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.”
Those snippets are from wikipedia’s article on parthenogenesis in reptiles. The Reptile Database provides more information on the ancestral species if you’re curious.
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.”
Glen Chilton: The Last Place You’d Look for a Wallaby. UQP, 2013
Glen Chilton was a Canadian when he started writing this book but now lives in Townsville and works at JCU. His main interest is birds and his first book, The Curse of the Labrador Duck, was about a crazy search for the last traces of a recently-extinct species. This time he criss-crosses the world to bring us tales about animals and plants in the wrong place, introduced deliberately or accidentally to new locations.
Australians know a fair bit about that sort of thing, of course – rabbits, foxes, cane toads, prickly pear and other pests have made sure of that – but the title story is about one of our exports: ‘the last place you’d look for a wallaby’ is on an island in the middle of Loch Lomond but that’s where the book begins. The wealthy, titled owner of the island released some red-necked wallabies there in the 1970s with a wildlife park in mind, and they survived and bred there quite happily without doing any great harm to the local environment.
Most introduced species, however, experience a population boom or bust in their new location, often rather quickly. And if the new location is successful – from the point of view of the introduced species – the effect on the local environment may be positive, neutral or negative.
Chilton tells us about all kinds of outcomes. Eucalypts are doing well in Ethiopia and are a vital resource to the local people; Pacific oysters are displacing local shellfish in the waters off Holland and elsewhere; Formosan termites are eating their way through New Orleans; Ruddy ducks from North America are interbreeding with a local Spanish species and may wipe it out unless current control efforts succeed; and so on.
The take-home message is that introductions can have wildly unpredictable consequences and may well be disastrous so avoiding them is good sense. But Chilton doesn’t preach. Indeed, he wraps his expert knowledge in so much lively anecdotal material that his message is in danger of being missed. His style has been compared to Bill Bryson but it reminded me most strongly of Douglas Adams’ Last Chance to See – solidly grounded in the facts but, above all, readable and entertaining.
The Last Place You’d Look for a Wallaby was launched at Mary Who? Bookshop in Flinders St on 22 February and will be the subject of the next Book Club meeting at the same venue, in the second week of April; contact the bookshop for details if you would like to attend.