Geographic variation in advertisement calls of Crinia signifera (Anura:Myobatrachidae) in the Bass Strait area of south-eastern Australia

Abstract

The structure of recorded advertisement calls of a total of 176 males of Crinia signifera from eight localities on the south-eastern Australian mainland and Tasmania was investigated. On the basis of number of pulses per call (samples from all localities) and call duration adjusted to 13.0°C (samples from six localities), two geographic groups are recognised: (1) south-central Victoria, and (2) the extreme south-eastern mainland and Tasmania. This pattern of variation is postulated to reflect expansion of a differentiated Tasmanian stock on to the extreme south-eastern Australian mainland along the eastern sill of the Bassian Isthmus during the lower sea levels of the Late Pleistocene. Geographic variation in pulse rate (derived from number of pulses and call duration) was also considered because of its use in previous studies. The variation in dominant frequency in samples from five localities, adjusted for snout–vent length, does not conform to that for number of pulses and call duration, and is attributed to differences in demographic structure and recruitment.