Breeding synchrony and extrapair paternity in a species with alternative reproductive strategies

Grunst, Melissa; Grunst, Andrea; Gonser, Rusty; Tuttle, Elaina

27 February 2017

Breeding synchrony may affect the tradeoff between pursuing multiple mates and avoiding paternity loss, translating into differences in the rate of extrapair paternity (EPP). However, diverse empirical relationships between breeding synchrony and EPP remain challenging to explain. We examined whether the relationship between breeding synchrony and EPP varied with male morph, age, body size, or breeding density in the white-throated sparrow (Zonotrichia albicollis). In this species, males of two genetically determined morphs pursue alternative mating strategies. Breeding synchrony positively correlated with EPP within polygamous white morph males, which have high rates of EPP and cuckoldry, but was unrelated to EPP within tan morph males, which prioritize mate guarding and paternal care. As previously reported, males that gained EPP were primarily white males. Males gained EPP more often than expected by chance during their mate’s fertile period and on neighboring territories. Since extrapair copulation appears primarily male-driven in this species, these results indicate that white males focus extra-pair mating effort during periods of high synchrony and during their mates’ fertile periods, even at the expense of paternity loss within their own nests. Breeding density, male age, and male size did not modify the relationship between breeding synchrony and EPP. However, older white males had higher cuckoldry rates, perhaps reflecting declines in performance associated with senescence. Results suggest that, even within species, mating strategy may modify how breeding synchrony affects rates of EPP, with positive relationships manifest only within subsets of individuals that pursue a strategy of polygyny at the expense of paternity loss.