On the differentiation and distribution of the rare New Zealand endemic Rehubryum bellii (Malta) F.Lara, Garilleti & Draper (Orthotrichaceae, Bryophyta)

ABSTRACT Introduction A recently published study revealed an unnoticed New Zealand endemic and monotypic genus, which was named Rehubryum. It was based on Ulota bellii, a species described by Nikolajs Malta for which only two previous collections were known. Despite this sample size limitation, Malta simultaneously published two varieties, each based on one of the two specimens: the type variety and U. bellii var. longicolla. Methods Specimens from 80 localities between 0 and 1430 m a.s.l. from both the North and South Islands of New Zealand were studied. Type material of both varieties of Ulota bellii was included in the study, and the ecological affinities of Rehubryum bellii were analysed. Key results and conclusions Morphometric analysis supports the conclusion that our recent collections correspond to the original concept of Ulota bellii, now combined as Rehubryum bellii. Additionally, var. longicolla is synonymised with the type variety based on a lack of morphological differences. Rehubryum bellii is described in detail and illustrated, and its distribution and ecological affinities are discussed. Rehubryum bellii presents a set of morphological diagnostic characters: leaves with a submarginal band of elongate cells, papillose-denticulate margins in the base–lamina transition, and an endostome with 16 segments. Similarities and differences between Rehubryum and Atlantichella, the sister genus from the northern hemisphere, as well as the distinction from Australasian species of Orthotrichaceae, are discussed. The genus is now known from 12 localities in montane areas of the South Island of New Zealand and two isolated mountains on the North Island.