Behavioral Ecology Advance Access originally published online on January 23, 2007
Behavioral Ecology 2007 18(2):467-476; doi:10.1093/beheco/arl108
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Clutch-size adjustments and skew models: effects on reproductive partitioning and group stability
Department of Behavioural Ecology, Zoology Institute, University of Bern, Wohlenstrasse 50a, CH-3032 Hinterkappelen, Switzerland
Address correspondence to I.M. Hamilton, who is now at the Department of Evolution, Ecology and Organismal Biology, The Ohio State University, 318 West 12th Avenue, Columbus, OH 43210, USA. E-mail: hamilton.598{at}osu.edu
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Abstract |
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Reproductive skew theory seeks to integrate social and ecological factors thought to influence the division of reproduction among group-living animals. However, most reproductive skew models only examine interactions between individuals of the same sex. Here, we suggest that females can influence group stability and conflict among males by modifying their clutch size and may do so if they benefit from the presence of subordinate male helpers or from reduced conflict. We develop 3 models, based on concessions-based, restraint, and tug-of-war models, in which female clutch size is variable and ask when females will increase their clutch size above that which would be optimal in the absence of male–male conflict. In concessions-based and restraint models, females should increase clutch size above their optima if the benefits of staying for subordinate males are relatively low. Relatedness between males has no effect on clutch size. When females do increase clutch size, the division of reproduction between males is not influenced by relatedness and does not differ between restraint and concessions-based models. Both of these predictions are in sharp contrast to previous models. In tug-of-war models, clutch size is strongly influenced by relatedness between males, with the largest clutches, but the fewest surviving offspring, produced when males are unrelated. These 3 models demonstrate the importance of considering third-party interests in the decisions of group-living organisms.
Key words: brood size, conflict reduction, dominance hierarchy, male quality, mate choice.
Received 14 July 2006; revised 25 October 2006; accepted 20 December 2006.