Translator Disclaimer
1 April 2006 New Insights into the Phylogeny of the Genus Hymenophyllum s.l. (Hymenophyllaceae): Revealing the Polyphyly of Mecodium
Sabine Hennequin, Atsushi Ebihara, Motomi Ito, Kunio Iwatsuki, Jean-Yves Dubuisson
Author Affiliations +
Abstract

With more than 100 species, Mecodium is the largest infrageneric taxon of Hymenophyllum s.l. It was long considered a natural and homogeneous group, but recent phylogenetic studies have questioned this assertion. Using rbcL, rbcL-accD, and rps4-trnS sequences, we demonstrate that Mecodium is highly polyphyletic. Several species of Mecodium form the derived clade “H. polyanthos”; one species is nested within a second derived clade; and the remaining species are assigned to five basal clades including taxa regarded as distantly related. These clades are strongly supported both by parsimony and Bayesian analyses, but the relative placement of the basalmost clades lacks support. We show that the members of “basal Mecodium” are characterized by features that are plesiomorphic for Hymenophyllum s.l.—a reduced or dorsi-ventral stele, a lamina generally at least partially thickened, and a chromosome number based on x = 36, whereas taxa in the “H. polyanthos” clade have a subcollateral stele, the one-cell thick lamina typical of the family, and x = 28. There is a high level of variation among the basal species, and, notably, the rhizome indumentum is shown to be an interesting character for distinguishing among the basal clades. These new findings stress the need for further studies on Hymenophyllum s.l., and reassessment of its classification.

Sabine Hennequin, Atsushi Ebihara, Motomi Ito, Kunio Iwatsuki, and Jean-Yves Dubuisson "New Insights into the Phylogeny of the Genus Hymenophyllum s.l. (Hymenophyllaceae): Revealing the Polyphyly of Mecodium," Systematic Botany 31(2), 271-284, (1 April 2006). https://doi.org/10.1600/036364406777585775
Published: 1 April 2006
JOURNAL ARTICLE
14 PAGES


Share
SHARE
RIGHTS & PERMISSIONS
Get copyright permission
Back to Top