Abstract
Genetic analysis of avian mating systems has revealed that more than 70% of monogamous species show incidence of offspring parentage that does not match the social partner. Extra-pair parentage (EPP) has been linked to a variety of factors, including size and symmetry of ornamental traits, coloration, resource availability, and local conspecific density. We examined how ornamental plumage traits of individual Steller's jays (Cyanocitta stelleri) and territory characteristics influence genetic fidelity of socially monogamous pairs. We used seven highly polymorphic microsatellite markers to assign paternity to 79 offspring, and identified 12 (15.2%) as extra-pair young (EPY). Steller's jays with extra-pair young had significantly lower values of feather brightness and hue, indicating more ultraviolet-blue shifted coloration, and nested in closer proximity to the forest edge than Steller's jays with no detected EPY. Body size, crest height, asymmetry of ornamental crest stripes, as well as vegetative composition of territories and their proximity to supplemental feeders appeared to have little relationship to EPP. These results indicate that extra-pair parentage plays a role in the evolution of secondary sexual characteristics in both sexes, and suggest local density and availability of resources may influence Steller's jay mating dynamics.
Highlights
The resource-based nature of serial monogamy makes it the most prevalent mating strategy in avian species with finite resource availability [1], [2]
Griffith et al [5] suggest that the considerable variation in extra-pair parentage (EPP) among species could be explained by differences in life history and social structure, while within species EPP may vary according to ecological restrictions
Low Delta scores prevented confident assignment of the extra-pair mate for 75% of these cases, we restricted our statistical analysis to the 11 parents that gained extra-pair young (EPY) (6 males, 5 females) identified at the 95% confidence interval (Table 2)
Summary
The resource-based nature of serial monogamy makes it the most prevalent mating strategy in avian species with finite resource availability [1], [2]. Rates of extra-pair copulations (EPC) and resulting extra-pair parentage (EPP) vary between species and populations [6]. Griffith et al [5] suggest that the considerable variation in EPP among species could be explained by differences in life history and social structure, while within species EPP may vary according to ecological restrictions. The discrepancy in energy demands between the sexes generally allows males to copulate indiscriminately to increase their fitness, while females are restricted by the costs of reproduction and are more selective [7], [8]. In spite of retaliation by social partners, females often continue to seek EPCs, suggesting EPP confers advantages [14]
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