Identifying a mysterious aquatic fern gametophyte
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Süßwassertang, a popular aquatic plant that is sold worldwide in aquarium markets, has been long considered a liverwort because of its ribbon-like thallus. However, its antheridia are remarkably fern-like in morphology. To corroborate the hypothesis that Süßwassertang is a fern gametophyte and to determine its closest relative, we have sequenced five chloroplast regions (rbcL, accD, rps4–trnS, trnL intron, and trnL-F intergenic spacer), applying a DNA-based identification approach. The BLAST results on all regions revealed that Süßwassertang is a polypod fern (order: Polypodiales) with strong affinities to the Lomariopsidaceae. Our phylogenetic analyses further showed that Süßwassertang is nested within the hemi-epiphytic fern genus Lomariopsis (Lomariopsidaceae) and aligned very close to L. lineata. Our study brings new insights on the unexpected biology of Lomariopsis gametophytes—the capacity of retaining a prolonged gametophytic stage under water. It is of great interest to discover that a fern usually known to grow on trees also has gametophytes that thrive in water.
KeywordsAquarium DNA barcoding DNA-based identification Gametophyte Fern Lomariopsis Lomariopsidaceae
The authors thank Li-Yaung Kuo for laboratory help, Tien-Chuan Hsu for collecting Taiwanese Lomariopsis spectabilis, and Dr. Wen-Liang Chiou (Taiwan Forestry Research Institute) for valuable comments.
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