Riccardia dimorpha sp. nov. (Hepaticophyta, Aneuraceae) from Western Nelson, New Zealand, exhibiting sexually determined morphological dimorphism, an overlooked feature of some liverworts

Riccardia dimorpha is described from 24 collections made in New Zealand between 1984 and 2020 from Western Nelson, Westland, and Fiordland ecological provinces in the South Island, and from Stewart Island / Rakiura. These specimens were misidentified as R. browniae [ R. pusilla (Steph.) E.A.Br., nom. illeg.], R. asperulata R.M.Schust., R. multicorpora E.A.Br., and R. perspicua E.A.Br. , or identified only to genus. Riccardia dimorpha belongs to the Riccardia section Alcicornia H & auml;ssel and is characterised by having strong striations on the epidermis, a subterete thallus, a monopodial growth form, endomycorrhizae absent from the ventral epidermis, and epidermal cells are the same size as internal cells. Specimens were collected in fireinduced Leptospermum scoparium shrublands, on peat soils at lowland to montane elevations. Riccardia dimorpha is sexually dimorphic in plant size and number of branches (meristematic tip number), and male and female plants differ to the degree that the sexuality of a plant can be determined without finding sexual branches on a plant. Such dimorphism is rarely reported in liverworts although is common in mosses.