Gymnogrammitis dareiformis is a polygrammoid fern (Polypodiaceae) — Resolving an apparent conflict between morphological and molecular data

Maximum parsimony and maximum likelihood analyses of the combined data sets of two chloroplast genes, rbcL and rps4, demonstrate that the monotypic genus Gymnogrammitis is part of the polygrammoid clade (Polypodiaceae + Grammitidaceae), and not the Davalliaceae as proposed in most studies. The genus forms a clade together with two Asiatic genera of the Polypodiaceae, Arthromeris and Selliguea. These last two genera have either simple or once-pinnate leaves, whereas Gymnogrammitis has highly divided (3- to 4-pinnate) blades. Two characters of this genus, the basic chromosome number of x = 36 and the absence of indusia, support a relationship with the Polypodiaceae. Neither feature is found within Davalliaceae. Three morphological characters support the placement of Gymnogrammitis within the selligueoid lineage of Polypodiaceae: spores with a thick perine extending in microspines, sclerenchymatous strands in the rhizome, and non-clathrate rhizome scales. These results demonstrate that molecular and morphological data are phylogenetically congruent with the exception of blade dissection. Our study clearly shows the pitfalls of classifications based on single characters, and illustrates the importance of phylogenetic assessment of all taxonomic conclusions.