Abstract Detail


SU, CHUN [1], Duan, Lei [2], Chang, Zhaoyang [3], Wen, Jun [4].

Chloroplast phylogenomics and character evolution of Eastern Asian Astragalus (Leguminosae) – tackling the phylogenetic structure of the largest genus of flowering plants in Asia.

Astragalus L. (locoweed) is an ecologically important plant genus and the largest genus of flowering plants (ca. 2900 species). It is morphologically diverse, evolutionarily relatively young, and taxonomically complicated. Previous studies suggested that many of the subgenera of Astragalus are not monophyletic and the phylogenetic relationships within the genus are still poorly known. We aimed to obtain a well-resolved phylogenetic framework for Astragalus, which is needed for further systematic and evolutionary work on this fascinating lineage of plants. For our study, we worked on the phylogenies of eastern Asian Astragalus, with emphasis on species from the Qinghai-Tibetan Plateau (QTP). QTP is a hotspot of plant biodiversity, and Astragalus species on the QTP have been poorly understood. To reconstruct the phylogenies of East Asian Astragalus and test its phylogenetic position, we sampled 117 taxa of Astragalus and its close relatives, covering 59 sections of the genus plus 30 outgroups to recover the main clades of East Asian Astragalus based on sequences of the whole chloroplast genome and 65 chloroplast CDSs via genome skimming. In our study, Astragalus is confirmed to be a monophyletic group which is a sister clade to the Oxytropis + Coluteoid clade, and yet most of the subgenera of Astragalus are supported to be not monophyletic.  Within Astragalus, we recovered ten clades, which differs from traditional Bunge’s subgeneric system. Also, we estimated the ancestral states of the trichome morphology and the habit via Bayesian Binary Method. Our study suggests that medifixed hairs developed at least five times and the annual habit developed at least six times. We dated the origin of Astragalus to the middle Miocene using BEAST, which is congruent with prior studies. In addition, previous geological studies have estimated the most recent stage active in the uplifting of the QTP to be around 2.6 Ma. We hypothesize that this uplifting, which led to aridification in East Asia and the adjacent regions, may have accelerated the rapid speciation of Astragalus, especially xerophilous groups (medifixed hair groups). According to our study, the divergence times of the medifixed hair groups ranged from 4.03 to 0.87 Ma, mostly 2-1 Ma, which are correlated with estimated phased QTP uplift. We found that the mesophytic groups, which are partly endemic to QTP, are the first and the second diverged clades of Astragalus s.strThese early diverged groups in the phylogeny support Barneby’s hypothesis about the most primitive group of Astragalus.

1 - Smithsonian Institution, 4115 8th St NW Washington DC, Washington, DC, 20011, United States
2 - South China Botanical Garden, Chinese Academy of Sciences, Xingke St. #723, Tianhe District, Guangzhou, Guangdong, 510650, China
3 - Northwest A&F University
4 - Botany, MRC-166 National Museum Of Natural History, 10th St. & Constitution Ave., NW, Mrc 166, Washington/DC, 20013, United States

Chloroplast Genome
East Asia

Presentation Type: Poster
Session: P, Phylogenomics Posters
Location: Virtual/Virtual
Date: Wednesday, July 29th, 2020
Time: 5:00 PM Time and date to be determined
Number: PPL005
Abstract ID:727
Candidate for Awards:None

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