title: No evidence for external genital morphology affecting cryptic female choice and reproductive isolation in Drosophila.
abstract: Genitalia are one of the most rapidly diverging morphological features in animals. The evolution of genital morphology is proposed to be driven by sexual selection via cryptic female choice, whereby a female selectively uptakes and uses a particular male's sperm on the basis of male genital morphology. The resulting shifts in genital morphology within a species can lead to divergence in genitalia between species, and consequently to reproductive isolation and speciation. Although this conceptual framework is supported by correlative data, there is little direct empirical evidence. Here, we used a microdissection laser to alter the morphology of the external male genitalia in Drosophila, a widely used genetic model for both genital shape and cryptic female choice. We evaluate the effect of precision alterations to lobe morphology on both interspecific and intraspecific mating, and demonstrate experimentally that the male genital lobes do not affect copulation duration or cryptic female choice, contrary to long-standing assumptions regarding the role of the lobes in this model system. Rather, we demonstrate that the lobes are essential for copulation to occur. Moreover, slight alterations to the lobes significantly reduced copulatory success only in competitive environments, identifying precopulatory sexual selection as a potential contributing force behind genital diversification.
authors.affiliation: The University of Western Ontario, Department of Biology, London, Ontario, N6A 5B7, Canada.
authors.forename: Hélène
authors.initials: H
authors.lastname: LeVasseur-Viens
authors.affiliation: The University of Cincinnati, Department of Biological Sciences, Cincinnati, Ohio, 45221.
authors.forename: Michal
authors.initials: M
authors.lastname: Polak
authors.affiliation: The University of Western Ontario, Department of Biology, London, Ontario, N6A 5B7, Canada. amoehrin@uwo.ca.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Moehring
mesh_terms: D000818:Animals; D002755:Choice Behavior; D004330:Drosophila / Q000033:anatomy & histology* / Q000502:physiology*; D005260:Female; D005837:Genitalia, Male / Q000033:anatomy & histology; D008297:Male; D052586:Mating Preference, Animal; D060047:Reproductive Isolation; D013045:Species Specificity
keywords: Drosophila mauritiana; Drosophila simulans; genital coupling; posterior lobe; sexual selection