Social network analysis resolves temporal dynamics of male dominance relationships
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Social organization is often studied through point estimates of individual association or interaction patterns, which does not account for temporal changes in the course of familiarization processes and the establishment of social dominance. Here, we present new insights on short-term temporal dynamics in social organization of mixed-sex groups that have the potential to affect sexual selection patterns. Using the live-bearing Atlantic molly (Poecilia mexicana), a species with pronounced male size polymorphism, we investigated social network dynamics of mixed sex experimental groups consisting of eight females and three different-sized males over a period of 5 days. Analyzing association-based social networks as well as direct measures of spatial proximity, we found that large males tended to monopolize most females, while excluding small- and medium-bodied males from access to females. This effect, however, emerged only gradually over time, and different-sized males had equal access to females on day 1 as well as day 2, though to a lesser extent. In this highly aggressive species with strong social dominance stratifications, the observed temporal dynamics in male-female association patterns may balance the presumed reproductive skew among differentially competitive male phenotypes when social structures are unstable (i.e., when individual turnover rates are moderate to high). Ultimately, our results point toward context-dependent sexual selection arising from temporal shifts in social organization.
KeywordsSocial network analysis Phenotypic polymorphism Dominance hierarchy Atlantic molly Poecilia mexicana
We like to thank J. Appel, J. Hanisch, and M. Grothe for their assistance in the laboratory. Financial support came from the Deutsche Forschungsgemeinschaft (DFG; PL 470/1-3) as well as from the Leibniz Competition (SAW-2013-IGB-2).
The experiments reported here comply with the current laws of the United States of Mexico and were run under the federal permits from Mexican agencies SAGARPA/CONAPESCA (DGOPA.09004.041111.3088) and SEMARNAT/Directión General de Vida Silvestre (SGPA/DGVS/04315/1).
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