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1 June 2009 Intersexual Arms Race? Genital Coevolution in Nephilid Spiders (Araneae, Nephilidae)
Matjaž Kuntner, Jonathan A. Coddington, Jutta M. Schneider
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Genital morphology is informative phylogenetically and strongly selected sexually. We use a recent species-level phylogeny of nephilid spiders to synthesize phylogenetic patterns in nephilid genital evolution that document generalized conflict between male and female interests. Specifically, we test the intersexual coevolution hypothesis by defining gender-specific indices of genital complexity that summarize all relevant and phylogenetically informative traits. We then use independent contrasts to show that male and female genital complexity indices correlate significantly and positively across the phylogeny rather than among sympatric sister species, as predicted by reproductive character displacement. In effect, as females respond to selection for fecundity-driven fitness via giantism and polyandry (perhaps responding to male-biased effective sex ratios), male mechanisms evolve to monopolize females (male monogamy) via opportunistic mating, pre- and postcopulatory mate guarding, and/or plugging of female genitalia to exclude subsequent suitors. In males morphological symptoms of these phenomena range from self-mutilated genitalia to total castration. Although the results are compatible with both recently favored sexual selection hypotheses, sexually antagonistic coevolution, and cryptic female choice, the evidence of strong intersexual conflict and genitalic damage in both sexes is more easily explained as sexually antagonistic coevolution due to an evolutionary arms race.

© 2009 The Society for the Study of Evolution.
Matjaž Kuntner, Jonathan A. Coddington, and Jutta M. Schneider "Intersexual Arms Race? Genital Coevolution in Nephilid Spiders (Araneae, Nephilidae)," Evolution 63(6), 1451-1463, (1 June 2009).
Received: 8 January 2008; Accepted: 1 January 2009; Published: 1 June 2009

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cryptic female choice
morphological complexity
Reproductive character displacement
sexual conflict
sexually antagonistic coevolution
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