Higher reproductive skew among birds than mammals in cooperatively breeding species

Raihani, Nichola; Clutton‐Brock, Tim

doi:10.1098/rsbl.2010.0159

Cited by 20 publications

(35 citation statements)

References 33 publications

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“…Interestingly, in cooperative mammals, dispersal is often male-biased, and females generally form the surplus sex and are more likely to help than males. This difference between birds and mammals may be due to better opportunities for subordinate females to breed in mammals compared to birds, who have to compete for a space in the nest to lay an egg [69]. The biased sex ratio of helpers is not always directly related to ASR bias and a link between them might not be causative, for example, because helper sex ratio may be determined by biased offspring sex ratio, or be due to sex-specific differences in ultimate benefits of helping.…”

Section: (B) Adult Sex Ratio Bias and The Evolution Of Cooperative Brmentioning

confidence: 99%

Adult sex ratios and their implications for cooperative breeding in birds

Komdeur

Székely

Long

et al. 2017

Phil. Trans. R. Soc. B

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Cooperative breeding is a form of breeding system where in addition to a core breeding pair, one or more usually non-breeding individuals provide offspring care. Cooperative breeding is widespread in birds, but its origin and maintenance in contemporary populations are debated. Although deviations in adult sex ratio (ASR, the proportion of males in the adult population) have been hypothesized to influence the occurrence of cooperative breeding because of the resulting surplus of one sex and limited availability of breeding partners, this hypothesis has not been tested across a wide range of taxa. By using data from 188 bird species and phylogenetically controlled analyses, we show that cooperatively breeding species have more male-biased ASRs than non-cooperative species. Importantly, ASR predicts helper sex ratio: in species with more male-biased ASR, helper sex ratio is also more male biased. We also show that offspring sex ratios do not predict ASRs, so that the skewed ASRs emerge during the period when individuals aim to obtain a breeding position or later during adulthood. In line with this result, we found that ASR (among both cooperatively and non-cooperatively breeding species) is inversely related to sex bias in dispersal distance, suggesting that the cost of dispersal is more severe for the further-dispersing sex. As females usually disperse further in birds, this explains the generally male-biased ASR, and in combination with benefits of philopatry for males, this probably explains why ASR is more biased in cooperatively breeding species. Taken together, our results suggest that a sex bias in helping in cooperatively breeding species relates to biased ASRs. We propose that this relationship is driven by sex-specific costs and benefits of dispersal and helping, as well as other demographic factors. Future phylogenetic comparative and experimental work is needed to establish how this relationship emerges.This article is part of the themed issue 'Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'.

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Section: (B) Adult Sex Ratio Bias and The Evolution Of Cooperative Brmentioning

confidence: 99%

Adult sex ratios and their implications for cooperative breeding in birds

Komdeur

Székely

Long

et al. 2017

Phil. Trans. R. Soc. B

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“…Intermediate between these two extremes are cooperative groups in which reproduction is unequally shared among cobreeders-for example, in which an ostensibly nonreproductive helper male sires a minority of nestlings in a dominant's nest or a helper female lays a minority of eggs. Understanding the sources of variation in reproduction among group members is crucial to understanding why animals live in social groups and remains a central focus of studies of the evolution of cooperative breeding (Raihani and Clutton-Brock 2010;Alberts 2012;Green et al 2014;Chak et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Kinship and Incest Avoidance Drive Patterns of Reproductive Skew in Cooperatively Breeding Birds

Riehl¹

2017

The American Naturalist

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Social animals vary in how reproduction is divided among group members, ranging from monopolization by a dominant pair (high skew) to equal sharing by cobreeders (low skew). Despite many theoretical models, the ecological and life-history factors that generate this variation are still debated. Here I analyze data from 83 species of cooperatively breeding birds, finding that kinship within the breeding group is a powerful predictor of reproductive sharing across species. Societies composed of nuclear families have significantly higher skew than those that contain unrelated members, a pattern that holds for both multimale and multifemale groups. Within-species studies confirm this, showing that unrelated subordinates of both sexes are more likely to breed than related subordinates are. Crucially, subordinates in cooperative groups are more likely to breed if they are unrelated to the opposite-sex dominant, whereas relatedness to the same-sex dominant has no effect. This suggests that incest avoidance, rather than suppression by dominant breeders, may be an important proximate mechanism limiting reproduction by subordinates. Overall, these results support the ultimate evolutionary logic behind concessions models of skew-namely, that related subordinates gain indirect fitness benefits from helping at the nests of kin, so a lower direct reproductive share is required for selection to favor helping over dispersal-but not the proximate mechanism of dominant control assumed by these models.

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“…2006; Gilchrist 2006; Kutsukake & Clutton‐Brock 2006). Compared to birds, female mammals appear to be less able to prevent subordinate breeding (Raihani & Clutton‐Brock 2010), but where it occurs, female age, aggressiveness, individual body condition and demographic factors play important roles in determining and maintaining dominant status (Kutsukake & Clutton‐Brock 2006; Hodge et al. 2008).…”

Section: Introductionmentioning

confidence: 99%

“…Under some conditions, one dominant female prevents all or most other females from breeding, using a combination of behavioural and physiological mechanisms, such as interference with subordinate mating, aggression, reproductive suppression, eviction of rivals and infanticide (Hoogland 1985;Cant et al 2001Cant et al , 2010Clutton-Brock 2002Clutton-Brock et al 2006;Gilchrist 2006;Kutsukake & Clutton-Brock 2006). Compared to birds, female mammals appear to be less able to prevent subordinate breeding (Raihani & Clutton-Brock 2010), but where it occurs, female age, aggressiveness, individual body condition and demographic factors play important roles in determining and maintaining dominant status (Kutsukake & Clutton-Brock 2006;Hodge et al 2008). Because subordinate females typically have poor prospects of breeding elsewhere, they can maximize their inclusive fitness by helping related dominants to rear their offspring (Clutton-Brock 2009).…”

Section: Introductionmentioning

confidence: 99%

Female reproductive competition in Eulemur rufifrons: eviction and reproductive restraint in a plurally breeding Malagasy primate

Kappeler

Fichtel

2011

Molecular Ecology

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In mammals with female philopatry, co-resident females inevitably compete with each other for resources or reproductive opportunities, thereby reducing the kin-selected benefits of altruism towards relatives. These counteracting forces of cooperation and competition among kin should be particularly pronounced in plurally breeding species with limited alternative breeding opportunities outside the natal group. However, little is still known about the costs of reproductive competition on females' fitness and the victims' potential counter-strategies. Here we summarize long-term behavioural, demographic and genetic data collected on a plurally breeding primate from Madagascar to illuminate mechanisms and effects of female reproductive competition, focusing on forcible eviction and potential reproductive restraint. The main results of our study indicate that females in groups of redfronted lemurs (Eulemur rufifrons) above a critical size suffer from competition from their close relatives: females in larger groups face an increased probability of not giving birth as well as a higher probability of being evicted, especially during the annual mating and birth seasons. Eviction is not predicted by the number of adult females, the number of close female relatives, female age or inter-annual variation in rainfall but only by total group size. Thus, eviction in this species is clearly linked with reproductive competition, it cannot be forestalled by reproductive restraint or having many relatives in the group, and it occurs in the absence of a clear dominance hierarchy. Our study therefore also underscores the notion that potential inclusive fitness benefits from living with relatives may have been generally over-rated and should not be taken for granted.

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Higher reproductive skew among birds than mammals in cooperatively breeding species

Cited by 20 publications

References 33 publications

Adult sex ratios and their implications for cooperative breeding in birds

Adult sex ratios and their implications for cooperative breeding in birds

Kinship and Incest Avoidance Drive Patterns of Reproductive Skew in Cooperatively Breeding Birds

Female reproductive competition in Eulemur rufifrons: eviction and reproductive restraint in a plurally breeding Malagasy primate

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