A single celled alga, (the diatom Stephanodiscus yellowstonensis) originated in Yellowstone Lake, Wyoming from about 12,000 to 8,000 years ago, apparently from its nearest relative, S. niagarae which lives in nearby lakes. The significance of the research goes far beyond a detailed description of diatom speciation. The proposed research speaks to a broad range of questions from factors controlling origin of new species to global climate change. The project integrates 3 lines of evidence: paleontological, morphological, and genetic. Sediment records from some of the largest high altitude lakes in the world (Yellowstone Lake and Jackson Lake in northwestern Wyoming and a series of lakes between them) will be collected. From these sediment records a detailed record of regional climatic change (using pollen, diatoms, oxygen isotope, grain size and other features as available) will be obtained. The information will be compared to an extraordinarily well detailed and CONTINUOUS record of this new species within a 4,000 year period (the early Holocene, a time of significant global warming). Among other results, we expect to obtain a detailed record of change in species as a response to entire ecosystem change in response to global warming. This study will help serve as a basis for predicting changes in the earth's biota in response to possible future global change, anthropogenic and/or natural.