Evolutionary implications of advertisement call variation in Bufo debilis,B-punctatus, and B-retiformis

We examined variation in advertisement calls of Bufo retiformis and its rel atives in Arizona, USA. Calls were recorded from three populations of B. re tiformis, two populations of B. debilis, and three populations of B. puncta tus. For B. retiformis, pulse rate and dominant frequency, but not call dur ation, were significantly related to temperature, and dominant frequency an d pulse rate,but not call duration, were negatively correlated with snout-v ent length. In spite of its larger size, advertisement call frequency of B. retiformis was similar to B. debilis. The relationship (i.e., slope) betwe en snout-vent length and frequency, and the relationship between body tempe rature and pulse rate,were not equivalent for these three taxa. Pulse rise time was similar in B. debilis and B. retiformis, and significantly differe nt between these taxa and B. punctatus. In contrast to the intermediate cal ls typical of hybrids between closely related bufonids, advertisement calls of a hybrid B. punctatus x B. retiformis were aberrant, but more similar t o B. punctatus rather than intermediate to the parental forms. The call pro ducing mechanisms of B. debilis and B. retiformis are not similar to B. pun ctatus, and in a phylogenetic context am probably plesiomorphic relative to those of B. punctatus.