Data from: Phylogenomics of Andropogoneae (Panicoideae: Poaceae) of mainland Southeast Asia

The grass tribe Andropogoneae is distributed in warm regions around the globe but has been poorly studied in mainland Southeast Asia. This is particularly true for the cosmopolitan genera Andropogon and Schizachyrium, with several species that appear to be narrowly distributed in this region. Additionally, lesser-known species in the genera Hemisorghum, Kerriochloa, and Pseudosorghum also occur in mainland Southeast Asia. A phylogeny is needed to address questions of taxonomy and trait evolution. Whole chloroplast genomes of Andropogoneae species and two outgroup species of Garnotia (tribe Arundinelleae) were analyzed using maximum likelihood (ML) and Bayesian inference (BI). Ancestral character states were reconstructed using ML for four morphological characters key to Andropogon and Schizachyrium identification. A previously-unidentified clade of Southeast Asian endemic taxa is found, including one species formerly classified in Andropogon. Other Southeast Asian taxa fall in an unresolved grade outside the major radiation of the tribe. Andropogon and Schizachyrium are both polyphyletic. Convergent evolution and reversal of characters are common throughout Andropogoneae. Addition of species from mainland Southeast Asian finds unexpected phylogenetic diversity. Southeast Asian Schizachyrium sanguineum forms two separate clades, which could reflect cryptic species differentiation, hybridization, introgression, or some combination.

须芒草族（Andropogoneae）广布于全球温暖地带，但针对中南半岛大陆地区的相关研究仍较为匮乏。这一现状在广布属须芒草属（Andropogon）与裂稃草属（Schizachyrium）上体现得尤为显著，该区域内多个该类群物种呈现狭域分布特征。此外，半高粱属（Hemisorghum）、凯氏草属（Kerriochloa）及伪高粱属（Pseudosorghum）中的鲜为人知物种也分布于中南半岛大陆区域。当前亟需开展系统发育研究，以解答该类群的分类学与性状演化相关问题。本研究对须芒草族物种的全叶绿体基因组，以及隶属于芦竹族（Arundinelleae）的格尼草属（Garnotia）的2个外类群物种进行了分析，分析方法采用最大似然法（maximum likelihood, ML）与贝叶斯推断法（Bayesian inference, BI）。本研究针对须芒草属与裂稃草属物种鉴定的4个关键形态性状，采用最大似然法重建了其祖先性状状态。研究发现了一个此前未被识别的东南亚特有类群分支，其中包含1个曾被归类于须芒草属的物种。其余东南亚类群则处于该族主要辐射演化支系之外的一个未明确界定的级阶。须芒草属与裂稃草属均为多系类群。性状的趋同演化与逆转在须芒草族中普遍存在。纳入中南半岛大陆地区的物种后，研究发现了意料之外的系统发育多样性。东南亚的红裂稃草（Schizachyrium sanguineum）形成了两个独立的分支，这一现象可能反映了隐存物种分化、杂交、基因渐渗，或是这些过程的组合。