Patterns of reproductive isolation within and between two Lygaeus species characterized by sexual conflicts over mating
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Theory suggests that, under some circumstances, sexual conflict over mating can lead to divergent sexually antagonistic coevolution among populations for traits associated with mating, and that this can promote reproductive isolation and hence speciation. However, sexual conflict over mating may also select for traits (e.g. male willingness to mate) that enhance gene flow between populations, limiting population divergence. In the present study, we compare pre- and post-mating isolation within and between two species characterized by male-female conflict over mating rate. We quantify sexual isolation among five populations of the seed bug Lygaeus equestris collected from Italy and Sweden, and two replicates of a population of the sister-species Lygaeus simulans, also collected from Italy. We find no evidence of reproductive isolation amongst populations of L. equestris, suggesting that sexual conflict over mating has not led to population divergence in relevant mating traits in L. equestris. However, there was strong asymmetric pre-mating isolation between L. equestris and L. simulans: male L. simulans were able to mate successfully with female L. equestris, whereas male L. equestris were largely unable to mate with female L. simulans. We found little evidence for strong post-mating isolation between the two species, however, with hybrid F2 offspring being produced. Our results suggest that sexual conflict over mating has not led to population divergence, and indeed perhaps supports the contrary theoretical prediction that male willingness to mate may retard speciation by promoting gene flow.
Evans , G M V , Nowlan , T & Shuker , D M 2015 , ' Patterns of reproductive isolation within and between two Lygaeus species characterized by sexual conflicts over mating ' Biological Journal of the Linnean Society , vol. 116 , no. 4 , pp. 890-901 . DOI: 10.1111/bij.12639
Biological Journal of the Linnean Society
This is the peer reviewed version of the following article: Patterns of reproductive isolation within and between two Lygaeus species characterized by sexual conflicts over mating Evans, G. M. V., Nowlan, T. & Shuker, D. M. 2015 In : Biological Journal of the Linnean Society., which has been published in final form at http://dx.doi.org/10.1111/bij.12639. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
DescriptionThe authors are very grateful to NERC for funding (a Studentship to GMVE and an Advanced Fellowship to DMS).
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