Chromosomal evidence for a hybrid origin of diploid parthenogenetic females from the unisexual-bisexual Lepidodactylus lugubris complex (Reptilia, Gekkonidae)

Chromosome banding analysis of seven diploid parthenogenetic females from Polynesian and Southeast Asian populations of the unisexual-bisexual Lepidodactylus lugubris complex (Reptilia, Gekkonidae) showed that the unisexual karyotype consists of two different haploid sets. Similar analysis of an L. lugubris male from a bisexually reproducing population revealed two identical chromosome complements, the banding pattern generally matching that of the females, although many chromosomes were obviously different. These observations suggest that the gonochoristic males belong to a taxon related to the parthenogenetic female taxon but are not a direct ancestor of the latter. The data also offer strong evidence for a hybrid origin of diploid parthenogenetic females in L. lugubris and suggest that a high degree of chromosomal heterogeneity may be the leading reason for the evolutionary selection of a modified meiotic process in this species, allowing production of unreduced oocytes and, consequently, of a unisexual mode of reproduction.