Supplementary information from "Geographic visual signal trends in neotropical frogs and their environmental predictors"

Visual signals are a widespread behavioral attribute of communication among vertebrates. This behavior is often utilized during intrasexual competition or to attract mates and is directly linked to reproductive success. However, information regarding the extrinsic factors driving the evolution of visual signals is generally lacking. Herein, we investigated trends of visual signal variation and the complexity in frogs related to humidity and vegetative heterogeneity throughout the Neotropical region. We constructed a dataset comprised of 236 frog species with visual signals in the Neotropical region based on a literature search. We performed spatial and phylogenetic regressions using potential evapotranspiration and canopy height as humidity and environmental heterogeneity proxies, respectively. Our findings indicate that species richness of frogs with visual signals tends to be higher in drier locations with more homogeneous vegetation. Spatial regressions showed that visual signal complexity tended to be higher in locations with more homogeneous vegetation. On the other hand, phylogenetic regressions showed that neither species richness with visual signals nor visual signal complexity were explained merely by environment. We suggest that frogs perform visual signals in drier locations with more homogeneous vegetation to maximize reproductive success with higher effectiveness of signal transmission while resources are available. Frogs with a more elaborated visual repertoire in locations with more homogeneous vegetation could be explained by selective forces, acting on individuals’ capability of communicating through a simpler background and reduced obstruction. However, the correlation of visual signals with frog richness followed by the absence of visual signal trends, considering evolutionary relationships, suggests that other factors should be considered to better predict visual signal trends. Given their remarkable behavioral diversity, frogs have the potential to serve as an excellent model for understanding visual signal evolution in vertebrates.