Meeting Abstract

4.3  Jan. 4  Is visual performance constrained by body size in Drosophila melanogaster? MERRY, J. W.*; RUTOWSKI, R. L.; Arizona State University; Arizona State University jmerry@asu.edu

Past research on insect eyes has revealed the presence of a strong, allometric relationship between eye size and body size, both within and among species. This finding has been explained as being the result of competing selection pressures: on one hand, selection favoring increased visual performance drives an increase in eye size. On the other, selection favoring reduced costs (mechanical, metabolic, etc) constrains eye size relative to body size. According to this hypothesis, as body size increases, the relative costs of maintaining an eye of a given size decrease, allowing improvement in visual performance via the construction of a larger eye. Here, we present data evaluating the strength of the constraint of body size on eye size in Drosophila melanogaster. To evaluate the magnitude of genetic variation in relative eye size, we first conducted a full-sib heritability analysis. We found that there was significant broad-sense heritability in both absolute eye height (H²=0.53) and thorax length (H²=0.39), but that the two variables were highly correlated (r=0.92). Nevertheless, we detected a smaller but highly significant heritability in the ratio of eye height to thorax length (H²=0.19). This suggests that strong selection could drive divergence in this trait. With this in mind, we have begun a selection experiment that aims to disrupt the eye size to body size relationship. We predict that if the constraints imposed by body size on eye size are substantial, selection favoring individuals with large eye height to thorax length ratios will not cause a substantial change in this ratio. In contrast, lines subjected to selection favoring small eye height to thorax length ratios should experience a reduction in relative eye size. Results from the selection experiment will be presented.