蕨类植物的鳞片特征及演化I: 凤尾蕨科

鳞片是蕨类植物体表常见附属物, 是蕨类植物非常显著的分类学特征。凤尾蕨科(Pteridaceae)在蕨类植物系统发育中的位置关系多次发生了变化, 不同学者对该科中包含的类群也有着不同的观点。通过对该科76种植物的鳞片进行取材, 利用解剖镜观察拍照, 对各属鳞片特征进行描述。结果显示, 鳞片特征在不同的属和亚科之间具有明显的形态差异。用GenBank数据库中的rbcL基因序列对所研究物种进行系统发育重建, 并对鳞片的边缘特征和筛孔类型进行祖先性状重建, 结果表明, 全缘型鳞片和均质型鳞片是凤尾蕨科鳞片的祖征性状, 非全缘类型和透明筛孔类型的鳞片是在后期演化过程中形成的特征。此外, 透明和不透明类型的筛孔其形成可能与蕨类植物生活环境中的光照强度有关。

Morphology Characters and Evolution of Ferns Scale Ι: Pteridaceae

Scales are epidermal appendages on the rhizomes and leaves of many ferns. Features of scales play an important role in classification of ferns. The phylogenetic position and delimitation of Pteridaceae were treated differently by different authors. Here we collected scales of 76 fern species in Pteridaceae, and observed them under a dissecting microscope. By comparing the morphological characters, we found that scales are different among genus and subfamilies. We reconstructed a phylogenetic tree with the plastid rbcL sequence of the species in this study downloaded from GenBank database and reconstruced the ancestral state for two selected characters (margin of the scale and mesh type). The results suggested that homogeneous scale and entire margin were plesiomorphic characters, while non-entire margin and transparent mesh were evolved late in evolutionary process. We also speculated that the formation of transparent or non-transparent mesh may relate to the light intensity in the habitats.