title: Rapid diversification of sperm precedence traits and processes among three sibling Drosophila species.
abstract: Postcopulatory sexual selection is credited with driving rapid evolutionary diversification of reproductive traits and the formation of reproductive isolating barriers between species. This judgment, however, has largely been inferred rather than demonstrated due to general lack of knowledge about processes and traits underlying variation in competitive fertilization success. Here, we resolved processes determining sperm fate in twice-mated females, using transgenic Drosophila simulans and Drosophila mauritiana populations with fluorescently labeled sperm heads. Comparisons among these two species and Drosophila melanogaster revealed a shared motif in the mechanisms of sperm precedence, with postcopulatory sexual selection potentially occurring during any of the three discrete stages: (1) insemination; (2) sperm storage; and (3) sperm use for fertilization, and involving four distinct phenomena: (1) sperm transfer; (2) sperm displacement; (3) sperm ejection; and (4) sperm selection for fertilizations. Yet, underlying the qualitative similarities were significant quantitative differences in nearly every relevant character and process. We evaluate these species differences in light of concurrent investigations of within-population variation in competitive fertilization success and postmating/prezygotic reproductive isolation in hybrid matings between species to forge an understanding of the relationship between microevolutionary processes and macroevolutionary patterns as pertains to postcopulatory sexual selection in this group.
authors.affiliation: Department of Biology, Syracuse University, Syracuse, New York 13244, USA.
authors.forename: Mollie K
authors.initials: MK
authors.lastname: Manier
authors.forename: John M
authors.initials: JM
authors.lastname: Belote
authors.forename: Kirstin S
authors.initials: KS
authors.lastname: Berben
authors.forename: Stefan
authors.initials: S
authors.lastname: Lüpold
authors.forename: Outi
authors.initials: O
authors.lastname: Ala-Honkola
authors.forename: William F
authors.initials: WF
authors.lastname: Collins
authors.forename: Scott
authors.initials: S
authors.lastname: Pitnick
mesh_terms: D000818:Animals; D004330:Drosophila / Q000145:classification* / Q000235:genetics / Q000502:physiology*; D004331:Drosophila melanogaster / Q000235:genetics / Q000502:physiology; D005260:Female; D005306:Fertilization; D049810:Genetic Speciation; D008297:Male; D012726:Sexual Behavior, Animal; D013094:Spermatozoa / Q000502:physiology*
keywords: Cryptic female choice; fertilization; postcopulatory sexual selection; reproductive isolation; sperm competition; sperm storage