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

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.