The tallgrass prairie is an iconic American landscape dominated by a single group of grasses known as the Andropogoneae, which is responsible for much of the plant productivity world-wide. This group also characterizes the vast tropical grasslands of central Africa and Brazil and contains many economically important crop species, such as corn and sorghum. However, how this group came to dominate these habitats and diversify into approximately 1200 species is unknown. Species within the group have a range of floral architectures, which suggests that the evolution and diversification of this group may be influenced by the function of its reproductive structures. This project will test this hypothesis using comparative morphological and functional analyses of these reproductive structures in the context of the phylogeny of the Andropogoneae. The research plan incorporates a range of training opportunities for early-career researchers, including members of underrepresented groups, and methods for disseminating the results. Outcomes of the research will reveal how morphological development and natural selection have interacted over evolutionary history for this tribe of grasses and will provide agronomists with new insights for improving the productivity of its grain crops.

Researchers will test whether shifts in the integration and modularity of reproductive structures correlate with diversification in the Andropogoneae using three integrated aims that assess the phylogenetic, morphological, and functional consequences of these changes. They will produce a near-complete species-level phylogeny of Andropogoneae by leveraging extensive nuclear genome sequence data already in hand. Morphometric data for spikelets and spikelet pairs from all species will be captured using semi-automated tools and will be analyzed to assess the covariance between spikelet and spikelet pair structures (integration) and the morphometric distances between them (disparity and modularity). Integration, disparity, and modularity will then be mapped on the phylogeny, as will the underlying morphological characters, to be correlated with patterns of diversification. Experiments will test the performance of the spikelets and spikelet pairs for pollination and seed dispersal to quantify the functional consequences of integration and modularity. In doing so, researchers will augment herbarium collections with new metadata and contribute to genomic data repositories that will facilitate future research on grass systematic biology and plant breeding. The contributions of the research will create an integrated evolutionary view at the genomic level of morphological and functional diversification in a group of plants that are central to grassland ecology and US agriculture.

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.

National Science Foundation (NSF)
Division of Environmental Biology (DEB)
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Bruce Lieberman
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Donald Danforth Plant Science Center
St. Louis
United States
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