A reassessment of the little-known Amazonian fern Diplazium praestans based on molecular and morphological evidence

Family- and genus-level circumscription of ferns in the suborder
Aspleniineae (eupolypods II) has long been controversial, due in part to
confusion about the relationship among the families Aspleniaceae and
Athyriaceae.  Recent studies have demonstrated that character
states traditionally used to infer a close relationship between these two
families are either symplesiomorphic or homoplastic, and re-examination of
numerous taxa has led to the recircumscription of several clades, and the
description of several new families and genera.  In light of
these findings, we re-evaluated the taxonomic affinities of Diplazium
praestans, a little-known fern from western Amazonia that is
morphologically disparate to the remainder of Neotropical Diplazium.
 Using sequence data from three chloroplast markers and analysis
of eight morphological characters, we demonstrate that Diplazium praestans
was erroneously placed in that genus and instead is a Hymenasplenium.
 We place it in a phylogenetic context, reassess its morphology
in light of our findings, evaluate its conservation status under IUCN
criteria, and provide a new combination: Hymenasplenium praestans.
 We also provide an updated key to the Neotropical species of
Hymenasplenium and discuss unresolved taxonomic problems in the genus.