Research Highlights
Sand dunes near Yulara, Northern Territory (Photo credit: Stephen Zozaya)
The biogeography of the Australian arid zone
Covid had us all stuck at home for much of 2020, and I used this time to finally sit down and collate information about what was known about the evolutionary history of Australia’s arid zone - what did the landscapes used to look like, when did they start to dry out, when were the deserts formed? The main message from our review is that for much of Australia's biota living in the broad centre of the continent, their deeper history was shaped by an environment characterized by vast fluvial systems, feeding enormous volumes of water into permanent mega-lakes and transporting large quantities of sand across the landscape. This extensive surface water dried out first in the west, and elsewhere fluvial systems switched to an ephemeral state and progressively became saline. But wet pulses in history would have reactivated these inland rivers from time to time as precipitation waxed and waned with glacial cycles (even during the driest period in the Last Glacial Maximum there were large rivers in the southeast and enhanced run-off from the highlands). When they were dry, their sand filled valleys could be blown out by wind, forming extensive sandplains across the continent that would have been stabilized by a vegetation progressively shifting to dry woodlands, and open shrublands and grasslands. Geochronological evidence suggests that the formation of dunefields began in the mid-Pleistocene, accelerating as the climate became increasingly arid in later glacial cycles. These dunes reflect episodic accumulation, and patchy, rather than widespread, activity, so the deserts in Australia never looked like the vast mobile dune landscapes of the Sahara. With this in mind, it becomes more apparent how species could have persisted and diversified in the arid zone despite the enormous and turbulent climatic changes of the Pleistocene. You can read an easy to understand blog post about the article HERE
Understanding phylogeographic structure of Australia’s iconic frill necked lizard
This was a fun paper to write. Despite being one of Australia’s most well-known lizards, I had only even seen frillies in the flesh on a golf course in Broome! As you can see from the map though, they are found all across northern Australia and down the northeast coast, and even into southern New Guinea . Despite the fact there is significant colour variation in the frill as you move from west to east (red, to orange, to yellow to white), there is little change in body proportion measures. We also found surprisingly little genetic variation across its distribution, a pattern which contrasts starkly to many other vertebrates across this part of Australia. Extremely low genetic diversity within each of the three clades over vast geographic areas is indicative of recent gene flow that we think was facilitated by widespread savannah during interglacials, or alternatively may reflect population bottlenecks induced by extreme aridity during Pleistocene glacials. The shallow divergence between Australian and New Guinean samples is consistent with recent connectivity between Australia and New Guinea that would have been possible via a savannah corridor across the Torres Strait. If you are interested in the mechanisms underlying the colour variation in frillies, check out some papers by Thomas Merkling and others who collaborated with us on this paper.
Platysaurus attenbouroughi from Namibia (Photo credit: Martin Whiting)
Phylogeny, systematics & taxonomy of the spectacular flat lizards of southern Africa
I have been lucky enough to work with Scott, Martin Whiting and 2 late greats of African herpetology, Don Broadley and Bill Branch, on understanding the relationships between species in this spectacular genus of lizards in southern Africa. They look like they have been painted by a 5yo who has had too much red cordial, and the colour variation across the group is absolutely mind blowing. They also are incredibly FLAT, owing to their highly specialised lifestyle on rocky outcrops that weather to produce narrow cracks and fissures that they shelter in. We have sequenced a number of genes to resolve the phylogeny of Platysaurus, and in doing so have identified a bunch of new species. We will describe these and also elevate others from subspecies. It’s been a painstakingly long road, but the end is in sight! And there will be amazing supplementary material which will have photos of all the males and females of each species, photos of habitat and species distribution maps - a one stop shop for anyone interested in Platysaurus. Watch this space.