Grass Evolution, Anti-Herbivory and Past Climate - COMPLETED 2008
Cortaderia sp. © S. Renvoize
The grass family Poaceae comprises more than 10,000 species and 700 genera. They include cereals such as wheat, rice, maize, sugar cane, millet and rye, as well as numerous forage grasses such as rye-grass, fescue and cocksfoot. Grasses occur on all continents and are ecologically dominant in many ecosystems such as the African and South American savannahs. The evolutionary success of the grasses in terms of species number might be due to their adaptability to changing environments. It has also been hypothesised that grasses and large grazing herbivores have co-evolved. Our aim is to obtain a comprehensive phylogenetic tree for Poaceae at a generic level and identify shifts in diversification rates among lineages. Then, we will evaluate whether specific morphological, chemical and anatomical traits correlate with anti-herbivore functions (silica body density, fibre content and rhizome biomass) for which data are already gathered from most of the taxa growing in the Grass Garden; some of these characters could have had an influence in the success of some grass species by conferring a higher resistance to herbivory and allowing open-habitat species to radiate. Other factors, such as the evolution to C4 photosynthesis in grasses during periods of time where climate changed (temperature, atmospheric CO2), are also under investigation.