Understanding how reproductive isolation arises between closely related species is central to evolutionary research. Hybridization is widespread across taxa and shaped by interactions among environmental factors, evolutionary history, genetic compatibility, and behavior. These forces often operate nonlinearly across space and time, yet mate choice is frequently assessed under artificial conditions that may not reflect natural behavior. To address this limitation, female mate preference was investigated within the Fundulus notatus species complex, where F. notatus and F. olivaceus hybridize at varying rates across replicate contact zones. Using a free-choice design, behavioral trials were conducted with individuals from populations characterized by high and low hybridization rates, along with F. notatus crosses produced from the divergent populations. During six-hour trials, fish interacted freely in semi-natural arenas while movements were tracked using AI video monitoring. Female association time with conspecific versus heterospecific males was used as a proxy for mate preference. Additionally, male standard length and spot density were measured to assess the influence of morphology on female behavior. Results revealed significant clade-level variation in female association behavior. Preferences for conspecific versus heterospecific males varied predictably with population-level hybridization rates: females from low-hybridizing populations exhibited stronger conspecific preferences, while those from high-hybridizing populations showed weaker discrimination. Clade-cross females displayed intermediate behavior, supporting a genetic basis for variation in mate preference. Furthermore, body size and spot count influenced female association across populations. These findings highlight the role of behavioral isolation in maintaining species boundaries.
","abstract_html":"<p>Understanding how reproductive isolation arises between closely related species is central to evolutionary research. Hybridization is widespread across taxa and shaped by interactions among environmental factors, evolutionary history, genetic compatibility, and behavior. These forces often operate nonlinearly across space and time, yet mate choice is frequently assessed under artificial conditions that may not reflect natural behavior. To address this limitation, female mate preference was investigated within the <em>Fundulus notatus</em> species complex, where <em>F. notatus</em> and <em>F. olivaceus</em> hybridize at varying rates across replicate contact zones. Using a free-choice design, behavioral trials were conducted with individuals from populations characterized by high and low hybridization rates, along with <em>F. notatus</em> crosses produced from the divergent populations. During six-hour trials, fish interacted freely in semi-natural arenas while movements were tracked using AI video monitoring. Female association time with conspecific versus heterospecific males was used as a proxy for mate preference. Additionally, male standard length and spot density were measured to assess the influence of morphology on female behavior. Results revealed significant clade-level variation in female association behavior. Preferences for conspecific versus heterospecific males varied predictably with population-level hybridization rates: females from low-hybridizing populations exhibited stronger conspecific preferences, while those from high-hybridizing populations showed weaker discrimination. Clade-cross females displayed intermediate behavior, supporting a genetic basis for variation in mate preference. Furthermore, body size and spot count influenced female association across populations. These findings highlight the role of behavioral isolation in maintaining species boundaries.</p>","abstract_has_math":false,"creators":["Holderness, Emilee K"],"institution":null,"degree_name":"Master of Science (MS)","degree_level":"Masters Thesis","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Dr. Jake Schaefer","Dr. Brian Kreiser","Dr. Kaitlin Baudier"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-08-01T07:00:00Z","date_published":"2025-08-01T07:00:00Z","updated_at":"2026-07-24T05:45:55Z","subjects":["Prezygotic reproductive isolation","Female mate choice","Hybrid zone dynamics","Fundulus notatus species complex","Behavioral isolation","Free-choice experimental design"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://aquila.usm.edu/masters_theses/1143","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Dr. Jake Schaefer","Dr. Brian Kreiser","Dr. Kaitlin Baudier"]},{"key":"dc:creator","label":"Author","values":["Holderness, Emilee K"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2025-07-01T07:00:00Z"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Masters Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science (MS)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Prezygotic reproductive isolation","Female mate choice","Hybrid zone dynamics","Fundulus notatus species complex","Behavioral isolation","Free-choice experimental design"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://aquila.usm.edu/masters_theses/1143"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Understanding how reproductive isolation arises between closely related species is central to evolutionary research. Hybridization is widespread across taxa and shaped by interactions among environmental factors, evolutionary history, genetic compatibility, and behavior. These forces often operate nonlinearly across space and time, yet mate choice is frequently assessed under artificial conditions that may not reflect natural behavior. To address this limitation, female mate preference was investigated within the Fundulus notatus species complex, where F. notatus and F. olivaceus hybridize at varying rates across replicate contact zones. Using a free-choice design, behavioral trials were conducted with individuals from populations characterized by high and low hybridization rates, along with F. notatus crosses produced from the divergent populations. During six-hour trials, fish interacted freely in semi-natural arenas while movements were tracked using AI video monitoring. Female association time with conspecific versus heterospecific males was used as a proxy for mate preference. Additionally, male standard length and spot density were measured to assess the influence of morphology on female behavior. Results revealed significant clade-level variation in female association behavior. Preferences for conspecific versus heterospecific males varied predictably with population-level hybridization rates: females from low-hybridizing populations exhibited stronger conspecific preferences, while those from high-hybridizing populations showed weaker discrimination. Clade-cross females displayed intermediate behavior, supporting a genetic basis for variation in mate preference. Furthermore, body size and spot count influenced female association across populations. These findings highlight the role of behavioral isolation in maintaining species boundaries.
"]},{"key":"dc:title","label":"Title","values":["Female Preference and Prezygotic Isolation In the Fundulus Notatus Species Complex"]}]}],"canonical_facts":{"dc:contributor":["Dr. Jake Schaefer","Dr. Brian Kreiser","Dr. Kaitlin Baudier"],"dc:creator":["Holderness, Emilee K"],"dc:date.available":["2025-07-01T07:00:00Z"],"dc:description.abstract":["Understanding how reproductive isolation arises between closely related species is central to evolutionary research. Hybridization is widespread across taxa and shaped by interactions among environmental factors, evolutionary history, genetic compatibility, and behavior. These forces often operate nonlinearly across space and time, yet mate choice is frequently assessed under artificial conditions that may not reflect natural behavior. To address this limitation, female mate preference was investigated within the Fundulus notatus species complex, where F. notatus and F. olivaceus hybridize at varying rates across replicate contact zones. Using a free-choice design, behavioral trials were conducted with individuals from populations characterized by high and low hybridization rates, along with F. notatus crosses produced from the divergent populations. During six-hour trials, fish interacted freely in semi-natural arenas while movements were tracked using AI video monitoring. Female association time with conspecific versus heterospecific males was used as a proxy for mate preference. Additionally, male standard length and spot density were measured to assess the influence of morphology on female behavior. Results revealed significant clade-level variation in female association behavior. Preferences for conspecific versus heterospecific males varied predictably with population-level hybridization rates: females from low-hybridizing populations exhibited stronger conspecific preferences, while those from high-hybridizing populations showed weaker discrimination. Clade-cross females displayed intermediate behavior, supporting a genetic basis for variation in mate preference. Furthermore, body size and spot count influenced female association across populations. These findings highlight the role of behavioral isolation in maintaining species boundaries.
"],"dc:identifier":["https://aquila.usm.edu/masters_theses/1143"],"dc:subject":["Prezygotic reproductive isolation","Female mate choice","Hybrid zone dynamics","Fundulus notatus species complex","Behavioral isolation","Free-choice experimental design"],"dc:title":["Female Preference and Prezygotic Isolation In the Fundulus Notatus Species Complex"],"thesis:degree_level":["Masters Thesis"],"thesis:degree_name":["Master of Science (MS)"]},"updated_at":"2026-07-24T05:45:55Z"}