Mismatched partners that achieve postpairing behavioral similarity improve their reproductive success.
Résumé
Behavioral similarity between partners is likely to promote within-pair compatibility and to result in better
reproductive success. Therefore, individuals are expected to choose a partner that is alike in behavioral type.
However, mate searching is very costly and does not guarantee finding a matching partner. If mismatched
individuals pair, they may benefit from increasing their similarity after pairing. We show in a monogamous fish
species—the convict cichlid—that the behavioral similarity between mismatched partners can increase after
pairing. This increase resulted from asymmetrical adjustment because only the reactive individual became
more alike its proactive partner, whereas the latter did not change its behavior. The mismatched pairs that
increased their similarity not only improved their reproductive success but also raised it up to the level of
matched pairs. While most studies assume that assortative mating results from mate choice, our study suggests
that postpairing adjustment could be an alternative explanation for the high behavioral similarity between
partners observed in the field. It also explains why interindividual behavioral differences can be maintained
within a given population.