Circumscription of Apiaceae tribe Oenantheae

• Published in: South African journal of botany Vol. 70; no. 3; pp. 393 - 406
• Main Authors: Hardway, T.M., Spalik, K., Watson, M.F., Katz-Downie, D.S., Downie, S.R., van Wyk, B.-E., Tilney, P.M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2004
• ISSN: 0254-6299; 1727-9321
• DOI: 10.1016/S0254-6299(15)30222-2

Previous molecular systematic investigations into the higher-level relationships of Apiaceae subfamily Apioideae have revealed a strongly supported clade recognised as tribe Oenantheae Dumort. These plants may have clusters of fibrous or tuberous-thickened roots, corky-thickened fruits, and other adaptations for existence in wet or aquatic habitats. In some species, the leaves may be finely dissected or linear-septate and much reduced. We have initiated collaborative studies to produce a comprehensive estimate of phylogeny of the tribe, but such investigations are thwarted because information on the composition of the tribe is lacking. Herein, tribe Oenantheae is circumscribed to include the following genera: Afrocarum, Berula, Bifora (pro parte), Cicuta, Cryptotaenia (pro parte), Cynosciadium, Daucosma, Helosciadium, Lilaeopsis, Limnosciadium, Neogoezia, Oenanthe, Oxypolis, Perideridia, Ptilimnium, Sium and Trepocarpus. Relationships inferred from phylogenetic analyses of nuclear rDNA ITS sequences from 64 accessions representing all 17 genera reveal that four genera are not monophyletic. Bifora and Cryptotaenia have members that fall outside of the tribe; Berula and Sium each comprise two or more lineages within Oenantheae. The St Helena endemics, Sium bracteatum and S. burchellii, ally with African Berula erecta; this clade is sister to the African endemic species Sium repandum and Afrocarum imbricatum, and this entire group is allied closely with north temperate Berula erecta. Nomenclatural changes are in order, but must await further study. Representatives of eight genera native to North America comprise a monophyletic group, and results from relative rate tests suggest that this lineage is evolving much faster than any other major clade recognised within the tribe.