Structure of Advertisement Call of Litoria ewingi (Anura: Hylidae) Introduced into New Zealand from Tasmania

Abstract

characteristics of repeated notes in the advertisement calls (duration, pulses per note, pulse rate, and dominant frequency) of frogs from the three islands were compared. Two significant differences were obtained: a higher variance in pulse rate (about three times) in the sample from South Island when compared with that from Tasmania; and a higher mean number of pulses per note in the sample from North Island when compared with that from South Island. These results indicate that some divergence has already occurred in the advertisement calls of both populations of L. ewingi in New Zealand (111 years after the establishment of the species on South Island, and 38 years after its successful transfer from South Island to North Island). As the advertisement call is a major component of the mating system of anurans, these findings are of considerable relevance to the allopatric origins of homogamy and provide an absolute time scale for the differentiation.