用核DNA和叶绿体DNA序列鉴别铁线蕨属<italic>Adiantum</italic> L. (凤尾蕨科)新的隐性杂交种

Abstract

Natural hybridization has been commonly found in ferns and is generally believed to happen independently at different locations if the range of the parent species overlaps. In 2013, we collected seven species of Adiantum from Yuanjiang, Yunnan, China. The identity of one of these collections remained in doubt; the plant is very similar to A. meishanianum ( A. malesianum × A. philippense ), a natural hybrid from Taiwan, China. Morphological comparison showed that this unidentified collection was different from other related taxa. Sequencing of a single copy of an exon ( CRY2 exon 3) of the nuclear genome suggested this plant contained haplotype sequences of both A. sinicum and A. menglianense. Therefore, it should be treated as a new hybrid. Phylogenic analysis based on five chloroplast DNA sequences ( rbc L, atp B, atp A, trn L-F and rps 4- trn S) indicated that the plant was clustered in A. sinicum, which could be considered to be the female parent of the hybrid. This new hybrid is not only similar to A. meishanianum in morphology, but also its parental taxa are in sister groups in the phylogeny. Hence, the new hybrid was considered to be a cryptic hybrid species. Our methods could be extended to identify other potential natural fern hybrids in China. The habit of clonal propagation potentially occurs in nature, so this natural hybrid could easily survive in the field because clonal growth can offset the lack of fitness caused by sexual reproductive isolation, which may be an important reason why so many hybrid ferns exist in nature.