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Vries, 1995; also see Methods). Although they are not identical, the two indices generally yield the same values (see Methods; de Vries 1995) describing the degree to which an animal group adheres to a strict linear hierarchy. Thus, these indices are commonly referred to as metrics of 'linearity'. A major limitation of linearity indices is that they become biased when some pairs of individuals fail to interact (de Vries, 1995; Klass and Cords, 2011). This bias arises in part because strict linear hierarchies can occur only in groups where dominant-subordinate relations exist for every dyad in the group. Networks in which all dyadic relations are asymmetrical (e.g. dominant-subordinate) are called 'tournaments' (Harary & Moser 1966). However, tournaments rarely arise naturally in animal groups, and as we will show, unknown dyadic relationships are common because certain pairs of individuals fail to interact (hereafter 'null dyads'). Currently popular

In the long-tailed manakin (Chiroxiphia linearis), a long-lived tropical bird, early connectivity within a social network predicts male success an average of 4.8 years later. Long-tailed manakins have an unusual lek mating system in which pairs of unrelated males, at the top of complex overlapping teams of as many as 15 males, cooperate for obligate dual-male song and dance courtship displays. For as long as 8 years before forming stable ''alpha-beta'' partnerships, males interact with many other males in complex, temporally dynamic social networks. ''Information centrality'' is a network connectivity metric that accounts for indirect as well as shortest (geodesic) paths among interactors. The odds that males would rise socially rose by a factor of five for each one-unit increase in their early information centrality. Connectivity of males destined to rise did not change over time but increased in males that failed to rise socially. The results suggest that network connectivity is important for young males (ages 1-6) but less so for older males of high status (ages 10 -15) and that it is difficult to explain present success without reference to social history.delayed benefits ͉ lek behavior ͉ mating success ͉ network models ͉ social status

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The processes of adaptation and speciation are expected to shape genomic variation within and between diverging species. Here we analyze genomic heterogeneity of genetic differentiation and introgression in a hybrid zone between two bird species (Manacus candei and M. vitellinus) using 59 100 SNPs, a whole genome assembly, and Bayesian models. Measures of genetic differentiation (F ST ) and introgression (genomic cline center [a] and rate [b]) were highly heterogeneous among loci. We identified thousands of loci with elevated parameter estimates, some of which are likely to be associated with variation in fitness in Manacus populations. To analyze the genomic organization of differentiation and introgression, we mapped SNPs onto a draft assembly of the M. vitellinus genome. Estimates of F ST , a, and b were autocorrelated at very short physical distances (< 100 bp), but much less so beyond this. In addition, average statistical associations (linkage disequilibrium) between SNPs were generally low and were not higher in admixed populations than in populations of the parental species. Although they did not occur with a constant probability across the genome, loci with elevated F ST , a, and b were not strongly co-localized in the genome. Contrary to verbal models that predict clustering of loci involved in adaptation and isolation in discrete genomic regions, these results are consistent with the hypothesis that genetic regions involved in adaptive divergence and reproductive isolation are scattered throughout the genome. We also found that many loci were characterized by both exceptional genetic differentiation and introgression, consistent with the hypothesis that loci involved in isolation are also often characterized by a history of divergent selection. However, the concordance between isolation and differentiation was only partial, indicating a complex architecture and history of loci involved in isolation.