Structure And Dynamics Of Mixed-Species Choruses In A Tropical Anuran Assemblage: Insights From Network Analysis

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.