A phylogenetic and morphological study of the Tectaria fuscipes group (Tectariaceae), with description of a new species

The fern species Tectaria fuscipes and morphologically similar species, which are common in tropical and subtropical mainland Asia, constitute a taxonomically confusing group. To better understand species boundaries and relationships within the T. fuscipes group, we conducted phylogenetic analyses of five plastid regions and morphological observations of herbarium specimens and living plants. As a result, we produced a generally well-resolved phylogeny of the T. fuscipes group and morphologically similar species in Asia. The phylogenetic analyses supported the T. fuscipes group including T. dissecta, T. fuscipes, T. ingens, T. paradoxa, T. setulosa, T. subfuscipes, T. subsageniacea and a new species, but excluding T. kusukusensis. However, T. fuscipes, T. subfuscipes and T. subsageniacea are almost indistinguishable in morphology, which form a complex characterized by the black linear-lanceolate stipe scales. The new species found in southern China and Vietnam is described here as T. fungii. It is similar to the T. fuscipes complex and T. kusukusensis, but differs from the former mainly by its brown-castaneous lanceolate stipe scales and from the latter by having nearly hairless laminae (versus frond axes abaxially bearing copious hairs).

分布于亚洲大陆热带、亚热带区域的棕柄三叉蕨（T. fuscipes）及其形态近缘物种，构成了一个分类学界定模糊的类群。为厘清该类群内的物种界限与系统演化关系，本研究对5个质体基因组区域开展了系统发育分析，并对馆藏标本及活体植株进行了形态学观察。研究结果显示，本研究成功构建了亚洲范围内棕柄三叉蕨类群及其近缘物种的高分辨率系统发育树。系统发育分析结果支持棕柄三叉蕨类群包含T. dissecta、T. fuscipes、T. ingens、T. paradoxa、T. setulosa、T. subfuscipes、T. subsageniacea以及1个新种，但不包含T. kusukusensis。然而，棕柄三叉蕨、亚棕柄三叉蕨与近萨根三叉蕨在形态上几乎无法区分，共同构成了以黑色线状披针形叶柄鳞片为典型特征的复合类群。本研究将发现于中国南部及越南的新种正式描述为T. fungii。该新种与棕柄三叉蕨复合群及恒春三叉蕨（T. kusukusensis）形态相近，与前者的主要区别在于其叶柄鳞片呈褐棕色披针形，与后者的差异则在于其叶轴几乎无毛，而恒春三叉蕨的叶轴背面密被大量柔毛。