Functional diversity among grass species: the role of photosynthetic pathway

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One of the major unresolved problems in contemporary ecology is to understand how diversity arises in plant function. This has important implications for interpreting global patterns of biodiversity and predicting the impacts of climate change. In this application, we propose to investigate the factors responsible for the diversity of growth traits among the world's grass species, addressing the question of why different species grow at different rates, and allocate different amounts of growth to roots vs leaves. We are particularly interested in the role that has been played by evolutionary transitions between the C3 and C4 photosynthetic pathways. The C4 pathway is classically thought to boost the growth of plants under hot conditions, in comparison with the C3 type. Photosynthetic pathway is a major axis of variation in plant function that has been invoked to explain significant changes in ecosystem structure in response to past episodes of climate change, the turnover of grass species composition along global climatic gradients, and the ecological sorting of species within regional floras. However, recent work has challenged these long-standing interpretations by demonstrating that ecological adaptation to temperature and drought, and evolutionary history may each play an equally important role in explaining large-scale biogeographical and ecological patterns. In combination with intriguing recent experiments, these new findings raise questions about the extent to which C4 photosynthesis interacts with other plant traits, ecology and evolutionary history to influence plant growth. We will address these major issues by taking a comparative screening approach to investigate the growth traits of ~400 species under a range of environmental conditions. The use of large species samples will allow us, for the first time, to unravel the interacting roles of multiple factors within a unified framework. This approach has been opened up through significant recent conceptual and methodological advances in a number of areas, and represents a major step in the fusion of the fields of ecological and evolutionary informatics.