Genetic and morphological variation in Australian Christinus (Squamata : Gekkonidae): preliminary overview with recognition of a cryptic species on the Nullarbor Plain

Abstract

An allozyme electrophoretic analysis of the geographically widespread, southern Australian gekkonid lizard Christinus marmoratus demonstrates the presence of a hithertofore unsuspected, second species of Christinus. The second species, which was found to be syntopic with the 2n = 36 ‘race’ of C. marmoratus on the south-western side of the Nullarbor Plain, is strikingly cryptic and possesses a very similar 2n =36 karyotype. Small but consistent morphological differences between the two species allow their wider distributions to be mapped in detail. As the holotype of Phyllodactylus m. alexanderi Storr is identified as an example of the second species, Storr’s taxon is elevated to a full species and redefined. The geographic pattern of genetic variation within C. marmoratus crosses the distribution of the four recorded chromosome ‘races’. Reanalysis of previously reported reproductive data reveals likely differences in the timing of gametogenesis between C. alexanderi and the sympatric 2n = 36 C. marmoratus. Males of C. alexanderi show maximal testicular enlargement approximately six months before fertilisation, suggestive of oviducal sperm storage through winter, whereas the 2n = 36 C. marmoratus shows greatest testicular volumes at the presumed time of fertilisation. While females of both taxa carry eggs during September–October; C. marmoratus invariably carry two eggs, but C. alexanderi have a single egg in 36% of cases.