title: Mechanisms underlying the sperm quality advantage in Drosophila melanogaster.
abstract: Contrary to early predictions of sperm competition theory, postcopulatory sexual selection favoring increased investment per sperm (e.g., sperm size, sperm quality) has been demonstrated in numerous organisms. We empirically demonstrate for Drosophila melanogaster that both sperm quality and sperm quantity independently contribute to competitive male fertilization success. In addition to these independent effects, there was a significant interaction between sperm quality and quantity that suggests an internal positive reinforcement on selection for sperm quality, with selection predicted to intensify as investment per sperm increases and the number of sperm competing declines. The mechanism underlying the sperm quality advantage is elucidated through examination of the relationship between female sperm-storage organ morphology and the differential organization of different length sperm within the organ. Our results exemplify that primary sex cells can bear secondary sexual straits.
authors.affiliation: Department of Biology, Syracuse University, 108 College Place, Syracuse, New York 13244-1270, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Pattarini
authors.forename: William T
authors.initials: WT
authors.lastname: Starmer
authors.forename: Adam
authors.initials: A
authors.lastname: Bjork
authors.forename: Scott
authors.initials: S
authors.lastname: Pitnick
mesh_terms: D000818:Animals; D048429:Cell Size; D004331:Drosophila melanogaster / Q000502:physiology*; D005260:Female; D005306:Fertilization; D008297:Male; D013076:Sperm Count; D013082:Sperm Tail; D013094:Spermatozoa / Q000166:cytology / Q000502:physiology*