Subordinate females in the cooperatively breeding Seychelles warbler obtain direct benefits by joining unrelated groups

Groenewoud, Frank, Kingma, Sjouke A., Hammers, Martijn, Dugdale, Hannah L., Burke, Terry, Richardson, David S. ORCID: https://orcid.org/0000-0001-7226-9074 and Komdeur, Jan (2018) Subordinate females in the cooperatively breeding Seychelles warbler obtain direct benefits by joining unrelated groups. Journal of Animal Ecology, 87 (5). pp. 1251-1263. ISSN 0021-8790

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Abstract

1. In many cooperatively breeding animals, a combination of ecological constraints and benefits of philopatry favours offspring taking a subordinate position on the natal territory instead of dispersing to breed independently. However, in many species individuals disperse to a subordinate position in a non-natal group ("subordinate between-group" dispersal), despite losing the kin-selected and nepotistic benefits of remaining in the natal group. It is unclear which social, genetic and ecological factors drive between-group dispersal. 2. We aim to elucidate the adaptive significance of subordinate between-group dispersal by examining which factors promote such dispersal, whether subordinates gain improved ecological and social conditions by joining a non-natal group, and whether between-group dispersal results in increased lifetime reproductive success and survival. 3. Using a long-term dataset on the cooperatively-breeding Seychelles warbler (Acrocephalus sechellensis), we investigated how a suite of proximate factors (food availability, group composition, age and sex of focal individuals, population density) promote subordinate between-group dispersal by comparing such dispersers with subordinates that dispersed to a dominant position or became floaters. We then analysed whether subordinates that moved to a dominant or non-natal subordinate position, or became floaters, gained improved conditions relative to the natal territory, and compared fitness components between the three dispersal strategies. 4. We show that individuals that joined another group as non-natal subordinates were mainly female and that, similar to floating, between-group dispersal was associated with social and demographic factors that constrained dispersal to an independent breeding position. Between-group dispersal was not driven by improved ecological or social conditions in the new territory and did not result in higher survival. Instead, between-group dispersing females often became co-breeders, obtaining maternity in the new territory, and were likely to inherit the territory in the future, leading to higher lifetime reproductive success compared to females that floated. Males never reproduced as subordinates, which may be one explanation why subordinate between-group dispersal by males is rare. 5. Our results suggest that subordinate between-group dispersal is used by females to obtain reproductive benefits when options to disperse to an independent breeding position are limited. This provides important insight into the additional strategies that individuals can use to obtain reproductive benefits.

Item Type:	Article
Uncontrolled Keywords:	benefits of philopatry,subordinate between‐group dispersal,cooperative breeding,joint nesting,natal dispersal,communal breeding
Faculty \ School:	Faculty of Science > School of Biological Sciences
UEA Research Groups:	Faculty of Science > Research Centres > Centre for Ecology, Evolution and Conservation Faculty of Science > Research Groups > Organisms and the Environment
Depositing User:	Pure Connector
Date Deposited:	16 May 2018 13:31
Last Modified:	12 May 2023 13:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/67086
DOI:	10.1111/1365-2656.12849

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