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

Beltran S, Cézilly F, Boissier J - PLoS ONE (2008)

Bottom Line: 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.Female preference for genetically dissimilar males should result in more heterozygous offspring.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Biologie et d'Ecologie Tropicale et Méditerranéenne, UMR 5244 CNRS-EPHE-UPVD, Université de Perpignan, Perpignan, France.

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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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 [20] 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.
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pone-0003328-g003: 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 [20] 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.

Mentions: Overall, five different female clones and nine different male clones were used in the experiments (Table 1). ΔD varied between −0.60 to 0.88, while ΔH varied between −42% to +33%. Divorce rate, corrected by the intensity of male-male competition, ranged from 0 to 29% (Fig. 3), and differed significantly between tests (logistic regression, χ2 = 98.11, d.f. = 11, P<0.0001). Results from a logistic regression indicated that genetic dissimilarity had the larger influence on divorce rate (χ2 = 24.79, d.f. = 1, p<0.0001, whereas the intensity of male-male competition (χ2 = 5.44, d.f. = 1, p = 0.020) and female clone (χ2 = 10.16, d.f. = 4, p = 0.038) had only a marginal effect. By contrast, male heterozygosity had no significant influence on divorce rate (χ2 = 0.64, d.f. = 1, p = 0.424). Overall, females were more likely to switch mates when the newcomer male was more dissimilar to themselves than their first mate. When ΔD was positive, the mean divorce frequency corrected by the intensity of male-male competition (20.2%±4.3%) was about ten times higher than for negative values of ΔD (2.11%±0.9%).


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

Beltran S, Cézilly F, Boissier J - PLoS ONE (2008)

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 [20] 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.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2553268&req=5

pone-0003328-g003: 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 [20] 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.
Mentions: Overall, five different female clones and nine different male clones were used in the experiments (Table 1). ΔD varied between −0.60 to 0.88, while ΔH varied between −42% to +33%. Divorce rate, corrected by the intensity of male-male competition, ranged from 0 to 29% (Fig. 3), and differed significantly between tests (logistic regression, χ2 = 98.11, d.f. = 11, P<0.0001). Results from a logistic regression indicated that genetic dissimilarity had the larger influence on divorce rate (χ2 = 24.79, d.f. = 1, p<0.0001, whereas the intensity of male-male competition (χ2 = 5.44, d.f. = 1, p = 0.020) and female clone (χ2 = 10.16, d.f. = 4, p = 0.038) had only a marginal effect. By contrast, male heterozygosity had no significant influence on divorce rate (χ2 = 0.64, d.f. = 1, p = 0.424). Overall, females were more likely to switch mates when the newcomer male was more dissimilar to themselves than their first mate. When ΔD was positive, the mean divorce frequency corrected by the intensity of male-male competition (20.2%±4.3%) was about ten times higher than for negative values of ΔD (2.11%±0.9%).

Bottom Line: 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.Female preference for genetically dissimilar males should result in more heterozygous offspring.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Biologie et d'Ecologie Tropicale et Méditerranéenne, UMR 5244 CNRS-EPHE-UPVD, Université de Perpignan, Perpignan, France.

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.

Show MeSH
Related in: MedlinePlus