Bright colour patterns as social signals in nocturnal frogs

Abstract

Some nocturnal animals are brightly marked, yet the adaptive significance of their colourful patterns in low light is poorly understood, and this phenomenon is particularly prevalent in amphibians. One way to resolve this seeming paradox is to determine whether these colour patterns serve as visual cues that evolve through sexual and/or natural selection. Accordingly, we focused on Central American phyllomedusines, a clade of leaf-frogs well known for variable and colourful markings. We first tested the null hypothesis that phylogeny explains colour pattern evolution and then tested for overdispersion in sympatry. Phylogenetic analysis confirms that colour pattern variation is not correlated with lineage diversification and tests of overdispersion show that colour patterns of closely related taxa diverge in sympatry. Combined, these evolutionary and community-based lines of evidence support the hypothesis that flank colour patterns probably function in species recognition. They are thus analogous to widespread visual displays among diurnal vertebrates, suggesting that the richness of similar sensory interactions among animals after dark might be severely under-appreciated.