A phylogenetic tree showing the relative relationships of the major lineages with representative species for each lineage.
The evolution of the venomous function of snakes and the diversification of the toxins has been of tremendous research interest and considerable debate. It has become recently evident that the evolution of the toxins in the advanced snakes (Colubroidea) predated the evolution of the advanced, front-fanged delivery mechanisms. Historically, the venoms of snakes lacking front-fanged venom delivery systems (conventionally grouped into the paraphyletic family Colubridae) have been largely neglected. Isolation and characterisation by us of a potent postsynaptic three finger (3FTx) neurotoxin (alpha-colubritoxin) from Coelognathus radiatus (radiated ratsnake), an archetypal "non-venomous" snake species, forced a fundamental rethink of venom evolution. The toxin is homologous with the 3FTx previously thought unique to elapids and supports the role of venom as a key evolutionary innovation in the diversification of advanced snakes.. LC/MS (liquid chromatography, mass spectrometry) was used by us to analyse a large number of venoms from a wide array of species representing the major advanced snake clades. The results demonstrated a hitherto unsuspected diversity of toxins in all lineages, having implications ranging from clinical management of envenomings to venom evolution to the use of isolated toxins as leads for drug design and development. These studies thus provided a starting point for further research on snake venom evolution and potential clinical effects, but also is useful in biodiscovery.
The higher level relationships of the Colubroidea (Advanced snakes) are often misunderstood. Below is the taxonomical tree of the major families, with representatives shown. Points to notice are that the 'colubrids' do not exist as a natural group but rather are made up of by several families, some of which are vastly more closely related to the elapid snakes (cobras, death adders, mambas, etc.) than to corn snakes (which are in the family Colubrinae). Also, the sea snakes and sea kraits are not in their own families but rather are rooted deep within the Elapidae tree. The true sea snakes in fact are simply good little Australian snakes that had a day at the beach, liked it and never came home. At the end of the day they are simply highly modified Australian elapids, nothing more nothing less.
The venom gland was developed right at the very base of this tree, long before any of the 'colubrids' even showed up. Consequently, the vast majority of the advanced snakes are venomous, including most of the snakes typically thought of as non-venomous.
My research does not focus just on the evolution of snake venom but also on the evolution of the snakes themselves since the two are of course inextricably linked. I have a particular interest in how snakes have changed in time (as opposed to working on the current taxonomical relationships). We have been studying two lineages in particular, the death adders (Acanthophis) and black snakes (Pseudechis). These two genera are particularly interesting to us since they are widespread in both Australia and also New Guinea. We are tracing the genetic exchanges between Australia and New Guinea that have occurred as land bridges have developed. The results have been quite stunning and the paper should be out soon.
