Data from: Evidence for the transfer of Elatine rotundifolia to Linderniaceae

Elatine rotundifolia was described in 2008 from Ecuador as a new species because of its unique morphology and geographical distribution. However, an examination of type material for E. rotundifolia suggested to us initially that this taxon had been assigned incorrectly to Elatine, despite some superficial similarity to that genus. This possibility was investigated using morphological and molecular data. We found that E. rotundifolia differed from other members of Elatine by several vegetative and reproductive features, which indicated a distant alliance closer to Linderniaceae (Lamiids; Asterids) rather than Elatinaceae (Fabids; Superrosids). We then conducted a phylogenetic analysis of DNA sequences from the internal transcribed spacer region, which included isotype material of E. rotundifolia, as well as various representatives of Elatinaceae, Linderniaceae, and other angiosperm clades. The molecular data resolved E. rotundifolia among several accessions of Micranthemum (Linderniaceae) in a position quite remote phylogenetically from accessions of Bergia and Elatine (Elatinaceae). From these results, we conclude that the name E. rotundifolia refers to a taxon that was misplaced in Elatine, and represents instead a member of Micranthemum (Linderniaceae), and possibly is synonymous with the aquatic species M. umbrosum.2008年，研究人员基于厄瓜多尔的标本将圆叶沟繁缕（Elatine rotundifolia）发表为新物种，因其具备独特的形态学特征与地理分布格局。然而，我们在最初检视该物种的模式标本时发现，尽管圆叶沟繁缕与沟繁缕属（Elatine）存在一定表面相似性，但该分类群被错误归入沟繁缕属。我们遂采用形态学与分子生物学数据对这一可能性展开验证。研究发现，圆叶沟繁缕在多项营养与繁殖特征上均与沟繁缕属其他类群存在显著差异，这表明其系统亲缘关系与沟繁缕科（Elatinaceae；Fabids；Superrosids）较远，而与母草科（Linderniaceae；Lamiids；Asterids）更为接近。随后，我们针对内转录间隔区（internal transcribed spacer）的DNA序列开展系统发育分析，分析样本涵盖圆叶沟繁缕的等模式标本、沟繁缕科、母草科的多个代表类群，以及其他被子植物演化支。分子数据显示，圆叶沟繁缕与母草科薄柱草属（Micranthemum）的多个采集标本聚为一支，其系统发育位置与沟繁缕科节节菜属（Bergia）和沟繁缕属（Elatine）的采集标本相距较远。基于上述结果，我们得出结论：圆叶沟繁缕的学名原本被错误归入沟繁缕属，实则应为母草科薄柱草属（Micranthemum）的类群，且极有可能与水生物种M. umbrosum为同物异名。