Data from: Morphological, phylogenetic, and ecological diversity of the new model species Setaria viridis (Poaceae: Paniceae) and its close relatives

Premise of the study: Species limits of the emerging model organism Setaria viridis (tribe Paniceae, subtribe Cenchrinae) are not well defined. It is thought to be related to S. adhaerens, S. faberi, S. verticillata, and S. verticilliformis and in North America occurs with the morphologically similar S. pumila. An integrated approach was taken to evaluate its variation and relationships with the other taxa. Methods: Statistical morphology, flow cytometry, molecular phylogenetics, and growth experiments were employed to examine the group’s physical variation, polyploidy, evolutionary relationships, and drought ecology, respectively. Key results: Setaria viridis contributed one genome to the tetraploids S. faberi, S. verticillata, and S. verticilliformis; the other genome of the latter two was contributed by S. adhaerens. Setaria pumila is unrelated. Morphologically, S. viridis is most similar to S. faberi, but all tested accessions of S. viridis were diploid, whereas those of S. faberi were all tetraploid. Principal component analysis of 70 morphological characters consistently separated S. viridis from S. faberi, largely by spikelet characters. The diagnostic morphological characters are not affected by watering. Setaria faberi is far more sensitive to drought, in terms of mortality and morphological stunting, than S. viridis or S. pumila. Conclusions: Setaria viridis is a diploid species and has contributed to several polyploid derivatives. The most morphologically similar of the polyploids is S. faberi, which differs in spikelet features, phylogenetics, genome size, and ecological response to drought. Researchers using field-collected S. viridis as a model organism will benefit from the clear delimitation provided in this study.

研究背景：新兴模式生物狗尾草（Setaria viridis，隶属于黍族（Paniceae）、蒺藜草亚族（Cenchrinae））的物种界定仍不明确。一般认为其与S. adhaerens、S. faberi、S. verticillata及S. verticilliformis近缘，在北美地区与形态相似的S. pumila伴生。本研究采用整合研究策略，对其变异特征及与其他类群的亲缘关系展开评估。
研究方法：本研究分别运用统计形态学、流式细胞术、分子系统发育学及生长实验，依次探究该类群的形态变异、多倍体特性、进化亲缘关系与干旱生态学特征。
主要结果：狗尾草为四倍体物种S. faberi、S. verticillata及S. verticilliformis贡献了一套基因组；后两个类群的另一套基因组均由S. adhaerens提供。S. pumila与狗尾草无亲缘关系。形态学上，狗尾草与S. faberi最为相似，但所有被测的狗尾草居群均为二倍体，而S. faberi的所有被测居群均为四倍体。对70个形态性状的主成分分析结果一致显示，狗尾草与S. faberi可被清晰区分，该区分主要基于小穗性状。诊断性形态性状不受浇水条件影响。相较于狗尾草或S. pumila，S. faberi在死亡率及形态矮化方面对干旱胁迫的敏感性显著更高。
结论：狗尾草为二倍体物种，并为多个多倍体衍生类群贡献了基因组。多倍体类群中与狗尾草形态最相似的是S. faberi，二者在小穗特征、系统发育关系、基因组大小及干旱生态响应方面均存在显著差异。本研究明确了狗尾草的物种界定，将为以野外采集的狗尾草作为模式生物开展研究的学者提供重要参考。