Sexual Activity and Reproductive Isolation Between Age-specific Selected Populations of Seed Beetle

We evaluated the degree of reproductive isolation between laboratory populations of the seed beetle (Acanthoscelides obtectus) selected to reproduce early (E) or late (L) in life, where different levels of sexual activity and sexual discrimination have been detected. We found a significant level of behavioral isolation among populations within the E selection regime in which beetles showed enhanced early-life fitness traits and low sexual activity. In contrast, substantially higher levels of sexual activity and an indiscriminate mating system inhibited rather than promoted pre-zygotic isolation between the L populations. Our results indicate that the study of sexual activity levels may be crucial for understanding the first steps in the pre-zygotic isolation among allopatric populations subjected to uniform selection.