Recently, results of biophysical analyses performed by the group of Prof Michel Milinkovitch made the buzz as the researchers discovered that chameleons shift colour through active tuning of a lattice of guanine nanocrystals within specialised skin cells rather that by dispersion/aggregation of pigments.
While investigating this biophysical process in panther chameleons (Furcifer pardalis), Prof Milinkovitch and his students additionally decided to analyse the very large intra-specific colour variation observed in that species. They travelled to Madagascar and teamed up with Prof Achille Raselimanana, professor at the university of Antananarivo.
Raselimanana is also president of the Association Vahatra which aims at developing a research and teaching program that would help conserve the threatened biodiversity of Madagascar. The Swiss-Malagasy team performed two campaigns across the whole range of the panther chameleon distribution and sampled a drop of blood from each of 324 individual chameleons. Each sampled animal was also photographed with a high-resolution camera.
The researchers then conducted genetic analyses using the DNA extracted from the blood samples and performed mathematical analyses (using a so-called supervised multiclass support vector machine approach) of the colour pictures taken on the field.
The results of these genetic investigations – recently published in Molecular Ecology – indicates strong genetic structure among geographically-restricted lineages, revealing very low interbreeding among populations. In addition, the mathematical analyses demonstrated that subtle colour patterns could efficiently predict assignment of chameleon individuals to genetic lineages, confirming that many of the geographical populations might need to be considered separated species. Not only is this study revealing hidden biodiversity and suggesting taxonomic separation of the panther chameleon into multiple species thanks to the genetic data, but it also allowed the conversion of the mathematical analysis of skin colours into a simple visual classification key that can assist local biologists and trade managers to avoid local population over-harvesting.
Madagascar is a biodiversity hotspot, i.e. among the most diverse places for life on Earth. Indeed, Madagascar hosts at least 15’000 species of plants, 300 species of birds, 300 species of amphibians, 400 species of reptiles (including 85 species of chameleons), and 100 species of freshwater fish, without even considering the thousands of invertebrate species. In addition, approximately 80 to 90% of all living species found in Madagascar are endemic, meaning they exist nowhere else on earth.
This diversity is at great risk because of the widespread destruction of the forest habitat for firewood and charcoal production. Given the charismatic nature of chameleons, Prof Milinkovitch hopes that, beside a better understanding of the genetic basis of colour variation among chameleons, his collaborative study with Raselimanana will help his Malagasy colleague to continue raising awareness for the staggering but fragile biodiversity hosted by Madagascar.