Release calls in anuran amphibians are emitted when a male is accidentally clasped by another male or when a female signals her unreceptive status to the male. However, it is not known how variable they are, and if they can display phylogeographic characteristics. The Mongolian toad, Pseudepidalea raddei, is one of the widespread species throughout whole Mongolia. Yet, no study on the release calls of this species has been conducted. We predicted no variation in release call properties, because it is not a trait affected by selection. We tested the null hypothesis of non-significant variation in relations calls by recording 34 male release calls at four different sites in northern Mongolia. The variables extracted here are the amplitude, intensity, energy and pulse and note lengths. We then checked for variations in release call properties based on geographical distances and morphological variations between sites. Using four fragments of partial mitochondrial DNAs (12S, 16S, COI and CR) isolated from 90 individuals of P. raddei sampled at different localities in Mongolia, we constructed phylogenetic relationships based on the Bayesian approach, in order to test the intraspecific genetic variations.
Results/Conclusions
The shape of each release call note between 34 male individuals, showing variations at oscillograms. Besides that, the F-values and P-values from ANOVA test prove that our null hypothesis, there are no significant differences in variables of the release calls among different study sites in Mongolia, is rejected. Furthermore, test of genetic variations using phylogenetic inference from mtDNAs indicates two clades segregate within the eastern and western populations of P. raddei in Mongolia. The intraspecific variations of the Mongolian toads insinuate local isolations based on landscape features, as the western Mongolia consists of mountainous areas and having colder temperature over the eastern part. Our finding proposes that the adaptive potential of the release calls of this species could be influenced by various factors such as regional variations, local adaptation or selection against predation. This study also opens the possibility of a non-described cryptic species in the Mongolian toads although, still unlikely.