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.

圆叶沟繁缕（Elatine rotundifolia）于2008年在厄瓜多尔被发表为新物种，其鉴定依据为独特的形态特征与地理分布范围。然而，我们在最初检视该物种的模式标本时发现，尽管该类群与沟繁缕属（Elatine）存在部分表面相似性，但其分类归属存在误判。我们借助形态学与分子数据对这一归属疑点展开了研究。研究发现，圆叶沟繁缕（Elatine rotundifolia）在若干营养器官与繁殖器官的特征上均与沟繁缕属（Elatine）其他类群存在显著差异，这表明其系统亲缘关系实则与母草科（Linderniaceae，唇形亚纲；菊亚纲）更为接近，而非沟繁缕科（Elatinaceae，蔷薇亚纲；超蔷薇类）。随后，我们针对内转录间隔区（internal transcribed spacer, ITS）的DNA序列开展了系统发育分析，分析样本涵盖圆叶沟繁缕（Elatine rotundifolia）的等模式标本，以及沟繁缕科、母草科与其他被子植物支系的多个代表类群。分子数据显示，圆叶沟繁缕（Elatine rotundifolia）嵌入微繁缕属（Micranthemum，母草科）的多个采集样本分支中，其系统发育位置与田繁缕属（Bergia）及沟繁缕属（Elatine，沟繁缕科）的样本相距甚远。基于上述结果，我们得出结论：圆叶沟繁缕（Elatine rotundifolia）所指代的类群实为沟繁缕属的误置类群，实则应为母草科微繁缕属（Micranthemum）成员，且可能与水生物种微繁缕（M. umbrosum）为同物异名。