No abstract

Extrapair mating could drive sexual selection in socially monogamous species, but support for this hypothesis remains equivocal. We used lifetime fitness data and a unique model species, the dimorphic white-throated sparrow (Zonotrichia albicollis), to examine how extrapair mating affects the potential for sexual selection. In this species, the morphs employ distinct reproductive strategies, with white males pursuing extrapair mating at higher rates than tan counterparts. Social and extrapair mating is disassortative by morph, with paternity exchange occurring primarily between pairs composed of white males and tan females. Bateman gradients and Jones indexes indicated stronger sexual selection via mate numbers in white males than in females and tan males, and generally did not differ between females as compared with tan males. Extrapair mating contributed more to the Bateman gradient for white than tan males, and white males also had higher variance in annual reproductive success. However, variance in lifetime reproductive success did not differ between morphs or sexes. Moreover, extrapair mating did not increase variance in male reproductive success relative to apparent patterns, and within-pair success accounted for much more variance than extrapair success. Thus, extrapair mating by white males increases Bateman gradients and the potential for sexual selection via mate numbers. However, our latter results support previous research suggesting that extrapair mating may play a limited role in driving the overall potential for sexual selection.

No abstract

While the effects of 17α-ethinylestradiol (EE2) on male-typical behaviors are well studied, much less is known about the timing of these effects or the context in which these effects occur as most studies assay behavior at a single time point or in a single context. Additionally, exposure may affect behavior at levels beyond overall responsiveness, such as by altering behavioral consistency over time. Male threespine stickleback (Gasterosteus aculeatus) experienced three different contexts (single female, single male, paired female-male) over the course of 8 days, with an experimental group of males receiving EE2 after the first day. Exposure to EE2 disrupted responsiveness, behavioral consistency, and behavioral variation in all three social contexts. The timescale over which alterations in behavior occurred differed based on whether the conspecific was presented singly or paired with an opposite sex conspecific, stressing the importance of examining the effects of contaminants in multiple contexts.

Consistent individual differences in behavior suggest that individuals respond in a predictable and repeatable manner in a specific situation while differing from other individuals. Male Siamese fighting fish exhibit consistent individual differences in decision‐making strategies when they encounter a receptive female and a rival male simultaneously. However, whether these differences are altered by recent experience is unknown. We examined the influence of repeated aggressive encounters on behavioral consistency and decision‐making. Males were presented with paired female–male dummies prior to any aggressive experiences to obtain a baseline measure. Next, males either won or lost three consecutive contests against rivals and then received the paired female–male dummies after each of these encounters. Overall levels of highly aggressive behaviors were affected by contest outcome, while levels of female‐directed were not. Not surprisingly, winning a fight led to an increase in male‐directed bites, an overtly aggressive behavior that only occurs after fights have escalated. Fighting a male before encountering the dummies caused males to perform more tail beats to the dummy male, perhaps as a result of increased motivation. Males exhibited similar levels of repeatability and used the same strategies when faced with conflicting stimuli regardless of fighting experience. Thus, while winning or losing a fight impacts overall aggression, it does not influence behavioral consistency. This study demonstrates that consistent individual differences and decision‐making strategies may be resistant to recent aggressive experiences, even over a period of days.