Phylogenetic investigation of Asparagus L. trait evolution, phylogeography and diversification

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Garden asparagus is one of more than two hundred species within the plant genus Asparagus. Wild Asparagus species range from the southern tip of South Africa, throughout Europe to the eastern reaches of Asia, and exhibit remarkable variation in growth forms and modes of reproduction. Whereas garden asparagus is a non-woody species with fleshy roots, many other species produce woody stems as bushes or persistent vines, and still other species produce potato-like tuberous root. The familiar garden asparagus has separate pollen-producing male and fruit-bearing female plants, whereas most of its relatives are hermaphroditic - meaning the flower has both male and female parts combined. Previous hypotheses suggest that this high level of diversity is the result of adaptation to geographic spread due to changing environmental conditions. The objective of this research is to determine when, where and under what environmental conditions this diversity of growth and reproduction strategies arose within Asparagus. The researchers will use genomic methods to resolve the phylogenetic relationships among all described Asparagus species and then determine how changes in growth form and mode of reproduction correlate with environmental changes and biogeographic spread. The findings will allow generalizations for modeling how plants may adapt to changing environments in the future. This, in turn, will be significant to cultivation and production of domestic Asparagus. For example, the results will provide asparagus breeders information to help develop new varieties that can thrive in the face of increasing droughts in Southern California or fungal pathogens in the moist environments of the Midwest and Northeastern U.S.State-of-the-art genomic, phenotyping and modeling approaches will be utilized to develop a robust, comprehensive phylogeny for the genus Asparagus, and to elucidate its dynamic biogeographic history and adaptations to varied environmental conditions. Garden asparagus (A. officinalis) is already a model for the evolution of dioecy. This project will expand our understanding of the evolution of trait diversity in Asparagus to include storage root form, shoot architecture and deciduousness, the development of photosynthetic stems in place of leaves, and the transformation of leaves into reduced, non-photosynthetic scales and thorns with diverse forms and functions. Integrating species-level phylogenomics, environmental data, and phenomics, we will test for interactions among the genetic, ecological and evolutionary processes that have been driving diversification within Asparagus over the last 5-10 million years. Novel methods of image analysis that have been developed for intraspecific high-throughput phenotyping will be expanded to model macroevolutionary changes in shoot and root architecture. These developments will propel new lines of research on both within species and interspecific biodiversity.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.