DISSERTATION RESEARCH:Ecological interactions mediate the effects of climatic stress on populations: dissecting the direct and indirect effects of climate on plants

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Most projections of shifts in species distributions with climate change assume that geographic ranges are strongly determined by abiotic stresses including temperature and precipitation. However, ecologists have generally thought that species ranges in areas where such stresses are relatively low are strongly influenced by biotic interactions such as predation or parasitism. Though this long-standing hypothesis contradicts the assumptions behind most projections of future species distributions, there are few tests of the relative strength of abiotic and biotic interactions across meaningful portions of species ranges or along stress gradients. This project will use field and greenhouse experiments to assess the effect of pollination on performance of the common, understory plant Hibiscus meyeri along an aridity gradient in East Africa, adding to on-going studies of herbivory and interactions between plants in the same system. The work will help develop species distribution modeling by using H. meyeri to construct predictive distribution models that vary in their incorporation of multiple biotic interactions. Results will help to show when biotic interactions must be included to understand how species will be influenced by changes in temperature and precipitation.The broader impacts of this research include provision of scientific information for the conservation of biodiversity and national and international training for students and outreach to resource managers and users. Many pollinators and large herbivores are threatened in Africa and around the globe, and this work will help show the potential effects of their extirpation on the functioning of ecological systems. The project will train U.S. and Kenyan undergraduate students and a U.S. Ph.D. student, and collaborate with the National Museums and the Mpala Research Centre in Kenya.