Mother guarding: how offspring may influence the extra-pair behaviour of their parents

In this paper we propose a novel form of social control of mate choice. Through mother guarding, offspring can help in protecting the paternity of their father by preventing their mother from engaging in extra-pair matings. We present a model that predicts the circumstances under which mothers should be selected to seek or avoid extra-pair matings, and existing offspring should be selected to prevent or promote such matings. In its simplest form, our model shows that offspring are selected to mother guard as long as the viability of extra-pair young is less than twice that of within-pair young; when the relative viability is greater, offspring are selected to promote extra-pair mating by their mother. If the existing offspring are not necessarily sired by their mother's social mate, then the potential for conflict is further reduced. We also consider whether offspring have an interest in the extra-pair reproduction of their fathers. We show that when the costs of the father's infidelity to the mother's brood are high, existing offspring are selected to prevent extra-pair mating by their father; when such costs are low, offspring are selected to promote extra-pair mating by their father. In principle, our model applies to all species where offspring show delayed dispersal and where breeding pairs raise multiple broods or litters. This situation exists in, but is not limited to, the majority of cooperatively breeding species. The significance of this model with regard to our current understanding of the evolution of extra-pair behaviour in such species is discussed

Social structure influences extra-pair paternity in socially monogamous mammals

Using the genetic estimates of paternity available for 22 species of socially monogamous mammals, we investigated the impact of the social structure and of the type of pair bonding on the interspecific variations of extra-pair paternity rates. To this purpose, we classified species in three categories of social structure—solitary, pair or family-living species—and in two categories of pair bonding—intermittent or continuous. We show that interspecific variations of extra-pair paternity rates are better explained by the social structure than by the type of pair bonding. Species with intermittent and continuous pair bonding present similar rates of extra-pair paternity, while solitary and family-living species present higher extra-pair paternity rates than pair-living species. This can be explained by both higher male–male competition and higher female mate choice opportunities in solitary and family-living species than in pair-living species

Linking mating preferences to sexually selected traits and offspring viability: good versus complementary genes hypotheses

Indirect fitness benefits hypotheses suggest that offspring of preferred mates should exhibit greater survival or reproductive success. For example, good genes hypotheses propose that female mating preferences are mediated by secondary sexual traits because they honestly reflect the ability to pass on genes that will enhance offspring survival or reproduction. Conversely, complementary genes hypotheses propose that mating preferences are mediated by complementary genes because they enhance offspring viability. While these two research traditions are not strict alternatives and both may operate simultaneously, they have never been tested together. Here we explore the multiple potential underlying factors influencing mating preference ev

Choosy males in Jamaican field crickets

Male mate choice is an often neglected aspect of sexual selection studies. While theory predicts that females should exhibit mate choice due to their comparatively greater investment in gametes, males may also exhibit mate choice for a variety of reasons, including seeking mates with greater fecundity. Furthermore, males may exhibit discriminant or indiscriminate mate choice as a function of their own intrinsic characteristics, such as body size or condition. Here we experimentally evaluated male Jamaican field cricket, Gryllus assimilis, mating preferences using randomly selected females and determined how both male and female morphology (body size and residual mass) and male signalling behaviour influence male mate preference. Results show that male crickets exhibit mating preferences, with larger males tending to exhibit more consistent mate preferences than smaller males. Contrary to predictions, males did not prefer larger or relatively heavier females, suggesting that males may not be basing their choosiness on these proxy measures of female fecundity. Our findings highlight the need for continued research on male mate ch

What is driving male mate preference evolution in Jamaican field crickets?

Male mating preferences are often a neglected aspect of studies on sexual selection. Male mating preferences may evolve if they provide males with direct-fitness benefits such as increased opportunity to fertilize more eggs or indirect-fitness benefits such as enhanced offspring survival. We tested these ideas using Jamaican field crickets, Gryllus assimilis, previously shown to exhibit male mating preferences. We randomly mated males to either their preferred or non-preferred potential mates and then asked whether mating treatment influenced egg oviposition or offspring viability. Preferred females were not significantly more fecund and did not produce more viable eggs or offspring than non-preferred females. Male mate preferences were therefore inconsistent with both the direct- and indirect-fitness benefits hypotheses under the conditions of our experiment. Our null results leave us with an open question about what is driving the evolution of m

Maternal effects and range expansion: a key factor in a dynamic process?

Species that depend on ephemeral habitat often evolve distinct dispersal strategies in which the propensity to disperse is closely integrated with a suite of morphological, behavioural and physiological traits that influence colonizing ability. These strategies are maintained by natural selection resulting from spatial and temporal variation in resource abundance and are particularly evident during range expansion. Yet the mechanisms that maintain close alignment of such strategies with resource availability, integrate suites of dispersal traits and generate variability in dispersal propensity are rarely known. Breeding females can influence offspring phenotype in response to changes in current environmental conditions, making maternal effects uniquely suited to bridge fluctuations in resource abundance in the maternal generation and variation in offspring dispersal ability. Western bluebirds' (Sialia mexicana) dependence on nest cavities—an ephemeral resource—has led to the evolution of two distinct dispersal phenotypes: aggressive males that disperse and non-aggressive males that remain philopatric and cooperate with their relatives. Over the last 40 years, western bluebirds rapidly expanded their geographical range, providing us with an opportunity to test, in newly established populations, the importance of maternal effects for generating variability in dispersal propensity. Here, I show that, under variable resource conditions, breeding females group offspring of different competitive ability in different positions in the egg-laying order and, consequently, produce aggressive males that are more likely to disperse when resources are low and non-aggressive philopatric males when resources are abundant. I then show experimentally that the association between resource availability and sex-specific birth order is robust across populations. Thus, this maternal effect enables close tracking of resource availability and may explain how variation in dispersal is generated in newly colonized populations. More generally, these results suggest that, as a key source of variation in colonizing phenotypes, maternal effects are of crucial importance for understanding the dynamics of range expansion