Structure and dynamics of mixed‐species choruses in a tropical anuran assemblage: insights from network analysis

Abstract

Males of a wide variety of vertebrates aggregate in mixed‐species choruses to attract females and signal territory occupancy. It is often assumed that species within these choruses co‐signal, interact and compete for the acoustic space, although few studies have tested this assumption, particularly in tropical and highly diverse environments. Using a novel combination of passive acoustics and network analysis, we monitored calling activity of a tropical anuran assemblage for an entire year and examined the structure and dynamics of mixed‐species choruses. Species composition was determined at 1‐min resolution on 288 recording hours and then used to estimate a set of centrality metrics (degree, strength and eigenvector) that characterize the species roles within the acoustic network. The studied assemblage formed a dynamic network comprising eight species during the rainy season and four during the dry season. These species showed distinct roles within the network, ranging from central species (those co‐signalling frequently and with many species) to peripheral species (those barely co‐signalling and with few species). Our results shed light on the species interactions in acoustic communities and challenge the general assumption of an equal contribution of species to the mixed‐species choruses. While in the rainy season the territorial frogs Boana albopunctata and B. faber exhibit the most prominent role within the network (with a higher degree, strength and eigenvector centrality), all of the species calling in the dry season co‐signalled with equal number of species, with only another territorial species, B. lundii, showing a higher rate of co‐signalling events (higher strength and eigenvector centrality). This suggests that territorial behaviour may favour increased calling activity and hence central roles in acoustic networks. These findings contribute to a better understanding of chorus dynamics in tropical assemblages and have crucial implications for the study of species interactions and the evolutionary hypotheses of acoustic divergence.