XVI International Botanical Congess

After Riccia, Asterella is the largest genus of Marchantiales, estimated at 80 species worldwide. Species relationships are poorly understood and the existing infrageneric classification is based on a few arbitrary characters. Study of spore ornamentation and gametophytic and sporophytic characters such as sexual condition, pseudoperianth structure and sporogonium dehiscence has turned up neglected but potentially useful characters. Based on these a new classification of Asterella species is proposed. Molecular sequencing of two chloroplast genes trnL and matK is being used to test this classification. Assuming monophyly of Asterella, the major molecular clades accord well with groupings based primarily on spore characters. However, incorporation of molecular data from related genera calls the assumed monophyly of Asterella and other genera into question.