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Journal Article

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Evolutionary Ecology Research





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Question: How well are genetic benefits hypotheses for extra-pair paternity supported by empirical evidence?

Data incorporated: Almost all published studies testing for genetic benefits from 1980 onwards (121 papers, 55 species).

Analysis methods: Collected key features and findings of each study in a database. Determined overall level of support for both good genes and compatible genes hypotheses. Conducted a formal meta-analysis on a subset of studies asking the following questions: (1) Do extra-pair mates of females have different phenotypes than their within-pair mates? (2) Do extra-pair offspring differ in viability from within-pair offspring? (3) Is there a correlation between the genetic similarity of a social pair and the incidence of extra-pair paternity?

Results: Both the good genes and compatible genes hypotheses failed to be supported in more than half of the species studied. The meta-analysis shows that extra-pair males are on average larger and older than within-pair males, but not different in terms of secondary sexual traits, condition or relatedness to the female. No difference was found between extra-pair and within-pair young in survival to the next breeding season. We found no significant correlation between pair genetic similarity and extra-pair paternity.

Conclusions: Genetic benefits are not strongly supported by available empirical data. New hypotheses are needed.


At the time of publication, author Erol Akçay was affiliated with Stanford University. Currently, he is a faculty member at the Department of Biology at the University of Pennsylvania.



Date Posted: 02 October 2015

This document has been peer reviewed.