MORPHOMETRIC ANALYSIS OF A HYBRID ZONE IN GEOCRINIA - LARVAL VERSUS ADULT CHARACTER SUITES (AMPHIBIA, ANURA, MYOBATRACHINAE)

The southeastern Australian frog species Geocrinia laevis and G. victo riana have distinctive advertisement calls, yet form narrow hybrid zon es. Studies of allozyme variation indicated random mating in hybrid po pulations and revealed a peculiar pattern of steep, staggered dines in the frequencies of some marker proteins. To compare morphometric data with genetic and acoustic results, we measured two character suites: external morphology of tadpoles raised from field-collected egg masses and skeletons of adult males collected in the field. Larvae of G. lae vis had wider interpupillar distances but smaller oral disks with fewe r oral papillae than similar-sized tadpoles of G. victoriana. In adult frogs, the longer and narrower skulls and relatively longer urostyles of G. laevis differentiated it most from G. victoriana. Both larval a nd adult morphological traits showed fairly smooth transitions across the hybrid zone. However, for larval characters most hybrid population s resembled G. laevis, whereas in osteological features hybrids were o ften more similar to G. victoriana.