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. 2008 Oct 8;3(10):e3328.
doi: 10.1371/journal.pone.0003328.

Genetic dissimilarity between mates, but not male heterozygosity, influences divorce in schistosomes

Sophie Beltran  1 , Frank Cézilly, Jérôme Boissier
Affiliations

Genetic dissimilarity between mates, but not male heterozygosity, influences divorce in schistosomes

Sophie Beltran et al. PLoS One. .

Abstract

Background: Correlational studies strongly suggest that both genetic similarity and heterozygosity can influence female mate choice. However, the influence of each variable has usually been tested independently, although similarity and heterozygosity might be correlated. We experimentally determined the relative influence of genetic similarity and heterozygosity in divorce and re-mating in the monogamous endoparasite Schistosoma mansoni.

Methodology/principal findings: We performed sequential infections of vertebrate hosts with controlled larval populations of parasites, where sex and individual genetic diversity and similarity were predetermined before infection. Divorce rate increased significantly when females were given the opportunity to increase genetic dissimilarity through re-mating with a new partner, independently of the intensity of male-male competition. We found however no evidence for females attempting to maximize the level of heterozygosity of their reproductive partner through divorce.

Conclusions/significance: Female preference for genetically dissimilar males should result in more heterozygous offspring. Because genetic heterozygosity might partly determine the ability of parasites to counter host resistance, adaptive divorce could be an important factor in the evolutionary arms race between schistosomes and their hosts.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. A schistosome pair, with the thin female located in the male gynaecophorical canal.
Figure 2
Figure 2. Differences in mean divorce rate corrected by numerical ‘pressure’ (±SE), according to which sex is given opportunities to divorce.
The numerical ‘pressure’ is measured as the number of individuals introduced during the second infection divided by the number of individual of the same sex introduced on the first one.
Figure 3
Figure 3. Influence of genetic dissimilarity between mates and male heterozygosity on divorce rate corrected by male-male competition in schistosomes.
Genetic dissimilarity was estimated using the r coefficient of Wang and heterozygosity was calculated for each male clone as the number of heterozygous loci divided by the total number of loci. We defined ΔH as the difference in overall heterozygosity between the newcomer male and the first male, and ΔD as the difference in genetic dissimilarity to the female between the first male and the newcomer male (Table 1). When positive, ΔH and ΔD indicate increased heterozygosity in females' progeny. Each colour represents a different female clone. The intensity of male-male competition is measured as the number of individuals introduced during the second infection divided by the number of individual of the same sex introduced on the first one. A total of 528 pairs was analysed.
See this image and copyright information in PMC

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