Behavioral Ecology Advance Access published online on June 15, 2005
Behavioral Ecology, doi:10.1093/beheco/ari062
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1 Field of Ecology and Evolutionary Biology, Cornell University, Ithaca NY 14853
* To whom correspondence should be addressed. Reproductive skew models attempt to predict the fraction of reproduction contributed by each individual that participates in a communal brood. One potential limitation of these models is that individuals make a single, fixed decision about group membership and reproductive allocation at the beginning of the breeding period. While this is appropriate for animals that reproduce in a synchronous bout, many cooperative breeders produce offspring over a prolonged period of time. It is likely that these species adjust reproductive allocation and group membership over time in response to temporal shifts in group productivity and ecological constraints. In this paper we adapt transactional models of reproductive skew to a continuous form, generating time-dependent functions of reproductive allocation. We derive a general method for predicting temporal changes in group membership as well as a general expression for reproductive skew across the regions over which a group is stable. Using a linear approximation for time-dependent reproduction, we derive new expressions for reproductive skew in cases where the subordinate departs during the breeding period. In this case we find that the traditional model always overestimates the subordinate's share of reproduction when dominants are in control of both reproductive shares and group membership (i.e., concessions models). Conversely, we find that the traditional model always underestimates the subordinate's share of reproduction when subordinates are in control of reproductive shares (i.e., constraint models). We discuss the implications of these new calculations in relation to the traditional skew models and more recent empirical tests of reproductive skew in animal societies.
Received May 28, 2003
Revised April 25, 2005
Accepted May 17, 2005
Article
Predicting the temporal dynamics of reproductive skew and group membership in communal breeders
2 Department of Neurobiology and Behavior, Cornell University, Ithaca NY 14853
Andrew G. Zink, E-mail: agzink{at}ucdavis.edu
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