Rupert Barneby and his legume legacy
Scherson, Rosa , Choi, Hong-Kyu , Cook, Douglas R. , Sanderson, MJ .
Phylogenetics of New World Astragalus: the utility of genomics technology in reconstructing phylogenies at low taxonomic levels.
Astragalus is a very large group of flowering plants, comprising more than 2,500 annual and perennial herbaceous species that inhabit mostly cool, arid, continental regions of the Northern Hemisphere and South America. This genus was extensively studied by Rupert Barneby, whose decades of herbarium and field studies led to what is still today, the most comprehensive monograph of the genus in North America. The phylogeny of Astragalus has been difficult to reconstruct, because of low levels of sequence divergence. The New World species, inhabiting mountain areas of North and South America, are a clade nested within Old World Astragalus and exhibit even lower levels of variation. We relied on EST-based genome surveys of Medicago truncatula and other legume crop plants that had previously identified a suite of single copy nuclear genes in legumes. Ten primer pairs designed to span introns were subsequently screened by sequencing of PCR products or of clones, in 15 New World Astragalus species. Although these loci were single copy in Medicago, Astragalus species differ in ploidy levels and were expected to exhibit more complex genetics. Loci screened could be divided into those whose direct PCR sequencing yielded a clear product, and those in which subsequent cloning and sequencing showed the presence of multiple alleles or paralogs within Astragalus. Concatenation of several introns from independent loci or in some cases from multiple paralogs should lead to improved resolution of Astragalus phylogenetic relationships. This in turn will ultimately shed light on issues such as chromosome evolution, evolutionary correlates of plant rarity, and rates of speciation.
1 - University of California, Davis, Section of Evolution and Ecology, One Shields Ave., Davis, California, 95616, USA
2 - University of California, Davis, Plant Pathology, One Shileds Avenue, Davis, California, 95616, USA
Presentation Type: Symposium
Location: Magpie (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 2:45 PM