The origin and evolution of parthenogenesis in Heteronotia binoei (Gekkonidae)

Abstract

Within Australia, the gekkonid lizard Heteronotia binoei exists as diploid bisexual and triploid all-female populations. Three bisexual cytotypes and three triploid clones can be described on the basis of the morphology of gross karyotypes. This paper reports the results of a C-banding analysis that revealed both intrapopulation polymorphism and interpopulation polytypic variation within the most widespread bisexual cytotype (A6). A C-band variant that defined a ZW sex chromosome system in populations from the MacDonnell Ranges in central Australia was also identified. Silver staining confirmed that in all populations the nucleolus organising region always occurred distally on chromosome 6. Examination of C-banding and silver-staining patterns of triploid populations provided strong support for a hybrid origin of the parthenogens that involved the central and western A6 populations. It is proposed that the hybridisation of these populations with the other chromosomally distinct bisexual cytotypes (SM6) resulted in the triploid clones. At present, seven clones have been karyotypically defined, and all the chromosomal variants that were present in the triploids can be accounted for by multiple hybridisation events between the bisexual populations. The analysis also provided evidence that rare sterile tetraploid females are the result of insemination of the triploid parthenogens by male H. binoei.