Sexual selection against natural hybrids may contribute to reinforcement in a house mouse hybrid zone

Abstract

Sexual selection may hinder gene flow across contact zones when hybrid recognition signals are discriminated against. We tested this hypothesis in a unimodal hybrid zone between Mus musculus musculus and Mus musculus domesticus where a pattern of reinforcement was described and lower hybrid fitness documented. We presented mice from the border of the hybrid zone with a choice between opposite sex urine from the same subspecies versus hybrids sampled in different locations across the zone. While no preference was evidenced in domesticus mice, musculus males discriminated in favour of musculus signals and against hybrid signals. Remarkably, the pattern of hybrid unattractiveness did not vary across the hybrid zone. Moreover, allopatric populations tested in the same conditions did not discriminate against hybrid signals, indicating character displacement for signal perception or preference. Finally, habituation-discrimination tests assessing similarities between signals pointed out that hybrid signals differed from the parental ones. Overall, our results suggest that perception of hybrids as unattractive has evolved in border populations of musculus after the secondary contact with domesticus. We discuss the mechanisms involved in hybrid unattractiveness, and the potential impact of asymmetric sexual selection on the hybrid zone dynamics and gene flow between the two subspecies.

Testing models of speciation from genome sequences: divergence and asymmetric admixture in Island South‐East Asian Sus species during the Plio‐Pleistocene climatic fluctuations

“…Latour et al . ). Further research on the ecology and the behaviour of the Java warty pig is needed to better interpret these results, especially given its endangered status.…”

Maternal–foetal genomic conflict and speciation: no evidence for hybrid placental dysplasia in crosses between two house mouse subspecies

“…Reduced male fertility has also been observed in wild mice in the hybrid zone (Albrechtová et al ., ; Turner et al ., ). Furthermore, partial hybrid female sterility (Britton‐Davidian et al ., ) and the reinforcement of mating‐recognition systems (Smadja & Ganem, ; Vošlajerová Bímová et al ., ; Latour et al ., ) might contribute to reproductive isolation between these two subspecies. Interestingly, some part of the hybrid zone dynamics was suggested to be affected by genetic conflict (Macholán et al ., ), but the mechanism of this conflict remains unknown.…”

Molecular heterogeneity in major urinary proteins of Mus musculus subspecies: potential candidates involved in speciation

“…Hybrids derived from the two subspecies have reduced fitness compared to non-hybrids161718, and theory predicts the evolution of assortative mating in the hybrid zone as a response to this selection against hybridisation (a process called reinforcement1920). Several studies, involving classical laboratory two-way choice tests, have consistently pointed out assortative mate preference in both wild derived and wild trapped populations from the border of the hybrid zone of the two subspecies1221222324252627, but not in their allopatric counterparts12132223242627. This is a pattern expected under a reinforcement scenario.…”