Evolution and Plasticity of Fish Color Vision

The huge biodiversity of teleost fish is mirrored by the phenotypic diversity of their visual traits. Fish inhabit a wide range of aquatic ecosystems that differ in their water clarity and photic conditions. Photic environments can vary widely in their spectral composition and light availability, for example, turbid rivers, as opposed to clear lakes. The number of photons and their wavelengths inevitably affect the conspicuousness of the signals and detection of visual cues within a given light environment. The strong attenuation of light in aquatic media shapes sensory biology; thus, many studies in visual ecology have focused on photic conditions as drivers of evolution in visual systems and signals. Over multiple generations, environmental drivers acting as selective pressures might lead visual traits to diverge genetically, i.e., phenotypic evolution of teleost vision. Complementarily, short-term environmental fluctuations such as seasonal or episodic photic variability might shape the phenotypic plasticity of fish vision, i.e., the ability to modulate visual perception within one generation. In this thesis, I focus on two distantly related taxonomic groups, Neotropical cichlids (Cichlidae) and Nearctic centrarchids (Centrarchidae), which overlap in their ecologies, but differ widely in their sensory biology. Cichlids exhibit highly tunable sensory biology owing to both phenotypic plasticity and genetic differentiation. In contrast, visual traits in Centrarchids exhibit relatively canalized phenotypes, with little environmentally driven visual diversity. In this dissertation, I aim to understand the molecular basis of phenotypic diversity in fish and uncover common mechanisms underlying the evolution and plasticity of fish color vision. To this end, I first perform a meta-analysis of opsin gene expression plasticity to uncover the factors and phylogenetic signal governing this trait. Second, I investigate genetic and environmental influences on the temporal dynamics of plasticity in opsin gene expression. Finally, I characterize the visual system of six centrarchid species with long evolutionary divergence yet limited intra-specific variation.<p></p>