DISSERTATION RESEARCH: The evolution of complexity: tests of the ecological drivers of eye size evolution in Trinidadian killifish (Rivulus hartii)

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Understanding the evolution of complex organs, such as the eye, is a long-standing goal in evolutionary biology. The intricate structure of the eye is frequently presented as an example that challenges our understanding of evolution by natural selection. Eye size and structure vary tremendously across species and it has been hypothesized that this variation is the result of contrasting ecological pressures, such as differing light levels in different environments. This project's researchers recently showed that predation is associated with evolutionary changes in in the eye size of a killifish on the island of Trinidad. This proposal will build upon this previous research to understand how and why predators select for shifts in eye size. Such work will enhance comprehension of the conditions that favor the evolution of complex traits such as the vertebrate eye. This research will be incorporated into educational modules that will be presented at outreach events to further enhance the public's understanding of evolution by natural selection.Eye size is positively correlated with the visual capacity of an organism. In turn, vision is closely linked to behaviors that directly and indirectly influence fitness. This connection between variation in eye size and visual aptitude, behavior, and fitness provides the raw materials for divergent ecological conditions to drive evolutionary shifts in eye size. Trinidadian killifish (Rivulus hartii) are found in fish communities on the island of Trinidad that vary in predation intensity. Increased predation is associated with genetically based declines in eye size. This work established a clear link between an ecological selective force and evolutionary shifts in eye size, but it does not establish causation, nor does it explain why predators select for a smaller eye size. This project will leverage a multifaceted approach that includes comparative mark recapture experiments and perturbation experiments in the lab and nature to: (1) quantify how selection operates on eye size in nature, and (2) experimentally test the influence of predators on eye size evolution.