The Evolutionary Genetics of Sexual Size Dimorphism in a Seed-Feeding Beetle

This study will test theoretical predictions about how genetic relationships between traits change in response to natural selection. More specifically, it will examine how genetic relationships between traits expressed differently in males and females change in response to differing selection on males and females. Using an insect species that exhibits little sexual dimorphism, the experiments will impose artificial selection on the body size of either one sex at a time or both sexes at once (simulating patterns of natural selection often observed in nature) and examine (a) correlated evolutionary responses in the alternate (unselected) sex, (b) correlated responses of other non-selected traits (e.g., reproductive traits), and (c) the evolution of genetic variances and covariances. The experiments will also impose selection on female fecundity, and male and female development time. This will test the hypotheses that selection for increased fecundity and selection for short development time influence the evolution of sexual size dimorphism in a manner predicted by theory. Although many studies have examined how traits are genetically related to each other, few previous studies have examined how these genetic relationships change when traits are subject to natural selection. Yet natural selection is ubiquitous in nature; and human beings impose natural selection on organisms in agricultural animal and plant breeding programs, during application of pesticides to agricultural fields, in the use of antibiotics, and whenever natural biological events are manipulated. Understanding how genetic relationships among traits change as we impose natural selection on these traits is critical to understanding the long-term evolutionary responses of populations to this selection.