It takes two to tango: reproductive skew and social correlates of male mating success in a lek-breeding bird

Abstract

Variance in reproductive success among individuals is a defining characteristic of many social vertebrates. Yet, our understanding of which male attributes contribute to reproductive success is still fragmentary in most cases. Male-male reproductive coalitions, where males jointly display to attract females, are of particular interest to evolutionary biologists because one male appears to forego reproduction to assist the social partner. By examining the relationship between social behaviour and reproductive success, we can elucidate the proximate function of coalitions in the context of mate choice. Here, we use data from a 4-year study of wire-tailed manakins (Pipra filicauda) to provide molecular estimates of reproductive skew and to test the hypothesis that male-male social interactions, in the context of coordinated displays, positively influence a male's reproductive success. More specifically, we quantify male-male social interactions using network metrics and predict that greater connectivity will result in higher relative reproductive success. Our data show that four out of six leks studied had significant reproductive skew, with success apportioned to very few individuals in each lek. Metrics of male social affiliations derived from our network analysis, especially male connectivity, measured as the number of males with whom the focal male has extended interactions, were strong predictors of the number of offspring sired. Thus, network connectivity is associated with male fitness in wire-tailed manakins. This pattern may be the result of shared cues used by both sexes to assess male quality, or the result of strict female choice for coordinated display behaviour.

Male tolerance and male–male bonds in a multilevel primate society

“…In chimpanzees, maternal brothers affiliate and cooperate, but there also are a large number of affiliative and cooperative dyads that are unrelated or only distantly related, suggesting that cooperation provides direct benefits to the individuals (13). Fitness benefits associated with unrelated male coalitions also have been shown in Assamese macaques (33) and in several nonprimate species, including lions (Panthera leo) (34), and manakins (Pipra filicaudata) (35). Indirect fitness benefits also may play a role, however.…”

“…The results of the change-point analysis based on GPS data indicated that the Guinea baboon society consists of three structural levels. First, the algorithm detected a change point-reflecting dyads that associated more than 68% of the time (n = 12); these dyads were classified as belonging to the same "party," The mean party size was 25 individuals (range, [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. Second, we found a significant split separating dyads that spent up to 12% of the time together.…”

Proximity data-loggers increase the quantity and quality of social network data

“…Here, we advance our previous work on manakin social networks [5,6] by using a proximity logging approach to characterize weighted social networks. Two complementary measures of average network structure and topology suggest that males are both closely connected (path length) and highly clustered (clustering coefficient), with leks probably serving as densely interconnected neighbourhoods.…”

“…For example, wire-tailed manakins are cooperative lek-breeding birds that exhibit dynamic social behaviour in which territory males perform courtship displays alone, in a coalition with a non-territorial partner (floater), or in a coalition with another territory holder. Previous work using observational approaches has shown that display coalitions form the basis for complex networks and that network connectivity is a strong predictor of male fitness (social rise and reproductive success) [5,6]. Here, we test proximity data-loggers to quantify the frequency of social interactions, construct weighted networks and characterize variation in wire-tailed manakin social behaviour.…”

Understanding testosterone variation in a tropical lek-breeding bird

“…Specifically, male partners coordinate their display elements, and these partnerships provide benefits to both non-territorial males (increased probability of territorial inheritance [9]) and territorial males (increased reproductive success [10]). While the frequency of cooperative partnerships varies both within and among males of different social status [11], all males engage in these partnerships, as they are an essential component of male fitness [9][10][11]. However, despite the cooperative benefits of display coalitions, these partnerships are also thought to play an important role in the establishment of dominance hierarchies as males compete for social status.…”