Date of Award

2023

Document Type

Dissertation

Degree Name

Ph.D.

Organizational Unit

College of Natural Science and Mathematics, Biological Sciences

First Advisor

Robin M. Tinghitella

Second Advisor

Erica L. Larson

Third Advisor

Anna A. Sher

Fourth Advisor

Jonathan P. Velotta

Keywords

Behavioral ecology, Diversification, Evolutionary biology, Rapid evolution, Sexual signals, Teleogryllus oceanicus

Abstract

Understanding how the early stages of sexual signal diversification proceed is of critical importance because the nature of these microevolutionary dynamics can directly shape species trajectories and macroevolutionary patterns. Unfortunately, studying signal diversification is challenging because signals involve complex interactions between behavioral, morphological, and physiological components, many of which can only be measured in real time. Here we had the opportunity to directly study this process with the recent increase in sexual signal variation in Hawaiian populations of the Pacific field cricket (Teleogryllus oceanicus). In Hawaii, male song attracts both female crickets and a deadly acoustically orienting parasitoid fly (Ormia ochracea). This interaction led to the emergence of a silent morph that evades costly parasitism, and, more recently, novel male morphs that produce attenuated songs and may balance the natural-sexual selection conflict differently. We capitalize on this case of rapid evolution to answer questions about the earliest stages of signal diversification by 1) characterizing novel signal diversity, 2) investigating mechanisms underlying the production of new signals, 3) tracking evolutionary change in the relative abundance of morphs, and 4) interrogating the selective landscape driving such rapid evolutionary change. We first characterize the signals of novel cricket morphs, finding that several differ in how their wings generate song. This work illustrates how the rewiring of wing-song relationships can facilitate phenotypic diversification. Evidence also points to ongoing rapid evolution within and among populations. Our repeated sampling over approximately 12 generations revealed that some novel morphs are increasing in commonality within populations, some are spreading across the archipelago, and at least one has already diverged across island populations. Finally, we investigate ultimate explanations for such rapid evolution by characterizing major selective pressures imposed by intended and unintended receivers. We find that each novel morph’s sexual signal is a unique evolutionary solution to the challenge of attracting mates while evading parasitism. Overall, our findings demonstrate the rapid pace of evolution in island populations, provide insights into the origins and divergence of new sexual signals over time, and illustrate the utility of this emerging model system as a microcosm for answering fundamental questions in evolutionary biology.

Publication Statement

Copyright is held by the author. User is responsible for all copyright compliance.

Rights Holder

James H. Gallagher

Provenance

Received from ProQuest

File Format

application/pdf

Language

en

File Size

134 pgs

Discipline

Biology, Evolution and development, Ecology

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