Phylogenetic examination of female incorporation of ejaculate in Drosophila

Males of some invertebrate species transfer large ejaculates, and many of the substances contained therein are incorporated by females into their somatic and ovarian tissues. These incorporated substances are expected to be energetically costly for males to produce, but benefit males by enhancing their fertilization success and/or the viability of their offspring. A better understanding of the evolution and maintenance of this important reproductive strategy should come from phylogenetic examination. We therefore quantified the extent of ejaculate incorporation by females of 34 species of Drosophila. Substantive amounts of male-derived proteins were more frequently detected in female somatic tissue than in ovarian tissue. Substantive ejaculate incorporation by females was found to have arisen numerous times across the phylogeny and tended to be lineage specific in expression. The extent to which evolution of a nutritive function of the ejaculate may have been influenced by phylogenetic history in the genus Drosophila is discussed. Macroevolutionary relationships between the amount of ejaculate incorporated by females and other features of species' reproductive and life-history biology, including body size, sperm length, the formation of an insemination reaction in females, and sex-specific ages of reproductive maturity, also were examined after controlling for phylogenetic effects.