ScienceDaily (July 27, 2005) — Males enjoy larger reproductive success by mating with many females, whereas the number of offspring per female does not increase by mating with many males. Furthermore, males run the risk of investing in offspring of other males if they provide parental care.

Nevertheless, in various species, males provide parental care and females mate with multiple males. For example, recent empirical studies show that extra-pair copulation frequently occurs in monogamous birds in which a "social" father provides intensive care for its "social" offspring. Can such pseudo-monogamy through the Darwinian theory of evolution?

A new study by Joe Yuichiro Wakano and Yasuo Ihara in the August 2005 issue of The American Naturalist investigates a game-theoretical model in which females gain a direct benefit by multiple mating from the paternal care they elicit for their offspring.

As a result, various combinations of male parental care and female multiple mating evolve. The parameters that directly favor male parental care, such as small cost of paternal care, have indirect positive effects on the evolution of female multiple mating, while they have negative effects in the opposite case. Both traits are more likely to evolve when the number of matings is smaller.

Based on the model result, the researchers provide a hypothesis explaining why pseudo-monogamy evolved in birds.

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Sponsored by the American Society of Naturalists, The American Naturalist is a leading journal in the fields of ecology and evolutionary biology and animal behavior. For more information, please see our website: www.journals.uchicago.edu/AN

Joe Yuichiro Wakano and Yasuo Ihara, "Evolution of male parental care and female multiple mating: Game-theoretical and two-locus diploid models"166:2 August 2005.

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