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The genetic, cellular, and evolutionary basis of skin coloration in the highly polymorphic poison frog, Oophaga pumilio

Freeborn, Layla R (2021) The genetic, cellular, and evolutionary basis of skin coloration in the highly polymorphic poison frog, Oophaga pumilio. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Studies of phenotypic variation are undisputedly important to understanding the processes of evolution. Animal coloration is important in many ecological contexts, including thermoregulation, predator avoidance, male-male competition, and mate choice. Given its varied function, animal coloration is frequently characterized by phenotypic variation among and within species. The Central American strawberry poison frog, Oophaga pumilio, is known for exhibiting striking color polymorphism across the Bocas del Toro archipelago of Panama. Despite many studies that aim to understand the selective pressures that generated or maintain this variation, relatively little is known about its underlying genetic and morphological basis. Furthermore, the evolution of color variation in this species has been addressed by phylogenetics and population genetics studies, but they have been limited by the challenges associated with studying recently separated populations. To bridge this gap in our knowledge, I investigated the proximate mechanisms of color variation by leveraging the power of next-generation sequencing to find loci associated with color differences. I found that the genes involved in variation in dorsal background coloration are located across broad regions of the genome, rather than being co-localized in one or a few nearby regions. Next, I investigated the proximate mechanism of color variation by examining the presence and absence of pigment types, ratios of pigments, skin components, and chemical compositions of carotenoid-containing cells. My results suggest that large color variations in O. pumilio are explained by differences in pigment proportions and carotenoid suites, not by the absence of pigment cell types. Finally, I applied a multi-species coalescent approach to a SNP dataset derived from the extensive sampling of O. pumilio from Bocas del Toro, then perform ancestral character state reconstructions of dorsal coloration. These analyses provide a high-resolution estimate of relationships for O. pumilio, despite the challenges associated with recent timescales. The results suggest that vicariance explains pattern of genetic differentiation and support the convergent evolution of dull dorsal coloration. Overall, this dissertation provides an important first step toward understanding the proximate mechanisms of phenotypic variation and provides a much-needed phylogenetic backbone for future studies of this system.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Freeborn, Layla Rlrf18@pitt.edulrf18
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee MemberLee, Miler
Committee MemberRebeiz,
Committee MemberTurcotte,
Committee MemberKronforst, Marcus
Committee MemberMorehouse,
Committee ChairRichards-Zawacki, Corinne
Date: 20 January 2021
Date Type: Publication
Defense Date: 5 October 2020
Approval Date: 20 January 2021
Submission Date: 8 December 2020
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 127
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Biological Sciences
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: genomics, phylogenomics
Date Deposited: 20 Jan 2021 18:37
Last Modified: 20 Jan 2021 18:37

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