Courtship and mating behaviour of the brilliant-thighed frog Allobates femoralis from Central Amazonia: implications for the study of a species complex

The identification of divergence in reproductive traits may substantially improve integrative approaches to understand species limits within clades that are suspected to contain cryptic diversity. The frog Allobates femoralis has been regarded as a pan-Amazonian species, and widely used as a model for addressing evolutionary issues regarding patterns of intraspecific diversification, social organisation, and animal communication. Recent accumulation of genetic, morphological, and bioacoustic data gathered from different localities strongly supports the idea that it represents a species complex, but field behavioural observations related to courtship and mating are surprisingly scarce. Here, we provide a description of several aspects of the reproductive biology of A. femoralis from a Central Amazon site, and compare our results with the few published reports for the species. This study demonstrated that, besides the known divergence in the number of notes of the A. femoralis call, there are both quantitative and qualitative differences regarding reproductive traits between two populations of this taxon. The most striking difference was the observation of cephalic amplexus in the population from the Reserva Ducke, Brazil, which contrasts with the absence of any kind of body contact between A. femoralis pairs during mating interactions at the Panguana Biological Station, Peru. In addition, we report for the first time a set of visual components of the courtship behaviour, such as throat display, limb lifting, circling, and leg stretching. Behavioural differences can lead to a pre-zygotic isolation, thus representing a first step in the speciation process through differential sexual preferences. Hence, our finding of divergence in a set of traits probably related to mate recognition and choice is surprising within populations assigned to a single clade, and highlights the importance of considering behavioural traits in order to disentangle the evolutionary forces driving the diversification of A. femoralis.