EVOLUTION: Conflict Leads to Speciation

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Science  29 Sep 2000:
Vol. 289, Issue 5488, pp. 2241b

The role of sexual selection, in the form of mate choice by females, in animal speciation is well established. Arnqvist et al. now show that post-mating sexual conflict also plays a part, at least in insects. Conflict occurs when females mate with multiple males (polyandry), giving rise to sperm competition or ‘cryptic' female choice. Under these conditions the evolutionary interests of males and females can differ, leading to antagonistic coevolution between the reproductive physiologies of the two sexes. This, in turn, might lead to rapid reproductive isolation between allopatric populations and hence a higher rate of speciation.

To test this idea, Arnqvist et al. performed a meta-analysis using published literature, reference databases, and the World Wide Web, covering insects in five different orders. They compared polyandrous groups with other groups in which females mate only once, and found that speciation rates, as measured by species richness in clades of known phylogeny, was up to four times higher where sexual conflict was present. This estimate does not include extinction rates, which might be expected to be higher in groups with sexual conflict; thus, the true effect of sexual conflict may turn out to be even greater. — AMS

Acknowledgments

Proc. Natl. Acad. Sci. U.S.A. 97, 10460 (2000).

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