The evolution of eyes: Physiology, ecology, and selection at the population scale.

Variation in the structure and morphology of eyes is thought to be associated with environmental variation that influences the benefits and costs of vision. Comparisons among species have borne this out, but a lack of within-species investigation means that we do not know how differences among species arise. This project aims to determine the ecological correlates of eye size in the model crustacean Daphnia, to determine how visual capabilities are influenced by eye size, to quantify the costs of vision, and to ascertain how these factors jointly influence the effects of vision on fitness in different environmental contexts. Daphnia serve as an important model for monitoring environmental effects, such as water quality. Together, these elements will provide novel insight into functional consequences of variation of an important sensory system and advance our understanding of why visual systems differ, thus promoting the progress of science. New discoveries in how different eyes accomplish similar tasks have the potential to enable improvements in visual sensors in diverse technological fields. Training for the next generation of scientists (graduate and undergraduate) will be provided that integrates perspectives on visual systems from multiple biological disciplines. In addition, an educational computer-based game will be developed as a tool for teaching integrative biology, including concepts from physiology and population biology. This project advances NSF's priorities in Biotechnology. This project combines fieldwork, physiological measurements, and experiments to study how physiology and ecology drive selection on eye size in Daphnia. The major goal is to determine how visual performance and costs scale with eye size, and then to combine those relationships with ecological information to understand the advantages and disadvantages of different eyes in different environments. Four primary research components are included: 1) fieldwork that examines the phenotypic distribution of eye sizes in the context of light availability, predation, and resource abundance; 2) empirical measurement of effects of eye size on visual performance using a combination of morphological analysis, electrophysiological tests, and behavioral experiments; 3) quantification of the costs of (larger) eyes with physiological measures of energetic demand, and common garden life tables to measure reproductive costs. This work will capitalize on both natural variation of eye size and our ability to perform experimental eye removals; 4) determination of the fitness consequences of eye size variation in natural populations and experimental mesocosms. This will combine fieldwork grounded in natural variation with experimental manipulations of light, predators, and resources. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.