Faculty Opinions recommendation of Inclusive fitness consequences of dispersal decisions in a cooperatively breeding bird, the long-tailed tit (Aegithalos caudatus).

Natal dispersal is a demographic trait with profound evolutionary, ecological, and behavioral consequences. However, our understanding of the adaptive value of dispersal patterns is severely hampered by the difficulty of measuring the relative fitness consequences of alternative dispersal strategies in natural populations. This is especially true in social species, in which natal philopatry allows kin selection to operate, so direct and indirect components of inclusive fitness have to be considered when evaluating selection on dispersal. Here, we use lifetime reproductive success data from a long-term study of a cooperative breeder, the long-tailed titAegithalos caudatus, to quantify the direct and indirect components of inclusive fitness. We show that dispersal has a negative effect on the accrual of indirect fitness, and hence inclusive fitness, by males. In contrast, the inclusive, predominantly direct, fitness of females increases with dispersal distance. We conclude that the conflicting fitness consequences of dispersal in this species result in sexually antagonistic selection on this key demographic parameter.

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Hamilton's inclusive fitness maintains heritable altruism polymorphism through rb = c

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1710215115 ◽

2018 ◽

Vol 115 (8) ◽

pp. 1860-1864 ◽

Cited By ~ 14

Author(s):

Changcao Wang ◽

Xin Lu

Keyword(s):

Reproductive Success ◽

Inclusive Fitness ◽

Lifetime Reproductive Success ◽

Adult Males ◽

Breeding Bird ◽

Annual Fluctuation ◽

The Social ◽

Cooperatively Breeding ◽

Social Partners ◽

Indirect Fitness

How can altruism evolve or be maintained in a selfish world? Hamilton’s rule shows that the former process will occur when rb > c—the benefits to the recipients of an altruistic act b, weighted by the relatedness between the social partners r, exceed the costs to the altruists c—drives altruistic genotypes spreading against nonaltruistic ones. From this rule, we infer that altruistic genotypes will persist in a population by forming a stable heritable polymorphism with nonaltruistic genotypes if rb = c makes inclusive fitness of the two morphs equal. We test this prediction using the data of 12 years of study on a cooperatively breeding bird, the Tibetan ground tit Pseudopodoces humilis, where helping is performed by males only and kin-directed. Individual variation in ever acting as a helper was heritable (h2 = 0.47), and the resultant altruism polymorphism remained stable as indicated by low-level annual fluctuation of the percentage of helpers among all adult males (24–28%). Helpers’ indirect fitness gains from increased lifetime reproductive success of related breeders statistically fully compensated for their lifetime direct fitness losses, suggesting that rb = c holds. While our work provides a fundamental support for Hamilton’s idea, it highlights the equivalent inclusive fitness returns to altruists and nonaltruists mediated by rb = c as a theoretically and realistically important mechanism to maintain social polymorphism.

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Individuality in the contact calls of cooperatively breeding long-tailed tits (Aegithalos caudatus)

Behaviour ◽

10.1163/156853905774831918 ◽

2005 ◽

Vol 142 (11-12) ◽

pp. 1559-1575 ◽

Cited By ~ 32

Author(s):

S.P Sharp ◽

B.J. Hatchwell

Keyword(s):

Cross Correlation ◽

Function Analysis ◽

Quantitative Description ◽

Recognition System ◽

Breeding Bird ◽

Evolution Of Sociality ◽

Or Groups ◽

Cooperatively Breeding ◽

Contact Calls ◽

Aegithalos Caudatus

AbstractThe ability to discriminate between individuals or groups of individuals is important for the evolution of sociality. Individual vocal recognition is thought to be widespread in social birds, yet few studies have investigated its role in cooperatively breeding species. In long-tailed tits, helpers preferentially provide care to close kin, and individuals are able to discriminate between the vocalisations of kin and non-kin. However, the mechanism underlying this recognition system is unknown. Here we quantify the relative variation between and within individuals in three of the contact calls used by this species. Spectrographic cross-correlation revealed that two of these calls, the 'churr' and the 'triple', were individually distinct. We therefore analysed the variation in a series of acoustic parameters in each of these two vocalisations. For both the churr and the triple, discriminant function analysis was able to allocate calls to the correct individuals according to variation in several frequency parameters. We hypothesise that long-tailed tits are able to discriminate between the calls of conspecifics based on these parameters. This is the first quantitative description of potential recognition cues in a cooperatively breeding bird in which vocal discrimination is known to occur.

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The fitness consequences of kin-biased dispersal in a cooperatively breeding bird

Biology Letters ◽

10.1098/rsbl.2015.0336 ◽

2015 ◽

Vol 11 (7) ◽

pp. 20150336 ◽

Cited By ~ 7

Author(s):

Lea Pollack ◽

Dustin R. Rubenstein

Keyword(s):

Social Rank ◽

Group Living ◽

Breeding Bird ◽

Direct Benefits ◽

Fitness Consequences ◽

Cooperatively Breeding ◽

Potential Benefits ◽

Indirect Fitness ◽

Living Species

Cooperative alliances among kin may not only lead to indirect fitness benefits for group-living species, but can also provide direct benefits through access to mates or higher social rank. However, the immigrant sex in most species loses any potential benefits of living with kin unless immigrants disperse together or recruit relatives into the group in subsequent years. To look for evidence of small subgroups of related immigrants within social groups (kin substructure), we used microsatellites to assess relatedness between immigrant females of the cooperatively breeding superb starling, Lamprotornis superbus. We determined how timing of immigration led to kin subgroup formation and if being part of one influenced female fitness. Although mean relatedness in groups was higher for males than females, 26% of immigrant females were part of a kin subgroup with a sister. These immigrant sibships formed through kin recruitment across years more often than through coalitions immigrating together in the same year. Furthermore, females were more likely to breed when part of a kin subgroup than when alone, suggesting that female siblings form alliances that may positively influence their fitness. Ultimately, kin substructure should be considered when determining the role of relatedness in the evolution of animal societies.

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Social genetic and social environment effects on parental and helper care in a cooperatively breeding bird

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.0689 ◽

2015 ◽

Vol 282 (1810) ◽

pp. 20150689 ◽

Cited By ~ 18

Author(s):

Mark James Adams ◽

Matthew R. Robinson ◽

Maria-Elena Mannarelli ◽

Ben J. Hatchwell

Keyword(s):

Social Contexts ◽

Social Effects ◽

Breeding Bird ◽

Environment Effect ◽

Environment Effects ◽

Cooperatively Breeding ◽

Social Partners ◽

Aegithalos Caudatus ◽

The Individual

Phenotypes expressed in a social context are not only a function of the individual, but can also be shaped by the phenotypes of social partners. These social effects may play a major role in the evolution of cooperative breeding if social partners differ in the quality of care they provide and if individual carers adjust their effort in relation to that of other carers. When applying social effects models to wild study systems, it is also important to explore sources of individual plasticity that could masquerade as social effects. We studied offspring provisioning rates of parents and helpers in a wild population of long-tailed tits Aegithalos caudatus using a quantitative genetic framework to identify these social effects and partition them into genetic, permanent environment and current environment components. Controlling for other effects, individuals were consistent in their provisioning effort at a given nest, but adjusted their effort based on who was in their social group, indicating the presence of social effects. However, these social effects differed between years and social contexts, indicating a current environment effect, rather than indicating a genetic or permanent environment effect. While this study reveals the importance of examining environmental and genetic sources of social effects, the framework we present is entirely general, enabling a greater understanding of potentially important social effects within any ecological population.

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