Individual variation and the resolution of conflict over parental care in penduline tits

Abstract

Eurasian penduline tits (Remiz pendulinus) have an unusually diverse breeding system consisting of frequent male and female polygamy, and uniparental care by the male or the female. Intriguingly, 30 to 40 per cent of all nests are deserted by both parents. To understand the evolution of this diverse breeding system and frequent clutch desertion, we use 6 years of field data to derive fitness expectations for males and females depending on whether or not they care for their offspring. The resulting payoff matrix corresponds to an asymmetric Snowdrift Game with two alternative evolutionarily stable strategies (ESSs): female-only and male-only care. This, however, does not explain the polymorphism in care strategies and frequent biparental desertion, because theory predicts that one of the two ESSs should have spread to fixation. Using a bootstrapping approach, we demonstrate that taking account of individual variation in payoffs explains the patterns of care better than a model based on the average population payoff matrix. In particular, a model incorporating differences in male attractiveness closely predicts the observed frequencies of male and female desertion. Our work highlights the need for a new generation of individual-based evolutionary game-theoretic models.

Sexual Conflict between Parents: Offspring Desertion and Asymmetrical Parental Care

“…There are situations in which both uniparental care and biparental care are ESSs, and they can coexist in a population (McNamara et al 2000;Kokko and Jennions 2008;Klug et al 2012;van Dijk et al 2012). The presence of several care patterns in a single population is consistent with theoretical results (see the section Diversity of Care Strategies), although alternative explanations of coexisting caring strategies are also possible-for instance, age-dependent care strategies and/ or temporal or spatial variation in costs and benefits of care for different members of the population.…”

“…However, it is plausible that some of these transitions are largely (or entirely) the result of changes in male and/or female behavior as they are trying to resolve the conflict. First, for a given set of costs and benefits, multiple patterns of care may occur in a population; this may be the result of mixed evolutionarily stable strategies (ESSs) (Webb et al 1999), to different behavioral interactions between parents Johnstone et al 2014), or to social interactions between parents and other members of a population that can stabilize different ESSs in a coevolutionary process that involves mate choice, mating behavior, and parental care (McNamara et al 2000;van Dijk et al 2012). Second, an important insight from evolutionary game theory is that as males (or females) attempt to attain their respective fitness optima, they may change the cost and benefit functions for their mates, and thus influence the fitness landscape for the opposite sex (McNamara and Weissing 2010).…”

“…Deserting the clutch increased the reproductive success of the deserting males, because many of these males found a new mate and renested. Desertion, however, was costly to deserted females, because they either deserted the clutch themselves and thusdoomed the offspring to death,or stayed with the offspring for about one month and cared for them until they became independent (Szentirmai et al 2007;van Dijk et al 2012). The fitness consequences of desertion and caring in males are mirrored by fitness consequences in females.…”

“…Numerous models have been developed to understand how parents interact with each other and with their offspring (Trivers 1972;Maynard Smith 1977;Houston and Davies 1985;Balshine-Earn and Earn 1998;McNamara et al 1999McNamara et al , 2000Webb et al 1999;Johnstone and Hinde 2006;Johnstone et al 2014). Parental care research is one field in which empiricists are extensively testing the predictions of evolutionary game theoretic models in both the laboratory and wild populations (Székely et al 1996;Balshine-Earn and Earn 1998;Harrison et al 2009;Klug et al 2012;Lessells 2012;van Dijk et al 2012), although the congruence between theoretical and empirical work is not as tight as often assumed (Houston et al 2013). Finally, parental care-wherever it occurs-is often a major component of fitness, because whether the offspring are cared for or abandoned has a large impact on their survival, maturation, and reproduction .…”

Immunoreactivity Distribution of Vasotocin and Vasoactive Intestinal Peptide in Brain Nuclei of Two Songbird Species with Different Breeding Systems

“…A few days after the start of egg laying, one of the birds, usually the male, deserts the nest leaving the incubation and parental care to the mate [Pogány, 2009]. Biparental care has never been observed in this species [Van Dijk et al, 2012]. Rupture of the social bond occurs very quickly [Van Dijk et al, 2012].…”