Sexual selection against natural hybrids may contribute to reinforcement in a house mouse hybrid zone (original) (raw)
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Reinforcement selection acting on the European house mouse hybrid zone
Molecular Ecology, 2011
Behavioural isolation may lead to complete speciation when partial postzygotic isolation acts in the presence of divergent-specific mate-recognition systems. These conditions exist where Mus musculus musculus and M. m. domesticus come into contact and hybridize. We studied two mate-recognition signal systems, based on urinary and salivary proteins, across a Central European portion of the mouse hybrid zone. Introgression of the genomic regions responsible for these signals: the major urinary proteins (MUPs) and androgen binding proteins (ABPs), respectively, was compared to introgression at loci assumed to be nearly neutral and those under selection against hybridization. The preference of individuals taken from across the zone regarding these signals was measured in Y mazes, and we develop a model for the analysis of the transition of such traits under reinforcement selection. The strongest assortative preferences were found in males for urine and females for ABP. Clinal analyses confirm nearly neutral introgression of an Abp locus and two loci closely linked to the Abp gene cluster, whereas two markers flanking the Mup gene region reveal unexpected introgression. Geographic change in the preference traits matches our reinforcement selection model significantly better than standard cline models. Our study confirms that behavioural barriers are important components of reproductive isolation between the house mouse subspecies.
Strong premating divergence in a unimodal hybrid zone between two subspecies of the house mouse
Journal of Evolutionary …, 2004
Although selection against hybridization is expected to generate prezygotic divergence in unimodal hybrid zones, such a pattern has been seldom described. This study aims to better understand how prezygotic mechanisms may evolve in such zones. We investigated prezygotic divergence between populations of two subspecies of mice (Mus musculus musculus and M. m. domesticus) located at the edges of their unimodal hybrid zone in Denmark, and we developed an original multiple-population choice-test design, which allows assessment of within and between subspecies variation. Our study demonstrates that a strong assortative preference characterises one of the two subspecies (musculus) and that urinary signals are involved in this subspecies recognition. Taking into account the specific genetic and geographical characteristics of the Danish hybrid zone, we discuss the influence of the above pattern on its fate and the mechanisms that could have favoured this prezygotic divergence, among which the role of recombined populations constituting the core of the zone.
Biological Journal of the Linnean Society, 2012
Hybrid zones between genetically diverged populations are widespread among animals and plants. Their dynamics usually depend on selection against admixture and dispersal of parental forms in the zone. Although indirect estimates of selection have been the target of many studies, dispersal has been neglected. In this study we carried out open field experiments to test whether males of two house mouse subspecies, Mus musculus musculus and Mus musculus domesticus, differ in their propensity to disperse and in their character of exploration. We tested wild-caught males and males of two wild-derived inbred strains. In addition, we examined reciprocal F1 crosses to test the prediction that these hybrids display intermediate behaviours. We revealed that M. m. musculus males were less hesitant to enter the experimental arena than were M. m. domesticus males, but once inside the arena their movements were more timid. F1 males differed from both parental strains, with longer latencies to enter the arena, but explored the arena in a similar fashion as the M. m. domesticus males, thus displaying transgressive behavioural phenotypes. These results contribute to our knowledge of behavioural divergence between the mouse subspecies, and add a new facet to the study of speciation.
Behavioral Ecology, 2002
Mate choice is the outcome of sexual preference for partners carrying specific signals. Thus, mating among conspecifics (homogamy) depends on the occurrence of species recognition systems. We asked what happens if populations diverge, and we investigated female sexual preference between two subspecies of the house mouse in populations from the borders of a hybrid zone ( Jutland, Denmark). We used choice tests to analyze the occurrence of recognition signals and to locate these signals in soiled bedding and urine. Our results show that populations of the two subspecies can be discriminated on the basis of urinary signals, suggesting that the latter have diverged. Additionally, these signals seem to have similar features in populations of different geographical origins, suggesting that subspecific differentiation occurs. This is the first demonstration that subspecific recognition through urinary signals occurs in the house mouse. However, while Mus musculus domesticus does not display a preference, we show that Mus musculus musculus females tend to mate with males of the same subspecies. We discuss the different factors that could explain these discrepancies between females of the two taxa: differences in signal perception, evolution at a different pace, or evolution under different selective pressures in their area of contact. Further, we propose that the divergence in male signal was at least partly initiated in allopatry and discuss different evolutionary scenario that may explain the patterns observed in Denmark and their relevance to isolation between the two taxa.
Odor preference in house mice: influences of habitat heterogeneity and chromosomal incompatibility
Behavioral Ecology, 2009
Theory predicts that when maladaptive hybridization occurs assortative mating preference should evolve. Moreover, habitat characteristics can influence quality of mates that is an important criterion in mate choice. Here we ask how chromosomal compatibility and differences in habitat quality might shape preference for odors of the opposite sex in the house mouse. Our study model is composed of 2 chromosomal races and their narrow hybrid zone that occur in habitats of different qualities. We performed 2-way choice tests during which opposite sex urine mixtures of each race were presented to mice from the 2 races and the hybrid zone. Differential investigation of the odor sources indicated both preference and that the odors differed. The results show that the 2 races carry distinct odors and, irrespective of the race they belonged to, males preferred odors of females from the race occurring in habitats of lower quality (hereafter, race B), whereas females preferred odors of males from the race occurring in habitats of better quality (hereafter, race A). Further, preference in the hybrid zone was for race B odors, which differed significantly from that displayed by the 2 races (i.e., for race A odors). The relative influences of geography, ecology, and chromosomal compatibility are discussed, thus leading us to propose that habitat differences might play the most important role in shaping signal divergence and preference in this system.
Signalling components of the house mouse mate recognition system
Behavioural Processes, 2009
Subspecies-specific mate recognition may represent significant barrier to gene flow between diverged genomes potentially leading to speciation. In the house mouse, assortative mating involves the coevolution of several signals and receptors. We compared signalling ability of bedding material, faeces, urine, saliva, salivary androgen binding proteins (ABP) and combinations of urine with saliva and urine with ABP in mate choice in two wild-derived inbred strains (one of Mus musculus musculus and one of Mus musculus domesticus origin). We observed high levels of variation in assortative preferences between the two strains and sexes. The strongest preferences were observed in M. m. musculus-derived individuals in tests where urine was present either alone or as part of a composite signal target. M. m. domesticus-derived mice displayed strain-specific preferences for faeces. Saliva was the least preferred stimulus in both strains and sexes. No effect of two-compound cues was detected. We conclude that there is divergence across both the stimulus and preference parts of the recognition system for both house mouse strains. Of the tested stimuli, those that have the capacity to carry a signal for extended periods under natural conditions (such as urine and faeces) seem to be the most important substances in strain-specific recognition.
Genetic Basis of Mating Preferences in Wild House Mice
Integrative and Comparative Biology, 1992
SYNOPSIS. This paper reviews work conducted over the last several years on the effect of genetic differences within the t-complex of wild house mice on female mating preference. Wild mice are polymorphic for a mutation within the t complex on chromosome 17. About 25% of wild mice are heterozygous (+/t) for a t-haplotype and the remainder are + / +. These t-haplotypes have a number of deleterious effects when homozygous and hence t/t individuals are rarely found in wild populations. We have examined preferences of +/+ and +/t females for males of both genotypes. We have found that +/t, but not +/+ females have strong preferences for +/+ males. These preferences can be modified by a variety of factors including estrous condition of the female (the preferences are stronger among estrous than diestrous females) and the dominance status of the male (when forced to choose, females give priority to male dominance status over t complex genotype in choosing males). The restiction of preference to +/t females indicates that genes on t haplotypes modulate these preferences. Because t haplotypes include the major histocompatibility complex (MHC) of the mouse we designed a study to ascertain whether the preferences of +/t females were associated with the MHC. Results of the study indicate that the preferences are independent of the MHC. Further work testing females carrying a partial t-haplotype (t wl8) indicates that the genes for mating preference are localized in the region of the t complex distal to the MHC. A large number of t haplotypes are found in wild mouse populations. Females that are themselves +/t when forced to choose between 2 +/t males (one carrying a haplotype that is the same as their own and one carrying a haplotype that is different) prefer males carrying t-haplotypes that differ from their own. Finally, we conclude that mating preference may only be a weak force regulating the frequency of t-mutations in wild mouse populations. The impact of mating preference on population genetics of genes within this region is muted because of the great importance of male dominance rank in determining mating patterns within interacting social groups.