毛叶粉背蕨配子体的泌粉现象及其系统学意义

Farina Observation in Gametophytes of Aleuritopteris squamosa (Pteridaceae), with Comments on Its Phylogenetic Significance

摘要:

为探讨蕨类配子体泌粉现象的系统学意义,对5 种粉背蕨属(Aleuritopteris)植物的配子体发育过程进行了观察。结果表明,毛叶粉背蕨(A. squamosa)的配子体(通常是雌配子体)也具有泌粉现象,而其他4 种的配子体不具粉状分泌物。基于叶绿体rbcL 序列的证据表明,毛叶粉背蕨与粉背蕨属其他植物、中国蕨属(Sinopteris)等构成一个具有强烈支持率的单系,即Hemionitids 支,该支与美洲分布的隐囊蕨类互为姐妹群。因此,配子体泌粉现象在碎米蕨类中并非隐囊蕨类植物所特有,泌粉现象的产生,在系统发育上至少涉及2 次独立的演化事件。毛叶粉背蕨的泌粉现象多发生在雌性配子体上,暗示配子体的泌粉可能与配子体的雌性分化和胚发生发育相关。

Abstract:

In order to understand the phylogenetic significance of farina in gametophytes of fern, the gametophyte development of five Aleuritopteris species were observed. The results showed that the gametophytes (usually female gametophytes) of A. squamosa had also farina phenomena. Based on the evidence of chloroplast rbcL sequences, it was confirmed that A. squamosa is a member of the Hemionitids, one of four well-supported clades resolved by molecular data. The American Notholaena, within which the farinose gametophytes were formerly reported, was resolved as monophyletic, forming a sister group to the Hemionitids. As the farinose gametophyte now observed in two of the four clades of cheilanthoid ferns (Heminitids and Notholaenids), it was postulated that the farinose gametophyte would be derived independently at least twice in the evolution of the cheilanthoid ferns. The fact that the farina is produced exclusively in female gametophytes implies that the occurring of the farina would be relevant to the gender differentiation and the embryo formation in cheilanthoid ferns.