Molecular Evolution of Vertebrate Visual Systems

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Determining how organisms adapt to their environments is a fundamental goal of evolutionary biology. Sensory systems, such as vision, are an ideal model to study this topic, as they provide a direct interface between an organism and its environment. The long-term objective of my research program is to better understand the evolution of vertebrate visual systems and how they develop and adapt in response to different sensory environments. My research takes an innovative and integrative approach that combines comparative genomics and evolutionary computational analyses with targeted experiments to provide a comprehensive view of visual system evolution and function at multiple organizational scales. Amphibians (frogs, salamanders, and caecilians) provide an excellent system within which to study the evolution and adaptation of visual systems. They are a diverse group (~8200 species) that has convergently evolved many different life histories and behaviors, including subterranean lifestyles, providing the opportunity to study repeated adaptation in the visual system. Amphibians also encapsulate an important evolutionary transition in vertebrate evolution from aquatic to terrestrial environments, which imposed drastically different spectral and optical constraints on the visual system. This transition between aquatic and terrestrial environments also occurs during the life cycle of many amphibians with the transition from aquatic larvae (tadpoles) to terrestrial juveniles, further providing an opportunity to explore the intersection of evolution and development in adaptation of the visual system. Amphibians also have a novel type of light-sensitive photoreceptor that may enable nocturnal colour vision in dim light when most other animals are colour-blind. Despite these unique aspects of amphibians that make them a particularly compelling model for visual biology, the study of amphibian visual systems has fallen well behind other vertebrate groups. We will conduct the first integrative analysis of visual gene evolution across amphibians providing deep insight into the constraints and opportunities of visual systems to evolving novel solutions to new life history modes and behaviors. Complementary studies of frog and salamander visual gene expression across ontogeny will reveal the role of developmental changes in visual adaptation. We will also investigate visual adaptation in amphibians and reptiles that convergently evolved subterranean lifestyles using comparative genomic approaches. Finally, we will study the novel amphibian photoreceptor using single cell transcriptome sequencing and cellular imaging to uncover its evolutionary and developmental history. This will further lay the foundation for future studies of photoreceptor evolution and development in vertebrates. This research program will create a rich environment for a diverse group of trainees to make major contributions using cutting-edge techniques in evolutionary genomics.