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Author ORCID Identifier

0000-0002-1393-6479

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Organismic and Evolutionary Biology

Year Degree Awarded

2019

Month Degree Awarded

May

First Advisor

R. Craig Albertson

Second Advisor

Susan Foster

Third Advisor

Courtney Babbitt

Fourth Advisor

Jeffrey Podos

Subject Categories

Integrative Biology

Abstract

Understanding the generation of phenotypic variation by linking it to genetic variation has long been a focus of evolutionary biology; this framework has successfully been implemented in a variety of studies across the tree of life1,2. However, our understanding of the phenotype remains incomplete until we account for a myriad of interactions that influence the genotype-phenotype map, including interactions between traits (TxT), interactions between genes and the environment (GxE), as well as the ways in which various types of interactions are nested within and build upon one another (e.g., (TxT)xG). My dissertation aims to contribute to filling this gap by dissecting the interactions that influence variation in ecologically-relevant phenotypes in a model adaptive radiation: African cichlid fish. We utilize a stereotypical ecomorphological axis of variation, in which benthic fish scrape and bite prey off the rocky substrate while pelagic fish suction prey out of the water column3. Chapter 1 focuses predominantly on understanding the genetics that underlie variation across disparate anatomical units which relate to both the feeding and locomotive systems in these fish (i.e. a [[TxT]xG] interaction). We found that the genotype–phenotype map for fin shape is largely distinct from other morphological characters including body and craniofacial shape. These data suggest that key aspects of fin, body and jaw shape are genetically modular and that the coordinated evolution of these traits in cichlids is more likely due to common selective pressures than to pleiotropy or linkage. Chapter 2 dissects the genetics underlying those same anatomical units across environments, representing a more complex model of putative interactions (i.e. [[[TxT]xG]xE]). In more specific terms, this chapter aims to understand the genetic basis of phenotypic plasticity, We found a substantial degree of modularity in the plastic responses at both the morphological and genetic levels. In all, our data provide minimal support for the existence of global regulators of plasticity, serve as an important step toward further characterizing the genetic basis of plasticity in cichlids, and provide a list of candidate loci for future functional analyses. Chapter 3 delves more into a specific GxE interaction in craniofacial morphology, and for the first time in a vertebrate system tests the functional capacity of a signal transduction pathway to mediate the magnitude of a plastic response. We verify important roles for Hh signaling in this response, thus filling important gaps in the field. Together, my dissertation demonstrates how a broadly integrative approach to evolutionary biology can allow us to layer multiple lines of empirical evidence onto strong theoretical frameworks and further generate insights into the production and maintenance of real-world variation.

Available for download on Sunday, May 10, 2020

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