STRUCTURE AND DYNAMICS OF A NARROW HYBRID ZONE BETWEEN GEOCRINIA-LAEVIS AND GEOCRINIA-VICTORIANA (ANURA, LEPTODACTYLIDAE) IN SOUTHEASTERN AUSTRALIA

A transect was established across the hybrid zone between Geocrinia laevis and G. victoriana near its southern (coastal) limit. Three diagnostic components of the phenotype, breeding-call structure and two muscle protein systems, were used to analyse the interaction between these parapatric, morphologically- similar species. The zone, based on breeding-call structure, is narrow (9-30 km), with most of the replacement occurring over 2 km. Contact samples consist of putative parental individuals and recombination products, so that this section of the zone may be described as an overlap with hybridisation. This contrasts with an earlier analysis of a transect near the northern (inland) limit of the zone, where there is a narrow intergradation with hybrids predominating in the replacement populations. In the southern transect, the two muscle protein systems have much broader zones of replacement than that for breeding calls (minimum widths of 33 and 72 km). The muscle protein zones are in different geographic positions from each other, and there is little overlap with the zone based on breeding calls. The patterns of replacement of the three characters in these species appear to be independent of one another, and emphasise the complex nature of hybrid zones. © 1979 The Genetical Society of Great Britain.