Meeting Abstract
While reproductive traits are known to be some of nature’s most rapidly evolving traits, investigations of this rapid evolution have traditionally focused on male reproductive traits. Females have been commonly viewed as passive participants in sexual reproduction, despite increasing evidence that female genitalia and proteins evolve at rates comparable to those documented in males. To better understand the rapid evolution of female reproductive traits, and how such rapid evolution may contribute to reproductive isolation, we studied evolutionary divergence in female reproductive traits of the Cabbage White butterfly, Pieris rapae. In butterflies and moths, females possess a unique reproductive organ, called the bursa copulatrix, which functions to digest the male spermatophore. Crosses between recently isolated subspecies indicate a potential reproductive barrier involving reduced spermatophore digestion rates in hetero-subspecific crosses. These results imply that traits involved in spermatophore digestion may have diverged between these two subspecies. Expression analyses of male and female proteins involved in bursa-spermatophore interactions indicate that proteins specific to the spermatophore remain constant in expression between the subspecies. In contrast, the female proteases that digest the spermatophore differ dramatically in their expression. Additionally, we observed a unique co-option event in one subspecies, where a protease normally expressed during the larval stage was also expressed in the bursa. Taken together, these results indicate that female reproductive traits may, in some species, be more evolutionarily dynamic than male traits. Our work thus motivates more careful study of female reproductive traits and their role in the rapid evolution of reproductive barriers.
