Riccia cavernosa (Ricciaceae): a new addition to the liverwort flora of New Zealand

Abstract

ABSTRACTRiccia (Ricciaceae) is a widespread, cosmopolitan genus of thalloid liverworts. Here we document the presence of R. cavernosa Hoffm. in New Zealand for the first time. A full description based on New Zealand specimens is provided. Riccia cavernosa was discovered in New Zealand in February 2016 growing on the margins of a series of artificial wetlands constructed to aid in the recovery of a threatened endemic wading bird (Himantopus novaezelandiae). Following a review of the status of R. cavernosa in New Zealand we conclude that the species is most likely a recent natural, long distance trans-Tasman wind-dispersed arrival from Australia where the species is locally common. The discovery increases the number of Riccia reported from New Zealand from 10 to 11. Prior to the discovery of R. cavernosa, only four of the 10 Riccia recorded from New Zealand were considered indigenous. The conservation status of R. cavernosa is briefly discussed and a provisional assessment of ‘Threatened/Nationally Critical’ assigned to the species using the New Zealand Threat Classification System.