2000 Volume 89 Pages 55-70
Five Hypopterygium species, H. tamarisci, H. laricinum, H. tenellum, H. muelleri, and H. debile, exhibit remarkable morphological similarities and form a species complex (H. tamarisci complex).
This study unravels the problematic delimitation of the species in this complex using molecular (cpDNA trnLUAA intron) and morphological data. Sequences of the trnLUAA intron of taxa belonging to the H. tamarisci complex are remarkably similar. In a maximum parsimony tree, the taxa form a polytomous clade within one well-supported clade of other Hypopterygium species (H. filiculaeforme and H. didictyon). The Hypopterygium clade is well-separated from both the outgroup species, Lopidium concinnum, and from the clade of Canalohypopterygium tamariscinum and Catharomnion ciliatum. Morphological research showed, that the “taxa” of the H. tamarisci complex can not be sharply delimited from one another, but they can be delimited from the other Hypopterygium species as a single, variable and widely distributed species: H. tamarisci. Hypopterygium debile, H. laricinum, H. muelleri, and H. tenellum are shown to be synonymous with H. tamarisci.
