5 Questions for… snake expert Sylvain Dubey
(December 3rd, 2013) Reptiles and amphibians are not everyone’s favourite animals. Ecologist Sylvain Dubey from the University of Lausanne is an exception. He’s one of the few scientists, who studies the genetic basis of colour variations in asp vipers.
Sylvain Dubey is a Swiss biologist with a passion for wildlife, particularly reptiles and amphibians. Studying these animals he seeks to understand basic issues of their ecology and evolution. In 2002, for instance, he worked on the conservation genetics of the European tree frog (Hyla arborea). Later he put up his research camp in Australia to provide scientific support to the conservation of several reptile species from the Blue Mountains World heritage area, west of Sydney. After obtaining a grant from the Swiss National Science foundation (SNSF), he moved back to his home country to start up his own research group at the University of Lausanne.
Lab Times: What is currently the main focus of your work?
My main project is focusing on the adaptive function of colouration in ectothermic vertebrates from an evolutionary and ecological point of view. But I’m also working on the conservation of different species and I’m engaged in various projects involving the ecology and evolution of vertebrates.
LT: What is – in your eyes - the most interesting aspect of your work?
It’s the complexity of the system leading to colour variations in organisms. Right now, I’d like to fully understand the role of colour polymorphism in the evolution of the asp viper (Vipera aspis), which is one of the most polymorphic species in the world. Interestingly, this species is able to live from sea level to more than 2000m above sea level, which is uncommon for reptiles. So, I want to understand if differences exist between colour morphs in terms of behaviour, (micro-) habitat choice, thermal requirements, and capacities to deal with environmental variations such as global warming. To date, we know that in montane areas there are differences in body condition [an assessment of the animal's weight for age and weight for height ratios, and its relative proportions of muscle and fat] between individuals of different colour morphs from the same population. Melanistic (dark-coloured), non-gravid females have a higher body condition than non-melanistic females. This difference is likely due to thermoregulatory advantages of being darkly coloured in cool areas. We also found that, within the same montane colour polymorphic population, melanistic and non-melanistic individuals are not randomly distributed. A larger proportion of melanistic individuals is at mid-elevation. So, there must be an advantage of melanism at mid-elevation, where forested (shady and cool) areas are predominant, compared with higher elevation sites, which are situated above the treeline and get more solar radiation. This pattern, however, could also be due to higher predation rates on melanistic individuals inhabiting open areas (without tree cover protection), where raptors are more common.
LT: In your most recent publication you report a link between the pro-opiomelanocortin (POMC) gene and colouration. Can you tell me a bit about this?
This is the first study showing a link between a gene and colour variations in a snake, the asp viper, as well as the first one showing a link between the POMC gene and colour variation in a wild vertebrate population. Such relationships were only known in humans and laboratory mice.
LT: So what is the big deal? Why is this important?
It’s important because studies focusing on colour polymorphism in wild population are scarce, despite the fact that it is crucial to understand the evolutionary processes maintaining colour polymorphism. Our study is not only important for this species but also for a large number of vertebrate species. Indeed, the POMC gene is highly conserved in vertebrates and is present in all classes (fish, mammals, birds, and reptiles), where it plays numerous functions. It also has biomedical implications because mutations at the POMC gene in humans are linked to disorders including atypical skin and eye pigmentation and to obesity and alcohol and drug dependence. As a consequence, any new study focussing on this gene is improving our understanding of these complex relationships.
LT: What are the next steps now?
The next step is to perform a comparative transcriptomic approach to investigate differences in the molecular network of asp vipers of different colour morphs. Here, the main goal is to understand the genetic processes leading to differences in colouration between individuals and to see whether there are differences in the expression of other genes, not involved in the production of melanin pigments, between the different colour morphs. Such analyses, coupled with field observations and experimental manipulations will allow us getting a clearer picture of the role of colour polymorphism in the evolution of these snakes.
Interview: Karl Gruber
Photo: S. Dubey