Abstract Detail

Systematics

Charboneau, Joseph [1], Cronn, Rich [2], Liston, Aaron [3], Wojciechowski, Martin [4], Sanderson, Michael [1].

Examining the evolution of selenium hyperaccumulation in the New World clade of Astragalus (Fabaceae) using phylogenomics.

A large clade of about 450 milkvetch species (Astragalus L., Fabaceae) in the Americas called Neo-Astragalus is thought to have arisen through a rapid radiation only within the last about 4.5 million years. Neo-Astragalus is particularly diverse in western North America, and many species have become specialists on different geologic substrates. Among the edaphic specialists in the clade are about two dozen species of selenium hyperaccumulators that are confined to selenium-rich soils and greatly concentrate the element in their tissues, which makes them highly toxic to most herbivores. Although the monophyly of Neo-Astragalus itself has been well supported, phylogenetic relationships within the clade (including among selenium hyperaccumulators) have remained elusive because of low levels of sequence variation in the small number of genes sequenced thus far. To improve the resolution of relationships within Neo-Astragalus, we used genome skimming data to assemble whole plastomes and the entire nuclear ribosomal DNA (nrDNA) cistron from 94 Astragalus species representing 55 of 85 described Neo-Astragalus sections. Both the plastome and nrDNA phylogenies begin to resolve recalcitrant backbone relationships within the clade, and we compare topologies and branch support in both trees. We also identified at least three different large-scale inversions in plastomes and evaluate their utility as phylogenetic characters. Using ancestral state reconstruction, we examine the evolution of selenium hyperaccumulation to estimate the number of origins and losses of the trait and the relationships among different kinds of edaphic specialists.

1 - University Of Arizona, Department Of Ecology And Evolutionary Biology, 1041 E. Lowell St., Tucson, AZ, 85721, United States
2 - USDA Forest Service, Pacific Northwest Research Station, 3200 SW Jefferson Way, Corvallis, OR, 97330, United States
3 - Oregon State University, Department Of Botany & Plant Pathology, 2082 Cordley Hall, Corvallis, OR, 97331, United States
4 - Arizona State University, School Of Life Sciences, PO Box 874501, Tempe, AZ, 85287, United States

Keywords:
phylogenomics
genome skimming
Chloroplast Genome
plastome
nuclear ribosomal DNA
Fabaceae
Leguminosae
Astragalus
edaphic specialization.

Presentation Type: Oral Paper
Session: SYS3, Systematics III: Cooley Award presentations
Location: Virtual/Virtual
Date: Wednesday, July 29th, 2020
Time: 11:30 AM
Number: SYS3007
Abstract ID:844
Candidate for Awards:George R. Cooley Award