Riccia L. (Ricciaceae): Current Australian research on a remarkable complex thalloid liverwort genus.

D. Christine Cargill

Riccia L. is the most biodiverse genus within the complex thalloid liverworts. It is found on all continents except Antarctica and from the tropics to the Arctic Circle. Greatest species richness occurs in Mediterranean–type environments and species of Riccia have developed many different strategies to survive in dry habitats. Understanding the role of this group of liverworts in the Australian environment, particularly in Biological Soil Crusts (BSC) requires knowledge of which species occupy this continent. Recent taxonomic research on Australian Riccia, has resulted in numerous taxa being sequenced for the first time, the majority from the monsoon tropics of the Northern Territory. This has allowed for testing of a number of infrageneric and several morphological species concepts. Molecular data from three chloroplast and one nuclear marker support the genus as monophyletic, however, the monophyly of the two largest subgenera, Riccia and Ricciella A. Braun is not supported, with the latter nested deep within subg. Riccia. A second tree reconstruction using only trnL-F sequences allowed the inclusion of extra-Australian material. Results from this study indicated congruence between material of some Australian and extra-Australian taxa, with further research required to determine the taxonomic placement of remaining taxa. A number of widespread and common species were also found to be polyphyletic. One such species, R. inflexa, was investigated further resulting in the recognition of two species in Australia.

Presenting Author:  D. Christine Cargill

Author Affiliation: Australian National Herbarium, Centre for Australian National Biodiversity Research