What can we really say about relatedness and extrapair paternity: A comment on Arct et al.

One prevailing challenge in behavioral and evolutionary ecology is to explain the evolution and persistence of polyandry (i.e., female mating with multiple males within single reproductive events, Pizzari and Wedell 2013 ). One particular objective that has motivated numerous empirical studies is to identify fitness benefits of extrapair reproduction to socially paired females; yet such benefits remain elusive. Because there are often no obvious direct benefits of extrapair reproduction, some genetic effect that increases offspring fitness is widely postulated. One broad hypothesis is that females might mate with extrapair males that are less closely related than their socially paired male and thereby produce extrapair offspring that are less inbred (and hence fitter) than their alternative within-pair offspring. This hypothesis generates several testable predictions, including that extrapair paternity (EPP) will increase with a female’s relatedness to her socially paired male ( Kempenaers 2007 ; Wetzel and Westneat 2009 ).