Guppies occupy consistent positions in social networks: mechanisms and consequences

Abstract

The social network approach has focused increasing attention on the complex web of relationships found in animal groups and populations. As such, network analysis has been used frequently to identify the role that particular individuals play in their social interactions and this approach has led to the question of whether, and in what context, individuals consistently occupy certain positions within their network. Here we investigated the social networks of guppies, Poecilia reticulata, in the wild and tested whether 1) individual fish occupy consistent positions in their network and 2) whether these positions are robust to experimental manipulations to their habitat. Our habitat manipulations involved increasing and decreasing the surface area of their pools as well as translocating an entire pool population between different pools in situ. We found that guppies did indeed consistently occupy positions within their social networks, irrespective of the type of manipulation and that individual network positions vary between individuals. Our results suggest that at least 2 factors contribute to the observed individual variation in network position including 1) the tendency to be social and 2) sex-specific social preferences. Finally, we used a simulation to explore the implications of individuals consistently occupying different network positions regarding the exposure of fish to parasites and predators. The time until infection decreased with increasing rank of individual betweenness and the predation risk increased with decreasing rank of the individual node strength thus illustrating the potential ecological and evolutionary consequences of consistent network positions.