John Llewelyn

Email:
Phone: 0429 506956
Location: ATSIP Building, James Cook University, Townsville QLD 4811

Current Research

Although I am interested in many aspects of biology, I am especially fascinated by herpetology and evolutionary biology. My interest in these two areas has led me to study the relationship between cane toads and amphibian-eating reptiles in North Queensland (Australia) for my PhD.

Most native reptiles die if they consume a cane toad. It is not surprising then that populations of many amphibian-consuming reptiles have been observed/reported to decline rapidly following cane toad invasion. However, many native species that are initially affected by cane toad invasion have managed to survive, and often thrive, in North Queensland despite the presence of cane toads for over 60 years. The persistence and success of these native species in this region suggests that these species can adjust to the presence of cane toads through learning and/or adaptation.

Since 2006 I’ve been studying cane toads, focusing on the interactions between the toxic invasive toad and native frog-eating predators. These predators are vulnerable to cane toads, as they can ingest a fatal dose of toxin if they attempt to consume a toad. Yet many of these predators have survived, and now thrive, in regions where toads have been abundant for decades. It turns out that a variety of mechanisms/strategies help toad-vulnerable predators persist following toad invasion. For example, some predators have developed an aversion to feeding on toads and/or a higher tolerance to the toad's toxins, whilst others had a pre-existing aversion and/or tolerance to the invader. Such “toad-adjustments” can involve both phenotypic plasticity (e.g., learning to avoid toads) and hard-wired adaptation. In addition to these findings, toad/predator interactions demonstrate the importance of biogeographic origin and evolutionary history in determining a native's vulnerability to an invasive; native predators with close ties to Asia (i.e., migrating in the last few million years) appear to be less vulnerable than their Australian-endemic counterparts, probably reflecting the predators' recent evolutionary exposure to toxic Asian bufonids. That is, the Asian ancestors of these predators were exposure to toads in Asia that possessed similar chemical defences to the American cane toad, and this exposure helped preadapt the predators to deal with cane toads.

I've enjoyed studying toads, and been fascinated by the insight this research has provided on the toad's complex impact, as well as on invasive/native species interactions and predator/prey interactions more generally. Over the coming years, I will be broadening the scope of my research as I begin (mid 2011) a postdoc studying diversity in climatic adaptation within and between populations. In this research, I will be assessing the ability of populations to adapt to climate change, and the potential to enhance this adaptability through genetic translocation.

Past Research

During my Honours year (2002-03) I studied the thermal biology, circadian rhythm and diel activity patterns of several elapid snake species. The species studied varied with regard to activity time (e.g., nocturnal, diurnal) and included: the eastern small-eyed snake, the yellow-faced whip snake, the golden-crowned snake, the marsh snake, the broad-headed snake, the bandy-bandy snake and the red-bellied black snake. See below for further details.

Honours Research 2002-03

The thermal regime offered in a particular environment varies on a daily scale with diurnal temperatures higher and more heterogenous than nocturnal temperatures. Elapid snakes are a group of ectotherms that exploit different activity times.

I am interested in understanding the differences in the physiology and thermal biology of diurnal and nocturnal elapid snakes that allows them to be active in different thermal environments.

The species that I am studying include two nocturnal species, Eastern Small-eyed (Rhinoplocephalus nigrescens,above left), Golden Crown (Cacophis squamulosus), one species that is active nocturnally and diurnally, Swamp Snake (Hemiaspis signata,right), and one diurnal species, Yellowfaced whip-snake (Demansia psammophis,bottom). These species are similar with respect to diet, size, and they are all common in the Sydney region.

Education

Publications