Intra-specific variation of the call-body size relationship in an extensively distributed frog

Acoustic communication is a fundamental aspect of anuran reproductive behaviour, facilitating conspecific recognition and mediating intra- and inter-sexual interactions. The production and propagation of these signals are affected by environmental and constitutional factors. Among the latter, the relationship between body size and acoustic properties of anuran vocalisations has been studied across several taxa. In particular, an inverse correlation between body size and dominant frequency of calls prevails in many anuran species, so that larger individuals produce calls with lower dominant frequencies. Nevertheless, this allometric relationship has been explored to a limited extent at an inter-populational level within a species. The four-eyed frog ( Pleurodema thaul ) is extensively distributed in Chile, presenting geographical variation in the spectral and temporal characteristics of its advertisement call. We obtained data from 13 localities encompassing most of the species’ latitudinal range and evaluated the relationship between body size and dominant frequency within each population. Our analyses reveal that the allometric relationship does not follow a strictly uniform pattern at an intra-specific level, as not all populations comply with the negative correlation between these traits. The variability of this allometric relationship conforms with the lack of preferences for call spectral features in this frog and supports potential early evolutionary processes acting on the divergence of acoustic communication systems in anurans.