Expansion of the fern genus Lecanopteris to encompass some species previously included in Microsorum and Colysis (Polypodiaceae)

Abstract

The fern genus Microsorum is not monophyletic, with previous phylogenetic analyses finding three lineages to group not with the type species, but to form a grade related to the 13 species of Lecanopteris. These three lineages have recently been recognised as separate genera: Bosmania, Dendroconche, and Zealandia. Here, we explore the morphological characterisation of Lecanopteris and these other three lecanopteroid genera. While the traditional circumscription of Lecanopteris has seemed sacrosanct, its defining morphological character states of rhizome cavities and ant brooding associations occur in other lecanopteroid ferns and elsewhere in the Polypodiaceae. Instead, we suggest that the morphological characterisation of an expanded Lecanopteris including the Dendroconche and Zealandia lineages is just as good, if not better, with the pertinent character states being the absence of sclerenchyma strands in the rhizome and at least some fronds having Nooteboom’s type 5 venation pattern. This wider circumscription is also better able to accommodate phylogenetic uncertainty, and it means that groups of species traditionally placed together in a single genus are not distributed across different genera. General users familiar with the narrower circumscription of Lecanopteris will not be significantly disrupted, because there is little geographic overlap with the lineages added to the genus. Consequently, we make new combinations in Lecanopteris for 11 species and one subspecies.