Species diversification and differentiation in Madagascar and Indian Ocean Islands
Joeri Strijk supervised by Prof. Christophe
Thébaud and Dr Jérome
University Paul Sabatier (Toulouse III), Evolution and Biological Diversity Laboratory
The project will compare patterns of colonization and diversification in plant lineages occurring in the Biodiversity Hotspot covering Madagascar and the Indian Ocean Islands. Within this Biodiversity Hotspot an astounding diverse flora can be found, of which more than 11.000 species occur nowhere else. With close to 10% of the original vegetation cover remaining, the situation is critical for plants, and the animals depending on them. If we are to preserve biodiversity it is essential to understand the historical processes that have led to the patterns witnessed today.
The main element of this study will be to infer what the causes are for speciation and endemism, and why patterns vary for lineages and geographical areas. A combination of molecular data (markers ITS, ETS, rbc L and trn L-F) and morphological data (leaves, herbarium specimens) will be used in phylogenetic analyses and morphometric comparisons. The taxa under study encompass speciose genera with high numbers of single-island endemics ( Tambourissa (Monimiaceae), Gaertnera (Rubiaceae) and Psiadia (Asteraceae) ), genera with only one single-island endemic per island ( Pleurostylia (Celastraceae) and Gastonia (Araliaceae) ) and monospecific non-endemic genera (e.g. Aphloia (Flacourtiaceae)). By using distribution and ecological data available on another volcanic archipelago (Hawaii) it will also be possible to study the patterns of diversification on isolated island systems on a larger scale, and test whether there are commonalities in the patterns of speciation and island occupation, in terms of species as well as environment.