Evolution

Good for You, Good for Me, Too

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Science  03 Dec 2010:
Vol. 330, Issue 6009, pp. 1289
DOI: 10.1126/science.330.6009.1289-c

In most examples of cooperative breeding, reproductive individuals are assisted by closely related helpers. Although helpers sacrifice their own ability to reproduce, they obtain an indirect fitness benefit from improving survival in their kin (kin theory). Increasingly, however, cooperative breeding has been revealed among unrelated individuals. In greater anis (Crotophaga major), multiple pairs of birds will cooperate to build nests and raise and defend young. Riehl has now shown that these pairs are relatively unrelated, thus cooperation cannot be explained by kin theory. Instead, she finds that the individual fitness of all the pairs is increased when pairs cooperate, despite initial reproductive competition generated during egg-laying. Three pair groups were able to obtain and defend prime nesting sites better than two pair groups, and pairs attempting to breed alone failed in all observed instances. Furthermore, there was no cost to individual fitness on the basis of the number of eggs laid, most likely because females changed their laying order across years. In unrelated cooperative breeders, what's good for “the many” is most likely also good for “the one.”

Proc. R. Soc. London Ser. B 10.1098/rspb.2010.1752 (2010).

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