Equal fitness among alternative mating strategies in a harem polygynous insect

Alternative mating strategies are widespread among animal taxa, with strategies controlled by a genetic polymorphism (Mendelian strategy) being rarer in nature than condition-dependent developmental strategies. Mendelian strategies are predicted to have equal average fitnesses and the proportion of offspring produced by a strategy should equal the equilibrium proportion of individuals representing the strategy in a population. Developmental strategies are not expected to produce offspring in equilibrium proportions; however, whether the alternative phenotypes should have equal average fitness is debated. The Wellington tree wētā ( Hemideina crassidens ) (Orthoptera: Anostostomatidae) is a harem polygynous insect in which intense sexual competition has favoured the evolution of three alternative mating strategies that differ in weapon size and the ability to fight for control of harems. Here, we use molecular genotyping to test the hypothesis that the alternative strategies in this species are maintained by having equal relative fitness and that morphs produce offspring in equilibrium proportions. As expected, the average relative fitness of the three strategies did not significantly differ and the proportion of offspring produced by each morph is equal to the frequency of that morph in the population. Our results support the hypothesis that the alternative male morphs in H. crassidens represent Mendelian strategies.

Pair bonds, reproductive success, and rise of alternate mating strategies in a social carnivore

Monogamy is commonly observed across a wide variety of species and taxa and arises when young are altricial, parental investment in young is high, and mate monopolization is generally not possible. In such species, pairs may bond for multiple breeding seasons while successfully rearing young. Individuals, however, may attempt to bypass the dominant mating strategy particularly when breeding opportunities are limited. Currently, we do not know how pair bond duration affects the efficacy of alternative mating strategies in populations with a monogamous mating system. Additionally, inferences about pair bond effects on reproductive success (i.e., both clutch size and recruitment) are largely limited to long-lived birds and little is known about effects on mammalian cooperative breeders. I used genetic sampling and pedigrees to examine the effects of pair bond duration on reproductive success (i.e., litter size, recruitment) and mating strategies in a population of gray wolves (Canis lupus) in Idaho, USA. There was a positive, marginally significant relationship between pair bond duration and apparent survival of offspring. Increased pair bond duration was also associated with a dampening in the prevalence of other alternative mating strategies such as sneaker males and polygamy. The selective advantage of alternative mating strategies is a combination of population, group (for applicable species), individual, and social influences such as pair bonds. The distribution of pair bonds in a monogamous population affects the selective advantage, and hence frequency, of various mating strategies observed.