Males and Females Contribute Unequally to Offspring Genetic Diversity in the Polygynandrous Mating System of Wild Boar

The maintenance of genetic diversity across generations depends on both the number of reproducing males and females. Variance in reproductive success, multiple paternity and litter size can all affect the relative contributions of male and female parents to genetic variation of progeny. The mating system of the wild boar (Sus scrofa) has been described as polygynous, although evidence of multiple paternity in litters has been found. Using 14 microsatellite markers, we evaluated the contribution of males and females to genetic variation in the next generation in independent wild boar populations from the Iberian Peninsula and Hungary. Genetic contributions of males and females were obtained by distinguishing the paternal and maternal genetic component inherited by the progeny. We found that the paternally inherited genetic component of progeny was more diverse than the maternally inherited component. Simulations showed that this finding might be due to a sampling bias. However, after controlling for the bias by fitting both the genetic diversity in the adult population and the number of reproductive individuals in the models, paternally inherited genotypes remained more diverse than those inherited maternally. Our results suggest new insights into how promiscuous mating systems can help maintain genetic variation

The contribution of males and females to offspring genetic diversity.

<p>Paternal genotypes inference performed by: a) Method 1; b) Method 2; c) Method 3. Results are shown separately for each population. WIP: Western Iberian Peninsula; AZA: Azagala; SAM: Santa Amalia; HUN: Hungary. Figure shows means and standard errors of observed values.</p

Fixed effects of a LMM fitted using MCMC in which we compared the genetic diversity in paternally and maternally transmitted genotypes.

<p>Table shows the posterior estimate of the effects, the 95% credibility interval and the probability that the null hypothesis is true (effect = 0). Parental allele assignment performed by: a) Method 1. b) Method 2. c) Method 3. Maternal genotype as reference.</p><p>Fixed effects of a LMM fitted using MCMC in which we compared the genetic diversity in paternally and maternally transmitted genotypes.</p

Simulation results for the initial population.

<p>Black solid line: relationship between the number of sampled females (X axis) and the diversity of paternally transmitted genotypes. Black dashed line: relationship between the number of sampled females (X axis) and the diversity of maternally transmitted genotypes. Black dotted line: relationship between the estimated number of mates (X axis) and the diversity of paternally transmitted genotypes. Grey solid line: relationship between the number of sampled females (X axis) and the estimated number of sampled reproductive males (mates; note that these values were used as X axis to construct the black dotted line). Grey dashed line: equality between the number of sampled females (X axis) and the estimated number of reproducing males.</p

Fixed effects of a LMM fitted using MCMC in which we compared the genetic diversity of paternally and maternally transmitted genotypes after controlling for the genetic diversity in adults and the number of reproductive individuals.

<p>Table shows the posterior estimate of the effects, the 95% credibility interval and the probability that the null hypothesis is true (effect = 0). a) Method 1. b) Method 2. c) Method 3. When Sex factor was coded as “males” dependent variable was genetic diversity of paternal genotypes, Genetic diversity in adults referred to genetic diversity in the random sample of males and Number of reproductive individuals referred to number of inferred fathers. When Sex factor was coded as “females”, dependent variable was genetic diversity of maternal genotypes, Genetic diversity in adults referred to genetic diversity in pregnant females and Number of reproductive individuals referred to number mothers. Females were used as reference for sex factor.</p><p>Fixed effects of a LMM fitted using MCMC in which we compared the genetic diversity of paternally and maternally transmitted genotypes after controlling for the genetic diversity in adults and the number of reproductive individuals.</p

Mating characteristics of populations.

<p>N_mothers: number of sampled mothers. N_fathers: number of inferred fathers. MP rate: multiple paternity rate. M_mothers: mean litter size. M_fathers: mean reproductive success of fathers. V_mothers: variance in litter size. V_fathers: variance in father reproductive success. Data for mothers were directly estimated from the sampled pregnant females. Data for fathers were estimated using Colony analyses of maternal and foetus genotypes.</p><p>Mating characteristics of populations.</p

Simulation results after varying <i>V_males</i>, <i>MP</i>, <i>LS</i> and <i>V_females</i>.

<p>The relative diversity of maternally and paternally transmitted genotypes (genetic diversity of maternal genotypes - genetic diversity of paternal genotypes; black lines) and the estimated number of sampled reproductive males (mates; grey lines) for different female sampling intensities are shown. a) Three populations that differ in <i>V_males</i>. b) Three populations that differ in <i>MP</i>. c) Three populations that differ in <i>LS</i>. d) Three populations that differ in <i>V_females</i>. In all graphs, the solid line represents the initial population, the dotted line represents the <i>below</i> population (i.e. where the adjusted parameter is reduced relative to the initial conditions) and the dashed line represents the <i>above</i> population (parameter is increased relative to initial conditions). The thin horizontal black dashed line represents equal genetic diversity in maternally and paternally transmitted genotypes. The thin diagonal grey dotted line represents equality between the estimated number of reproducing males and the number of sampled females.</p