Phylogenomic Analysis of Astragalus

The legume Astragalus is the single most diverse genus of plants encompassing nearly 3,000 species. Not only is Astragalus remarkably diverse, but many species have considerable economic importance. For example, toxic Astragalus species also known as locoweed contain the chemical swainsonine which affects the reproductive and developmental traits of livestock and causes 100 million in annual losses in the United States alone. The genus is primarily distributed in temperate regions and is particularly diverse in southwest Asia (ca. 2,000 spp.), the Sino-Himalayas (ca. 400 spp.), western North America (ca. 400 spp.), and the Andes (ca.100 spp) The taxonomy and systematics of both Old World and New World Astragalus have been determined primarily through morphological analyses. Over the past 30 years, Astragalus has received considerable phylogenetics interest, which has yielded important results identifying the major groups, mainly in the Old World. However, due to the incredible species diversity and rapid diversification, previous efforts have been limited in their ability to resolve evolutionary relationships in this very large and complex clade. Previous studies have examined the relationships within Old World Astragalus but little is known about the major groups within the New World and the number of introductions from Asia. In this study, we sampled approximately 100 species from the extensive United States National Herbarium collection covering all sections of the New World to establish a phylogenetic framework for this poorly studied group. Using a novel technique called Hyb-Seq which combined hybrid enrichment with genome skimming, we were successful in obtaining both nuclear and chloroplast data to investigate the interesting relationships within Astragalus. We uncovered new migration events previously unknown, and elucidated on the complex relationships of this New World group.