Molecular evidence of extra-pair paternity and intraspecific brood parasitism by the Magellanic Penguin (Spheniscus magellanicus)

Abstract

Molecular studies have shown that, although most avian species are socially monogamous, they can exhibit different reproductive strategies, such as extra-pair paternity (EPP) and intraspecific brood parasitism (IBP). We investigated the genetic mating system of the Magellanic Penguin, Spheniscus magellanicus, a species that is reported to be monogamous, with little or no evidence of extra-pair paternity, high partner faithfulness over the years and intense biparental care. Thus, we proposed that if EPP does occur, the rate will be low and could be related to increased genetic diversity among offspring or the body condition of parents. As a consequence, we hypothesize that offspring from EPP will exhibit faster growth than non-EPP offspring, thus increasing their survival probability. In contrast to expectations, EPP was detected in 31% of the offspring and 48% of the nests had at least one extra-pair young. In addition, 6% of chicks were not the offspring of the putative mother or either member of the social pair, indicating evidence of IBP. However, we did not find a difference in genetic diversity between nests with or without EPP, nor did we find differences in parent body condition. Offspring from EPP showed slightly faster growth than non-EPP offspring, although this difference was not statistically significant. These results reveal a high rate of EPP and a low rate of IBP, both of which were previously unknown for this species. Our findings demonstrate that the Magellanic penguin has a more complex social mating system than previously thought.