Molecular Evolution of Visual System Genes in Fishes

For many species, vision contributes to a number of fitness-related tasks, including mating and the detection of prey and predators. Selection on the visual system should therefore be strong, especially when ecological or genomic changes open new avenues for evolutionary changes. Visual system pro...

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Main Author: Weadick, Cameron James
Other Authors: Chang, Belinda
Language:en_ca
Published: 2012
Subjects:
Online Access:http://hdl.handle.net/1807/32333
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spelling ndltd-LACETR-oai-collectionscanada.gc.ca-OTU.1807-323332014-01-03T03:43:33ZMolecular Evolution of Visual System Genes in FishesWeadick, Cameron JamesMolecular EvolutionOpsinsCrystallinsFishes0306For many species, vision contributes to a number of fitness-related tasks, including mating and the detection of prey and predators. Selection on the visual system should therefore be strong, especially when ecological or genomic changes open new avenues for evolutionary changes. Visual system proteins are thus attractive systems for molecular evolutionary analyses. This thesis presents a collection of evolutionary studies on two gene families, opsins and crystallins. Opsin proteins determine the wavelengths of light detected by the retina, while crystallin proteins contribute to lens transparency and refractory power. My studies focus on teleost fishes, because teleost visual ecology is exceptionally diverse and because gene duplication is common in this group. In Chapter One, I outline the relevance of protein variation to organismal evolution and describe the analytical methods employed throughout this thesis. Chapter Two considers the long-wavelength sensitive (LWS) opsins of the guppy (Poecilia reticulata). The guppy is shown to possess multiple LWS opsins that have accumulated differences at functionally important amino acid sites since duplicating. Chapter Three focuses on the guppy’s main predator, the pike cichlid Crenicichla frenata, which is shown to have a greater capacity for short-wavelength vision than previously believed. However, this cichlid possesses three fewer opsins than closely-related African cichlids, a difference partly due to duplication of a green-sensitive (RH2) opsin in African cichlids. In Chapter Four, this RH2 duplication event is studied in greater depth; variation in selective constraint is documented following gene duplication and between species from different lakes. Some of the analytical methods employed in Chapter Four were newly developed, as detailed in Chapter Five, where a test for functional divergence among clades is evaluated and then improved upon through the presentation of a new null model that better accommodates among-site variation in selection. In Chapter Six, phylogenetic relationships within the βγ lens crystallin superfamily are clarified, and the functionally distinct γN family is shown to have evolved conservatively compared to other crystallin families. The thesis concludes with suggestions for future directions for evolutionary research on opsins and crystallins, and summarizes recent work that has built on these studies.Chang, BelindaRodd, F. Helen2012-032012-03-26T20:25:25ZNO_RESTRICTION2012-03-26T20:25:25Z2012-03-26Thesishttp://hdl.handle.net/1807/32333en_ca
collection NDLTD
language en_ca
sources NDLTD
topic Molecular Evolution
Opsins
Crystallins
Fishes
0306
spellingShingle Molecular Evolution
Opsins
Crystallins
Fishes
0306
Weadick, Cameron James
Molecular Evolution of Visual System Genes in Fishes
description For many species, vision contributes to a number of fitness-related tasks, including mating and the detection of prey and predators. Selection on the visual system should therefore be strong, especially when ecological or genomic changes open new avenues for evolutionary changes. Visual system proteins are thus attractive systems for molecular evolutionary analyses. This thesis presents a collection of evolutionary studies on two gene families, opsins and crystallins. Opsin proteins determine the wavelengths of light detected by the retina, while crystallin proteins contribute to lens transparency and refractory power. My studies focus on teleost fishes, because teleost visual ecology is exceptionally diverse and because gene duplication is common in this group. In Chapter One, I outline the relevance of protein variation to organismal evolution and describe the analytical methods employed throughout this thesis. Chapter Two considers the long-wavelength sensitive (LWS) opsins of the guppy (Poecilia reticulata). The guppy is shown to possess multiple LWS opsins that have accumulated differences at functionally important amino acid sites since duplicating. Chapter Three focuses on the guppy’s main predator, the pike cichlid Crenicichla frenata, which is shown to have a greater capacity for short-wavelength vision than previously believed. However, this cichlid possesses three fewer opsins than closely-related African cichlids, a difference partly due to duplication of a green-sensitive (RH2) opsin in African cichlids. In Chapter Four, this RH2 duplication event is studied in greater depth; variation in selective constraint is documented following gene duplication and between species from different lakes. Some of the analytical methods employed in Chapter Four were newly developed, as detailed in Chapter Five, where a test for functional divergence among clades is evaluated and then improved upon through the presentation of a new null model that better accommodates among-site variation in selection. In Chapter Six, phylogenetic relationships within the βγ lens crystallin superfamily are clarified, and the functionally distinct γN family is shown to have evolved conservatively compared to other crystallin families. The thesis concludes with suggestions for future directions for evolutionary research on opsins and crystallins, and summarizes recent work that has built on these studies.
author2 Chang, Belinda
author_facet Chang, Belinda
Weadick, Cameron James
author Weadick, Cameron James
author_sort Weadick, Cameron James
title Molecular Evolution of Visual System Genes in Fishes
title_short Molecular Evolution of Visual System Genes in Fishes
title_full Molecular Evolution of Visual System Genes in Fishes
title_fullStr Molecular Evolution of Visual System Genes in Fishes
title_full_unstemmed Molecular Evolution of Visual System Genes in Fishes
title_sort molecular evolution of visual system genes in fishes
publishDate 2012
url http://hdl.handle.net/1807/32333
work_keys_str_mv AT weadickcameronjames molecularevolutionofvisualsystemgenesinfishes
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