The Litoria ewingi Complex (Anura: Hylidae) in South-Eastern Australia VII.* Mating Call Structure and Gentic Compatibility across a Narrow Hybrid Zone between L. ewingi and L. parawingi

Abstract

On the basis of the number of pulses per repeated note and of repeated notes per call for individual males, the interaction between Litoria ewingi and L. paraewingi in the region of the Tallarook (northern) transect is interpreted as a transitional hybrid zone, with populations consisting of hybrids and individuals of only one or other parental species. The Tallarook transect thus differs from the Glenburn (southern) transect, which is considered to be an overlap of both parental species together with recombination products. The minimum width of the zone in the area of the Tallarook transect is estimated to be 25 km, compared with 5 km for the Glenburn transect. Levels of partial and total anophthalmia were assessed in progeny from in vitro crosses involving a total of 27 males from both transects whose calls had been recorded and analysed, and females of L. ewingi from adjacent allopatry (a measure of the genetic representation of L. paraewingi). The results are, with one exception, consistent with the mating-call structure of these males. As was found with the Glenburn transect, calls of males of L. paraewingi from an allopatric population on the Tallarook transect close to the zone of interaction are more distinctive from calls of L. ewingi in pulses per repeated note than are those of distant allopatric populations of L. paraewingi. This finding is consistent with the suggestion that the products of reinforcing selection may be accumulating near the zone of interaction.