Among the best-supported nodes in a cpDNA restriction site analysis by French et al. (1995) is a clade of Arisaema, Pinellia, Areae/Colocasieae, and Pistia. We investigated this clade using cpDNA sequences (trnL-F intron/spacer, rpl20-rps12 intron) to identify the sister group of Arisaema, the focus of a related project. Included were 30 species of Alocasia, Ariopsis, Arisaema, Arum, Biarum, Colocasia, Dracunculus, Eminium, Helicodiceros, Pinellia, Pistia, Protarum, Remusatia, Steudnera, Theriophonum, Typhonium (incl. Sauromatum) and Typhonodorum. Among many additional genera sampled was Lemna, based on previous suggestions that duckweeds might be close to Pistia. However, sequences of Lemna group with more basal aroids. The pantropical Pistia and the Seychelles endemic Protarum, both monotypic, are basal to the other 15 genera. They are followed by Ariopsis (Steudnera + Colocasia) from India, Burma, Indochina and Malesia, and Alocasia + Typhonodorum from Malesia and Madagascar, which are sister to a clade comprising the remaining genera. The latter split into Mediterranean-Himalayan Arinae (Arum, Biarum, Dracunculus, Eminium, Helicodiceros) + Remusatia and East Asian-North American Arisaema + Pinellia (Arisaema also extents into East Africa). Eocene leaves of Colocasieae and Oligocene seeds of Pistia constrain the minimal age of Arinae/Remusatia + Arisaema/Pinellia. The absence of significant rate heterogeneity in one of the three data sets permits time estimates for several evolutionary events, including Beringian crossing by the ancestors of North American Arisaema. Our poster also illustrates exceptional life form diversity: from free-floating aquatics (Pistia) to cold-wet adapted Arisaema to desert plants (Eminium spiculatum in the Negev; Arum, Biarum, and Eminium in semi-arid areas in central Asia and North Africa).

Key words: Araceae, Arisaema, biogeography, Lemnaceae, molecular clock, Pistia