We recently drove down the coast to Mackay, then inland and South to Carnarvon Gorge before returning home via Clermont and Charters Towers. I will write about Cape Hillsborough and the Gorge in due course but first I will share my overwhelming impression from the 1800 km, twenty hour, trip: it’s flat!
Really, really, flat!
We have known for a long time that Australia is flat – old, worn down, eroded, etc – but there’s a difference between book-knowledge and body-knowledge.
Where Did We Come From? is the title of a book written by Carl Zimmer in the wake of the discovery of the “hobbits” of Flores fifteen years ago. It was a very good popular introduction to human evolution.
According to Zimmer, our African ancestors parted company with the ancestors of chimpanzees and bonobos six or seven million years ago to begin developing an upright posture, tool use and, perhaps most importantly, language. Our own species, Homo sapiens, evolved about 200,000 years ago and began spreading out of Africa 130,000 years ago, through Europe, Asia, Australia and, eventually, America. We lived alongside closely related species until comparatively recent times. Neanderthals reached Europe before we did and coexisted with us there until 28,000 years ago, if not later. The ‘hobbits’ of Flores, by far the most spectacular recent discovery in the field, survived as recently as 18,000 years ago, well after Homo sapiens had migrated through South Asia and the islands to Australia.
Given the pace of discovery in the field, Zimmer’s book is now somewhat outdated. This collection of recent articles introduces research which adds depth and complexity to Zimmer’s account without changing its broad outlines. I have assembled them here in evolutionary order. Continue reading “Where did we come from?”
Midwinter, the winter solstice, doesn’t mean as much here in the tropics as it does further from the Equator but it’s still a significant turning point.
The winter solstice is always close to June 21 – 22, and this year’s was yesterday, June 21, according to this lovely site. (I chose it partly in memory of a warung (restaurant/cafe/bar) owner’s patient explanation of an amazingly detailed Hindu astrological calendar to me in Bali a year ago.)
According to this site, the solstice was not just generally “June 21” but specifically at 20:06:39. Sunrise was at 06:45:29 and Sunset at 17:43:38, for a Day Duration of 10 Hours 58 Mins 09 Secs. The previous day was 1 second longer and today was the same length as the solstice day.
Winter arrived yesterday, with its usual suddenness.
As in most years, a big weather pattern somewhere down South pushed cold, dry air from Central Australia out over the ranges to Townsville. Overnight temperatures dropped, and the humidity crashed. Last year I reckoned the Dry arrived at the end of April, as it did in 2014 and 2015 so we’re running a couple of weeks late this year.
In numbers, the changes are from overnight minimums of 18 – 21 C for the beginning of May down to 13.4 and 10.6 on the nights of the 12th and 13th, and humidity from 55 – 90% down to 16 – 19%.
In daily life that means the cat becomes a permanent lap-rug, if he can get away with it, but we’re not permitted to stroke him because sparks leap painfully from the tips of his ears and tail. Meanwhile, we search for windcheaters we haven’t worn for six months and seek out patches of sunshine in the morning instead of drifting automatically into shade.
Let me be clear, however: I am not complaining. I love this weather, and after a good Wet season I really look forward to it.
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.”