Genetic conflict outweighs heterogametic incompatibility in the mouse hybrid zone?

<p>Abstract</p> <p>Background</p> <p>The <it>Mus musculus musculus/M. m. domesticus </it>contact zone in Europe is characterised by sharp frequency discontinuities for sex chromosome markers at the centre of wider clines in allozyme frequencies.</p> <p>Results</p> <p>We identify a triangular area (approximately 330 km²) where the <it>musculus </it>Y chromosome introgresses across this front for up to 22 km into <it>domesticus </it>territory. Introgression of the Y chromosome is accompanied by a perturbation of the census sex ratio: the sex ratio is significantly female biased in <it>musculus </it>localities and <it>domesticus </it>localities lacking Y chromosome introgression. In contrast, where the <it>musculus </it>Y is detected in <it>domesticus </it>localities, the sex ratio is close to parity, and significantly different from both classes of female biased localities. The geographic position of an abrupt cline in an X chromosome marker, and autosomal clines centred on the same position, seem unaffected by the <it>musculus </it>Y introgression.</p> <p>Conclusion</p> <p>We conclude that sex ratio distortion is playing a role in the geographic separation of speciation genes in this section of the mouse hybrid zone. We suggest that clines for genes involved in sex-ratio distortion have escaped from the centre of the mouse hybrid zone, causing a decay in the barrier to gene flow between the two house mouse taxa.</p

Intensity of infection with intracellular Eimeria spp. and pinworms is reduced in hybrid mice compared to parental subspecies

Genetic diversity in animal immune systems is usually beneficial. In hybrid recombinants, this is less clear, as the immune system could also be impacted by genetic conflicts. In the European house mouse hybrid zone, the long‐standing impression that hybrid mice are more highly parasitized and less fit than parentals persists despite the findings of recent studies. Working across a novel transect, we assessed infections by intracellular protozoans, Eimeria spp., and infections by extracellular macroparasites, pinworms. For Eimeria, we found lower intensities in hybrid hosts than in parental mice but no evidence of lowered probability of infection or increased mortality in the centre of the hybrid zone. This means ecological factors are very unlikely to be responsible for the reduced load of infected hybrids. Focusing on parasite intensity (load in infected hosts), we also corroborated reduced pinworm loads reported for hybrid mice in previous studies. We conclude that intensity of diverse parasites, including the previously unstudied Eimeria, is reduced in hybrid mice compared to parental subspecies. We suggest caution in extrapolating this to differences in hybrid host fitness in the absence of, for example, evidence for a link between parasitemia and health.Peer Reviewe

European mammalogy 2003

Program, abstracts and list of participants of the 4th European Congress of Mammalogy