Conflict between parents over care

Abstract

Conflict between parents over care of young arises when the young benefit from the effort of both parents, but each parent suffers a reduction in future reproductive success as a consequence of its own effort. Here, we review existing models and argue that they fail to capture many important components of parental conflict. For example, we lack adequate models of how a parent should compensate for a reduction in the effort of its mate. These models should incorporate the process by which decisions are reached. Recent theory suggests that a parent benefits by handicapping itself, and more experimental and theoretical work on this topic could be fruitful. We also need more theoretical work on attractiveness that incorporates consistent interactions between males and females.There are many forms of parental care and many ways in which care can be costly to a parent, in that it reduces their reproductive success in other breeding attempts [1,2]. Parental care involves a high level of energy expenditure, which might reduce the condition of the parent at the end of the breeding season. This can reduce the future survival of the care-provider and, hence, its probability of breeding the following year. A parent that deserts its mate and young has greater opportunities to pair with a new partner within the current breeding season than does a parent that cares. Even if a male remains with his mate and young, it might be possible to increase his chances of copulating with females other than his mate by decreasing his level of care and devoting more time to courting other females [3]. Such matings are known as extra-pair copulations (EPCs).Although the details vary across species, the success of the young generally depends on the care from both parents, whereas the cost to a parent depends on its own effort. Thus, a conflict of interest emerges [4,5], with each parent preferring the other to do the hard work. Here, we focus on sexual conflict over care, although the parents might also disagree about family size, timing of breeding or the sex ratio of their offspring [6]. For a broader account of sexual conflict, see [7].The benefit that results from a particular level of care by a parent depends on the behaviour of its partner, whereas the cost of care in terms of lost mating opportunities depends on the behaviour of other members of the population. For example, if a male deserts, his chances of obtaining a new mate will depend on the number of females that have also deserted their mate and are hence available. If a male seeks EPCs, then his chances of obtaining them depend on the receptiveness of females in the population and the extent to which males allocate their time to guarding their mates from other males as opposed to caring for their young or seeking EPCs [8]. These complex interactions make it difficult to use verbal arguments to predict the level of care that will evolve. Theory attempts to predict the outcome of evolution by constructing mathematical models that expose the logic of parental conflict. Here, we co...

Yolk androgens do not appear to mediate sexual conflict over parental investment in the collared flycatcher Ficedula albicollis

“…In species with biparental care, females and males are in conflict over the amount of parental care they provide to their offspring (Trivers, 1972; reviewed by Arnquist and Rowe, 2005;Houston et al, 2005;Lessells, 2006;Hartley and Royle, 2007). For each parent, increased investment reduces the parent's future reproductive success and survival prospects (e.g.…”

“…For each parent, increased investment reduces the parent's future reproductive success and survival prospects (e.g. Williams, 1966;Roff, 1992;Parker et al, 2002), and therefore it would be favourable for one parent to shift labour to the other (Parker et al, 2002;Houston et al, 2005). The parents' decision about how much to invest in the offspring depends on offspring need and/or brood value, as well as the feeding behaviour of the other parent (e.g.…”

The quantitative genetics of sex differences in parenting

“…Current theory and empirical research typically examine potential sex differences in the costs and benefits of care to address specialization (6)(7)(8).…”

“…However, in a number of species, both sexes will display the full range of parental behaviors following the loss of the partner (i.e., when the other sex dies or is removed) (3,6). These systems provide an opportunity for quantifying the genetic variation underlying parental care behaviors in both sexes and assess whether or not this variation differs.…”

The evolution of postpairing male mate choice

“…Generally, each parent should prefer to shift more of the costly care for the offspring onto its mate, and then conflict arises (Trivers 1972; Houston et al. 2005). It has been expected that sexually antagonistic coevolution between traits that function to increase care by the other sex, and those that function to resist such manipulations, would resolve such conflicts (Chapman et al.…”