Notes on Menisciopsis wailele (Thelypteridaceae), a Critically Endangered Rheophytic Fern Species from Kaua‘i, Hawaiian Islands

Abstract. Menisciopsis wailele (Thelypteridaceae) is a single-island endemic fern species restricted to the Hawaiian island of Kaua‘i. All observations indicate it is an obligate rheophyte, preferring sites of fast-moving water along concave walls of remote streams and waterfall edges. This paper presents data on its morphology, evolution, taxonomy, distribution, abundance, and ecological characteristics. Based on phylogenetic and geographic evidence, the ancestor of the Hawaiian species of Menisciopsis may have dispersed from the mountains of continental East Asia. A formal IUCN assessment of the species has been completed and is reported here as Critically Endangered (CR B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)).