The research interests of my group centre on the evolutionary biology of snakes, particular venomous species. Particular emphasis has been placed on the following:

• Origin and evolution of venom in snakes. Venom is widespread among advanced snakes, irrespective of whether or not they are dangerous to humans. However, the origin of  the venom apparatus is less clearly understood: did venom evolve once at the base of the advanced snake radiation, and then become lost in some lineages, or did venom evolve multiple times independently in different lineages? Evidence from phylogenetic studies of advanced snakes supports the former hypothesis, but what about the venoms themselves? In collaboration with Bryan Grieg Fry (AVRU, University of Melbourne, Australia), we are analysing toxin gene families to determine whether there is evidence for a single recruitment of individual protein families at the base of the advanced snake radiation, or multiple independent recruitments in different snake lineages. In particular, we are focusing our attention on the hitherto neglected venoms of the medically insignificant, rear-fanged "colubrid" snakes. Early results support an early recruitment of several toxin gene families which are shared between multiple basal snake lineages. 

• Evolution of variation in venom composition and its consequences. Venom variation at all taxonomic levels is a ubiquitous feature of venomous snakes. I am interested in understanding the forces that drive the evolution of this variation. Work on Calloselasma rhodostoma has shown that venom variation is associated with geographic variation in diet (Daltry et al., 1996). We are now attempting to understand whether this is a general pattern in venomous snakes by repeating these experiments on other species groups. Variation in venom composition can have serious medical implications. We are working on the determination of the extent to which intraspecific venom variation is likely to compromise the effectiveness of available antivenoms.

• Neotropical biogeography. Using several groups of Neotropical pitvipers (Bothrops, Crotalus durissus) as model organisms, we are also seeking to understand general aspects of the biogeography of South America. Specific questions include the origin of patterns of diversity, both in species numbers and in terms of morphological diversity, in South American pitvipers, the role of  the uplift of the Andes in causing present patterns of diversity, the role of Pleistocene climatic changes in causing genetic structuring among present-day rainforest snakes, and the respective role of habitat diversity vs. Pleistocene vicariance in causing morphological divergence. We use a hypothesis-testing approach: we formulate predictions for patterns of variation due to hypothetical biogeographical scenarios, and then test our observed data against these predictions by means of tree topology comparison tests and Mantel matrix correspondence tests.

• Systematics of several species complexes of snakes: fer-de-lance (Bothrops atrox complex), western rattlesnake (Crotalus viridis complex), Neotropical rattlesnakes (Crotalus durissus), Asiatic cobras (Naja naja complex), African cobras (Naja spp.), New Guinea blacksnakes (Pseudechis spp.). The work consists of the diagnosis of species boundaries by means of multivariate analysis of morphological characters, as well as phylogenetic analysis of mitochondrial DNA sequences and AFLP analysis.

• Evolution of natural history and morphological traits. Molecular phylogenies allow the tracing of the evolution of morphological and natural history characters, and allow the testing of hypotheses on their origin. Current studies include the evolution of morphological adaptations in arboreal pitvipers, and the evolution of defensive adaptations in Asiatic cobras.

Individual projects include the following:

Systematics and phylogeography of the Bothrops atrox complex. In collaboration with Instituto Butantan (São Paulo, Brazil), Fundación Herpetológica Gustavo Orcés (Quito, Ecuador), Liverpool School of Tropical Medicine (Liverpool, UK) and Centre for Tropical Medicine, University of Oxford (UK)
 
 

  Systematics and Phylogeny of Asiatic cobras, with particular emphasis on the evolution of defensive adaptations. See also the Asiatic Cobra Systematics Page
 
 
 

Systematics of African cobras. Concentrates on species-level systematics of the major groups of African cobras (N. nigricollis group, N. melanoleuca, N. haje group). Description of new species of spitting cobra, Naja nubiae. In collaboration with Donald G. Broadley, Biodiversity Foundation for Africa, Bulawayo, Zimbabwe.
 
 
 

Phylogeography and systematics of the western rattlesnake (Crotalus viridis). With Catharine Pook.
 
 
 
 

Venom evolution and phylogeny in Elapid snakes. With Bryan Grieg Fry, Dept. of Pharmacology, University of Melbourne, and National University of Singapore, Atheris Laboratories in Geneva, Switzerland.
 
 
 

Phylogeography and systematics of the Neotropical rattlesnake (Crotalus durissus). With Ph.D. student Adrián Quijada. In collaboration with Dr. Maria da Graça Salomão (Instituto Butantan).
 
 
 

Systematics of Pseudechis. In collaboration with Mark O'Shea (West Midlands Safari Park), David Williams (James Cook University, Townsville, Australia) and Ilaiah Bigilale (National Museum of Papua New Guinea, Port Moresby, PNG).
 
 
 

Systematics of indigo snakes (Drymarchon). Description of a new species from Venezuela. See Indigo Snake Systematics Page
 
 
 
 

Funding

The research mentioned here has been funded variously by The Wellcome Trust, BBSRC, NERC, the Leverhulme Trust and the European Union, with additional support from the British Council, the Carnegie Trust, FAPESP and Fundação Banco do Brasil