Acoustic coummunication strategies in dendrobatid frogs

Signal detection and signal recognition are necessary for effective communication and, thus, vulnerable to the selective effects of interference by heterospecific signals. During a previous FWF project (BIO-15345), we have developed a successful research topic by studying both the sender and the receiver component of the male-male communication system of territorial dendrobatid frogs. Two main results constitute the starting point for this research proposal. First, we have evidenced geographic variation in the receiver but not the sender portion of the communication system of Epipedobates femoralis, indicating an effect of masking interference by E. trivittatus. Second, the recognition space has proven to be larger than necessary for the recognition of conspecific signals. The first part of this research proposal aims at developing the case for adaptation, by studying the factors that affect male reproductive success in E. femoralis, including an experimental test of the effect of masking interference by artificially introduced calls of E. trivittatus. To develop this idea we will combine behavioural studies in the field, experimental manipulation of the acoustic environment and parentage analysis with microsatellite markers. The second part of this research proposal aims at understanding the evolutionary forces that shape the recognition space, by testing its correlation with the probability of acoustic interference on a species-pair basis. To develop this idea we will conduct playback experiments of synthetically manipulated calls on five species of dendrobatid frogs as well as recordings of the acoustic environment at their calling positions. The development of this project should allow us to submit at least three manuscripts to international peer-reviewed journals, to contribute to the education of postgraduate (three master and one PhD) students, and to strengthen the scientific collaboration with international partners.

In the FWF-project 18811 we studied a wide range of topics in the biology of our model organism, the dart-poison frog Allobates femoralis. We considerably improved our knowledge on territorial behaviour, mating system and communication of the species, and investigated the effect of masking interference by heterospecific calls on territorial males. Furthermore, we explored evolutionary adaptations to heterospecific calls in a complex acoustic frog assemblage. One of the most striking results is the existence of a polygynandrous mating system in A. femoralis, i.e. both males and females mate and reproduce with several partners. Females try to increase their reproductive success with more partners, as territorial males are responsible for brood care in this species. Patterns of movements within and between reproductive seasons revealed that both females and males show a high degree of site fidelity during a reproductive period. Males give up their multi-purpose territories between reproductive seasons (= years) and thus they have to renegotiate territories each year. This leads to a distinct movement pattern for males between years, whereas females retain regional site fidelity. We learned that mainly differences in temporal call properties may enable acoustic discrimination of neighbours and strangers by territorial males, and that the accuracy of localising intruding males during phonotactical approach of the territory owner is mainly mediated by calling bouts. We broadcasted artificial calls of Ameerga trivittata to naive territorial males of A. femoralis to test the effect of masking interference of the frequency-overlapping calls of another frog species on the behavioural and reproductive performance of the males. The acoustic presence of A. trivittata led to larger territories and lower opportunities for mating and breeding in A. femoralis males. Here we show for the first time in anurans the commonly invoked negative effect of heterospecific masking interference on individual fitness in a species. Finally, we studied evolutionary adaptations in acoustic communication signals and signal processing traits in a complex acoustic assemblage of diurnally active frog species. In such noisy environments both signal space and recognition space in a species may be strongly shaped by heterospecific sound interferences. Spectral call properties contributed more than temporal properties to discriminate between species and species with similar call features did not show spatial or temporal segregation. Recognition spaces of species did not closely coincide with their signal spaces, but exceeded in most cases their natural range of variation. Although extent and symmetry of the deviations were highly variable among species, males generally tolerated wider temporal than spectral deviations, indicating a role of masking interference in shaping the recognition space.