I spotted this little lizard on the trunk of our poplar gum a fortnight ago and took photos because I had never seen one quite like it before. Its size (3.5 – 4 cm) and proportions told me it was only a baby, and its feet and smooth skin told me it was a gecko, but its markings are not at all like the two geckos we usually see here, the Dtella and its nearly identical Asian rival.
A little research allowed me to identify it as a Mourning Gecko, Lepidodactylus lugubris. Like our other geckos, the species is nocturnal, not very big (10 – 11 cm), and feeds on small insects. It also feeds on flower nectar; I’m not sure whether our others do that but it’s not unlikely.
Beyond that, the Mourning Gecko is an interesting little beast: it’s a hybrid, and it’s parthenogenic.
In other words, the ultimate ancestor of my little lizard was a female produced by the mating of two geckos of different species, and the family consists of an endless mother-daughter sequence. Adults are known to engage in female-female pseudo-copulation which apparently stimulates egg production, but even that is not necessary: one female on her own can and will lay viable eggs, usually two every few weeks.
As if that wasn’t strange enough, “The species consists of a number of clonal genetic lineages thought to arise from different hybridization events,” i.e. the ancestral species successfully hybridised on several different occasions, so there are variant ‘families’ of Mourning Geckos, each as closely related to the others as members of normal species are, but each producing a succession of genetically identical daughters.
But there’s more! “Surprisingly, parthenogenetic females of this species occasionally produce male offspring, which are thought to be the result of non-genetic hormonal inversions. While these males are anatomically normal, they produce abnormal sperm and are sterile.”
As Steve Wilson notes in A Field Guide to Reptiles of Queensland, the fact that it doesn’t need to mate to produce viable offspring has no doubt contributed to the Mourning Gecko’s success as an island coloniser, since a single stowaway can produce a whole new population. Wherever and whenever the species arose, it is now widespread across the islands and coastal areas of the Western Pacific and Indian Ocean.
It seems to be a very recent arrival in Australia. The distribution map at The Australian Reptile Online Database shows a coastal distribution in Queensland but Fitzsimons, in ‘Southward range expansion of the Mourning Gecko Lepidodactylus lugubris on mainland Australia and nearshore islands’ (2011, available here), goes into more detail. He analyses Australian records of the species to come to the conclusion that its range is extending southwards quite rapidly, from Port Douglas and Mission Beach to Townsville in the late 1990s and now Bowen, Gladstone and Heron Island. As he notes, this, “may be important for conservation, as the Mourning Gecko has the potential to compete with native Australian geckos.”