Evolution of external female genital mutilation: why do males harm their mates?

Evolution of external female genital mutilation: why do males harm their mates? Pierick Mouginot, Gabriele Uhl, Lutz Fromhage. Royal Society Open Science, November 2017. https://doi.org/10.1098/rsos.171195

Abstract: Sperm competition may select for male reproductive traits that influence female mating or oviposition rate. These traits may induce fitness costs to the female; however, they may be costly for the males as well as any decrease in female fitness also affects male fitness. Male adaptations to sperm competition manipulate females by altering not only female behaviour or physiology, but also female morphology. In orb-weaving spiders, mating may entail mutilation of external structures of the female genitalia, which prevents genital coupling with subsequent males. Here, we present a game theoretical model showing that external female genital mutilation is favoured even under relatively high costs of mutilation, and that it is favoured by a high number of mate encounters per female and last-male sperm precedence.

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Males may evolve traits that shift the remating or oviposition rate of the female from the female’s optimum towards their own due to selection on competitive fertilization success [1,2]. Defensive adaptations to sperm competition include mate guarding, copulatory plugs,manipulative seminal fluids and internal genital damage. These adaptations can manipulate the female by altering her behaviour or physiology, but also her genital anatomy [3]. Examples of male-inflicted damages to female genitalia have been documented in numerous taxa, especially among arthropods [4,5]. Most of these genital damages are inflicted internally by the male intromittent organ, and it is debated how these harmful traits have evolved [6–8].

Recently, it has been described that males inflict external damage to the female genitalia in two species of orb-weaving spiders as a defensive adaptation to sperm competition.

Check also Male reproductive suppression: not a social affair. Z. Valentina Zizzari, Andrea Jessen, and Joris M. Koene. Current Zoology, Volume 63, Issue 5, 1 October 2017, Pages 573–579,
http://www.bipartisanalliance.com/2017/09/homosexual-acts-may-help-impair.html