The evolution of avian parental care (original) (raw)
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Mate guarding as a key factor in the evolution of parental care in birds
The evolution of male parental care in vertebrates with internal fertilization must have been preceded by a stage in which males profit by staying with the female after copulation. This paper discusses the results of a series of computer simulations to determine the pay-off to post-copulatory mate guarding under various conditions. Guarding is promoted by asynchrony in fertility of the females, high copulation frequencies of females, preference of females for males using the guarding strategy, and mate fidelity of guarded females. Moreover, it is demonstrated that, under several conditions, apparently those operating in a natural environment, the success of the guarding strategy is inversely related to its frequency in the population. This implies that both the guarding and the non-guarding strategy can be maintained in the same population. This phenomenon is put forward as a key factor determining the pathways in the evolution of parental care.
Male parental care, diVerential parental investment by females and sexual selection
1998
Males play a variable parental role in reproduction, ranging from no male parental care to extensive male care. Females may acquire either direct or indirect fitness benefits from their mate choice, and direct fitness benefits include male parental care. Theoreticians have traditionally emphasized direct fitness benefits to females in species with extensive male parental care. We review the literature and show extensive variation in the patterns of male care, related to the attractiveness of males to females. At one extreme of this continuum, females invest differentially in parental care, investing more when paired with attractive males. The costs of female parental care and other aspects of parental investment may be balanced by benefits in terms of more attractive sons and/or more viable offspring. At the other extreme, in species with extensive direct fitness benefits, males with preferred sexual phenotypes provide the largest relative share of parental care. A comparative study of birds revealed that the extent of the differential female parental investment was directly related to the frequency of extra-pair paternity. Since extra-pair paternity may arise mainly as a consequence of female choice for indirect fitness benefits, this result supports our prediction that differential parental investment is prevalent in species where females benefit indirectly from their mate choice. The consequences for sexual selection theory of these patterns of male care in relation to male attractiveness are emphasized.
Proceedings of the Royal Society B: Biological Sciences, 2008
Parents often conflict over how much care to provide to their offspring. This conflict is expected to produce a negative relationship between male and female parental care, the strength of which may be mediated by both ecological and life-history variables. Previous studies have observed such trade-offs, but it is not known how generally they occur. Traditional views of sexual conflict place great importance on ecological factors in determining levels of parental care, whereas alternative views propose that the key determinant is mating opportunity. We carried out a broad-scale comparative study of parental conflict using 193 species from 41 families of birds. Using phylogenetic comparative analysis, we establish the generality of intersexual parental care conflict. We also show that parental conflict, as indicated by the disparity in care between the male and the female, depends on offspring development and mating opportunities, since in precocial species both males and females res...
Who cares? Quantifying the evolution of division of parental effort
Methods in Ecology and Evolution, 2010
1. Determining the factors that shape the unequal division of parental effort between the sexes is key to understanding the evolution of mating systems and sexual cooperation and conflict. The range of possible care strategies may be constrained, however, by the duration of the care period. Thus, comparative analyses of parental effort should consider both these dimensions of care; here, we present a method for quantifying parental care that does this. 2. We test three models of the relationship between care duration and the division of parental effort. Using detailed information on parental effort for 330 bird species from 13 families, we use Linear Mixed Effects models and Phylogenetically Weighted Generalized Least Squares models to analyse the relationship between the two dimensions of care. These models provide a starting point for more detailed comparative analyses of the role of covariates, such as sexual size dimorphism on determining the division of parental effort. 3. Within families, although males generally provide less care than females, their relative role often increases with the duration of the care period. Across all species, care strategies vary more in species with short development times. 4. Understanding the evolution of parental care strategies requires consideration of the total duration of care in addition to the division of parental effort. Our method provides a simple means to incorporate both dimensions of care into more extensive comparative analyses.
Parental care and adaptive brood sex ratio manipulation in birds
Philosophical Transactions of the Royal Society B: Biological Sciences, 2002
Under many circumstances, it might be adaptive for parents to bias the investment in offspring in relation to sex. Recently developed molecular techniques that allow sex determination of newly hatched offspring have caused a surge in studies of avian sex allocation. Whether females bias the primary brood sex ratio in relation to factors such as environmental and parental quality is debated. Progress is hampered because the mechanisms for primary sex ratio manipulation are unknown. Moreover, publication bias against nonsignificant results may distort our view of adaptive sex ratio manipulation. Despite this, there is recent experimental evidence for adaptive brood sex ratio manipulation in birds. Parental care is a particularly likely candidate to affect the brood sex ratio because it can have strong direct effects on the fitness of both parents and their offspring. We investigate and make predictions of factors that can be important for adaptive brood sex ratio manipulation under different patterns of parental care. We encourage correlational studies based on sufficiently large datasets to ensure high statistical power, studies identifying and experimentally altering factors with sex-differential fitness effects that may cause brood sex ratio skew, and studies that experimentally manipulate brood sex ratio and investigate fitness effects.
American Naturalist, 2002
Males and females are often defined by differences in their energetic investment in gametes. In most sexual species, females produce few large ova, whereas males produce many tiny sperm. This difference in initial parental investment is presumed to exert a fundamental influence on sex differences in mating and parental behavior, resulting in a taxonomic bias toward parental care in females and away from parental care in males. In this article, we reexamine the logic of this argument as well as the evolutionarily stable strategy (ESS) theory often used to substantiate it. We show that the classic ESS model, which contrasts parental care with offspring desertion, violates the necessary relationship between mean male and female fitness. When the constraint of equal male and female mean fitness is correctly incorporated into the ESS model, its results are congruent with those of evolutionary genetic theory for the evolution of genes with direct and indirect effects. Male parental care evolves whenever half the magnitude of the indirect effect of paternal care on offspring viability exceeds the direct effect of additional mating success gained by desertion. When the converse is true, desertion invades and spreads. In the absence of a genetic correlation between the sexes, the evolution of paternal care is independent of maternal care. Theories based on sex differences in gametic investment make no such specific predictions. We discuss whether inferences about the evolution of sex differences in parental care can hold if the ESS theory on which they are based contains internal contradictions.
Sexual conflict over parental care in a species with female and male brood desertion
Animal Behaviour, 2007
Each parent has limited resources to invest in current reproduction, so each parent would benefit if its mate did more of the work, which generates a sexual conflict between parents. Parental care behaviour is an adaptive decision, involving trade-offs between remating (and consequently desertion of the brood) and continuing parental effort. The rock sparrow, Petronia petronia, is an unusual species in which brood desertion can occur in both sexes. Consequently, the rock sparrow is a good species to investigate the behavioural response of parents to the desertion by their mates and whether sexual difference in this response exists. We compared parental effort of pair members divided into three groups: pairs that cooperated, females that deserted the brood and males that deserted. During the period of biparental care, females fed offspring more often than males, but there were no differences among the three groups. Following desertion the total amount of care in biparental, female-only and male-only broods differed, because both sexes adjusted their care to the absence of their mates, but females overcompensated the mate's absence while males only partially compensated. Nestling survival rate was positively correlated with feeding rate and the mean survival rate was lower in the male-only broods. We suggest that both parents, in a negotiation process, would benefit from withholding parental investment, as proposed in recent theoretical models on sexual conflict over parental care. Altogether our results show an unexpected plastic response of parents to care during the desertion process.