Orthology, function and evolution of accessory gland proteins in the Drosophila repleta group.

The accessory gland proteins (Acps) of Drosophila have become a model for the study of reproductive protein evolution. A major step in the study of Acps is to identify biological causes and consequences of the observed patterns of molecular evolution by comparing species groups with different biology. Here we characterize the Acp complement of Drosophila mayaguana, a repleta group representative. Species of this group show important differences in ecology and reproduction as compared to other Drosophila. Our results show that the extremely high rates of Acp evolution previously found are likely to be ubiquitous among species of the repleta group. These evolutionary rates are considerably higher than the ones observed in other Drosophila groups' Acps. This disparity, however, is not accompanied by major differences in the estimated number of Acps or in the functional categories represented as previously suggested. Among the genes expressed in accessory glands of D. mayaguana almost half are likely products of recent duplications. This allowed us to test predictions of the neofunctionalization model for gene duplication and paralog evolution in a more or less constrained timescale. We found that positive selection is a strong force in the early divergence of these gene pairs.