Genetic monogamy across variable demographic landscapes in cooperatively breeding Florida scrub-jays

Abstract

Variation in ecological and demographic characteristics may alter the value of extrapair paternity (EPP) for socially monogamous species, thereby leading to variation in mating strategies among conspecific populations. Environmental factors influencing the need for parental care, and demographic factors influencing relatedness of social pairs or availability of unrelated extrapair partners, are both predicted to influence the direct and indirect benefits of EPP in cooperatively breeding birds. We examined genetic mating strategies in 3 long-term study populations of cooperatively breeding Florida scrub-jays (FSJs; Aphelocoma coerulescens) in which the value of EPP—or opportunities for it—was likely to vary: a fragmented site with a high frequency of inbreeding (potentially elevating the value of EPP as a means of increasing offspring heterozygosity); a suburban population with high rates of brood reduction (potentially elevating the value of shared parental investment); and a wildland site with a high frequency of unrelated breeders and opposite-sex auxiliaries (potentially elevating the opportunity for shared within-group parentage). Despite these differences, genetic monogamy dominated at all sites: 100% of the offspring sampled from the suburban site (144 offspring) and fragmented site (258 offspring), and 99.5% of offspring from the wildland site (367 of 369 offspring) were produced monogamously. Rare exceptions in our study populations demonstrate that, even in the FSJ, genetic monogamy is a plastic trait. The near ubiquity of genetic monogamy across 3 ecologically different study sites, however, suggests that this tendency toward monogamy is impervious to the population-level environmental and social variation that we documented. Key words: Aphelocoma coerulescens, extrapair paternity, Florida scrub-jay, genetic monogamy. [Behav Ecol]