Evolutionary implications of advertisement call variation in Bufo debitis, B. punctatus, and B. retiformis

We examined variation in advertisement calls of Bufo retiformis and its relatives in Arizona, USA. Calls were recorded from three populations of B. retiformis, two populations of B. debilis, and three populations of B. punctatus. For B. retiformis, pulse rate and dominant frequency, but not call duration, were significantly related to temperature, and dominant frequency and pulse rate, but not call duration, were negatively correlated with snout-vent length. In spite of its larger size, advertisement call frequency of B. retiformis was similar to B. debilis. The relationship (i.e., slope) between snout-vent length and frequency, and the relationship between body temperature and pulse rate, were not equivalent for these three taxa. Pulse rise time was similar in B. debilis and B. retiformis, and significantly different between these taxa and B. punctatus. In contrast to the intermediate calls typical of hybrids between closely related bufonids, advertisement calls of a hybrid B. punctatus x B. retiformis were aberrant, but more similar to B. punctatus rather than intermediate to the parental forms. The call producing mechanisms of B. debilis and B. retiformis are not similar to B. punctatus, and in a phylogenetic context are probably plesiomorphic relative to those of B. punctatus.