Dispersal of the Australian Reptile Tick Aponomma Hydrosauri by Host Movement.

Abstract

Tape recordings of calls of males in allopatric populations of the sibling species Ranidella insignifera and R. pseudinsignifera show non-overlapping ranges of call modulation. Laboratory-raised hybrids have a call structure falling between the high modulation of the three- or four-pulsed call of R. pseudinsignifera and the low modulation of the almost unpulsed call of R. insignifera. However, hybrid calls could not always be distinguished from some calls of the parental species. The largely allopatric distributions of the two species meet along the scarp of the Darling Ranges. In two areas examined in detail, west of Perth and north of Bullsbrook, populations sampled by ear and by tape recording confirmed earlier studies which suggested that there is a very steep cline, over less than 3 km, from populations with mostly R. pseudinsignifera-like calls, to populations with mostly R. insignifera-like calls. Populations with calls of both parental species as well as intermediate calls were detected in this zone, but the extent of introgression could not be judged on the basis of call structure alone. The evidence suggests that the hybrid zone is stable in time.