SG: Fossils, fruits, and seeds: an integrative approach to estimating a timetree for the nightshades

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Reconstructing the timing of evolutionary events, from the invasion of land to the origin of flowers, relies on evidence from the fossil record. For many groups of organisms, available fossils are scant or poorly described, resulting in uncertainty about when major evolutionary transitions occurred. This project will expand knowledge about the fossil record and estimate an evolutionary timeline for a large and economically important plant group, the nightshades. This family of nearly 3000 species includes many crops, such as tomato, potato, and tobacco, and yet is represented in the fossil record by only a handful of described specimens. The researchers will survey putative nightshade fossils and use morphological and statistical analyses to determine their placement in the evolutionary history of the family. In the process, the researchers will be able to estimate the timing of major evolutionary changes, such as the origin of fleshy fruits and whole genome duplications. Understanding this evolutionary history is fundamental for crop improvement, which relies on the morphological and genetic variation accumulated through diversification over millions of years. This project incorporates a range of training opportunities for early-career researchers, and the results of the research will be widely disseminated through public data repositories.Divergence times across the nightshades (Solanaceae) will be estimated through three specific aims. First, the researchers will revise all fossil records from the family and score a suite of discrete and continuous characters using traditional and newly developed techniques, including variable pressure scanning electron microscopy and x-ray microcomputed tomography. Second, a matching morphological dataset will be created for the roughly 1600 extant species with available molecular data from previous phylogenetic analyses. Finally, Bayesian total-evidence methods will be used to jointly estimate relationships among extant and extinct species and divergence times across the family. This integrative project will be carried out by a team of botanists, paleontologists, imaging specialists, and methods developers. In addition to estimating a robust timeline for Solanaceae, the project will expand knowledge of the plant fossil record, support training of undergraduate and graduate students and a post-doctoral researcher, as well as strengthen international scientific infrastructure and collaboration.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.