FloraOfNewZealand-Mosses-26-Fife-2016-Rhizogoni ...

The Rhizogoniaceae are a moderately large family distributed mainly in tropical regions and subtropical to cool parts of the southern hemisphere and are well represented in New Zealand by members of five genera. Species of the core genus, Rhizogonium, are particularly attractive and often conspicuous terrestrial or epiphytic plants. Their leaves are inserted in two ranks and the shoots flattened; three species of this genus are widespread in N.Z. Our one species of Cryptopodium, an endemic genus often growing on tree-ferns, is one of the largest mosses in our flora. The less conspicuous but highly attractive Goniobryum exhibits a classic disjunction between N.Z., eastern Australia (including Tasmania) and the southern tip of South America. The circumscription of the family and of some of its genera, especially Rhizogonium in its broadest sense, has been in a state of flux for decades. For example, the genus Pyrrhobryum, represented by three species in N.Z., has been segregated from the traditionally defined Rhizogonium. Further “splitting” of Pyrrhobryum, has been proposed by some workers, but is rejected here. The Rhizogoniaceae and allied families are considered to occupy a critical evolutionary position relative to pleurocarpous mosses, and they have recently attracted considerable attention from molecular systematists. Some but not all of the taxonomic changes derived from the molecular studies have been accepted here. The enigmatic and gymnostomous genus Calomnion, a conspicuous occupant of N.Z. tree fern caudices, is here accepted as a member of the family. Many studies, by contrast, retain Calomnion in its own family, with historically controversial affinities. Calomnion is represented in N.Z. by a single species, with segregate described species rejected here. Two other small but ecologically important genera in N.Z. (Leptotheca and Hymenodon), sometimes placed here, have been excluded from the family in part because of published molecular studies.