reproductive isolation between closely related species is foundational to evolutionary and ecological research. Recent reviews have documented contemporary hybridization between a large portion of species. A greater knowledge of reproductive isolation and its components are vital to expanding conservation efforts for threats such as those to species persistence and community processes. However, there is a lack of clear understanding of how isolating mechanisms evolve throughout many systems where hybridization is prominent. Individuals within the Fundulus notatus species complex (F. notatus, F. olivaceus, and F. euryzonus) readily hybridize at many contact zones replicated throughout their broadly overlapping ranges in the southeastern United States. However, recent work has highlighted high variability in hybridization rates across replicated zones (zones range from <1% to >30% individuals of hybrid ancestry). To better understand the mechanisms controlling hybridization rates across species contact zones, I conducted mate-choice trials between individuals from populations within the Fundulus notatus species complex that freely hybridize and those that do not. The experimental set up allowed individuals free choice of a conspecific or heterospecific over the course of 6-hour trials. During that time, movement was monitored and tracked for each individual through an artificial intelligence software integrated into video cameras. From there, I used temporal proximity of individuals as a metric of mate preference and to quantify the mode of sexual selection. I observed significant species and population differences in mate preferences. Female F. notatus exhibited greater selectivity compared to F. olivaceus. Within F. notatus, there were different levels of species recognition among the two populations (Ouachita population and Pascagoula population). Additionally, body size influenced mate choice differently between the species. My results allow us to consider sexual selection as the driver of reproductive isolation among the F. notatus species complex. Future research on the genetic basis of species recognition and mate choice behaviors offers promising opportunity to deepen the understanding of reproductive isolation between closely related species.

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