South African Journal of Botany 2004, 70(3): 393–406 Copyright © NISC Pty Ltd Printed in South Africa — All rights reserved SOUTH AFRICAN JOURNAL OF BOTANY ISSN 0254–6299 Circumscription of Apiaceae tribe Oenantheae TM Hardway1, K Spalik2, MF Watson3, DS Katz-Downie1 and SR Downie1* 1 Department of Plant Biology, University of Illinois, Urbana 61801, United States of America 2 Department of Plant Systematics and Geography, Warsaw University, Aleje Ujazdowskie 4, 00-478 Warsaw, Poland 3 Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, Scotland, United Kingdom * Corresponding author, email: [email protected] Received 18 August 2003, accepted in revised form 17 November 2003 Previous molecular systematic investigations into the Sium, and Trepocarpus. Relationships inferred from higher-level relationships of Apiaceae subfamily phylogenetic analyses of nuclear rDNA ITS sequences Apioideae have revealed a strongly supported clade from 64 accessions representing all 17 genera reveal recognised as tribe Oenantheae Dumort. These plants that four genera are not monophyletic. Bifora and may have clusters of fibrous or tuberous-thickened Cryptotaenia have members that fall outside of the tribe; roots, corky-thickened fruits, and other adaptations for Berula and Sium each comprise two or more lineages existence in wet or aquatic habitats. In some species, within Oenantheae. The St Helena endemics, Sium the leaves may be finely dissected or linear-septate and bracteatum and S. burchellii, ally with African Berula much reduced. We have initiated collaborative studies erecta; this clade is sister to the African endemic to produce a comprehensive estimate of phylogeny of species Sium repandum and Afrocarum imbricatum, the tribe, but such investigations are thwarted because and this entire group is allied closely with north tem- information on the composition of the tribe is lacking. perate Berula erecta. Nomenclatural changes are in Herein, tribe Oenantheae is circumscribed to include order, but must await further study. Representatives of the following genera: Afrocarum, Berula, Bifora (pro eight genera native to North America comprise a mono- parte), Cicuta, Cryptotaenia (pro parte), Cynosciadium, phyletic group, and results from relative rate tests sug- Daucosma, Helosciadium, Lilaeopsis, Limnosciadium, gest that this lineage is evolving much faster than any Neogoezia, Oenanthe, Oxypolis, Perideridia, Ptilimnium, other major clade recognised within the tribe. Introduction In all higher-level molecular systematic studies of Apiaceae although there are no characters that are common and subfamily Apioideae to date, whether based on chloroplast unique to the group. Its members are characterised general- DNA (cpDNA) restriction site comparisons or sequences ly by having fascicled roots (which may be thickened and from the nuclear ribosomal DNA internal transcribed spacer bear tubers) and glabrous leaves and stems. They are often (ITS) region or several chloroplast loci, the ‘Oenanthe clade’ associated with moist to wet habitats, and some are true is revealed as a strongly supported monophyletic group (e.g. aquatics. Many species, including the members of Berula, Plunkett et al. 1996, Downie et al. 1998, 2000b, Plunkett and Neogoezia, Perideridia, and Sium, have pinnate leaves with Downie 1999). A core group of genera is recognised in many primary divisions that are not further divided and are often of these studies, and includes Berula W.D.J. Koch, Cicuta rounded and of equal size, superficially resembling those L., Cryptotaenia DC., Helosciadium W.D.J. Koch, Oenanthe leaves of members of the distantly related genus Pimpinella L., Oxypolis Raf., Perideridia Rchb., and Sium L. The dis- L. Species inhabiting moist to wet habitats, including repre- tinctive genera Neogeozia Hemsl. and Lilaeopsis Greene, sentatives of Helosciadium, Sium, and Oenanthe, often whose affinities until recently were obscure, also belong have submerged leaves that are more finely dissected and within this clade (Plunkett et al. 1996, Petersen et al. 2002). have narrower lobes than those of the air-borne ones. The genera Cynosciadium DC., Limnosciadium Mathias and Leaves, particularly the petioles, are sometimes succulent Constance (1944–1945), and Ptilimnium Raf. may be includ- and the leaf lobes are reduced. In Berula, the lowest pair of ed as well, based on their similar vegetative and (or) fruit primary divisions is absent, whereas in Lilaeopsis and some morphologies (Downie et al. 2000b, 2001). Thirteen genera species of Oxypolis and Ptilimnium, all divisions are lacking have been recognised unequivocally as belonging to the and their initial number may only be inferred from the nodes Oenanthe clade. (septae) extant on the leaf axis. The fruits of many members The Oenanthe clade can be defined morphologically, are globose to broadly-ovate and are commonly 394 Hardway, Spalik, Watson, Katz-Downie and Downie spongy/corky thickened, facilitating dispersal in water Material and Methods (Affolter 1985, Wilm and Taft 1998). Indeed, Darwin (1859) was impressed by the lengthy flotation and subsequent ger- Taxonomic sampling mination abilities of Helosciadium. Lilaeopsis and Neogoezia have simple umbels, but this is an extremely rare To ascertain the limits of Apiaceae tribe Oenantheae, ITS feature of Apiaceae subfamily Apioideae. However, none of sequence data were procured from 100 accessions of sub- these attributes can be considered a synapomorphy for the family Apioideae using standard PCR and sequencing meth- clade, as each of these features can be found in genera out- ods (described below). These accessions included repre- side of the group (Petersen et al. 2002). This is not surpris- sentation of the 13 genera unambiguously placed in the tribe ing, given the fact that many tribes and clades recognised in as a result of earlier studies, plus Bifora americana (DC.) subfamily Apioideae on the basis of molecular data cannot Benth. & Hook., provisionally included in the tribe on the be delimited unambiguously using morphological or anatom- basis of matK sequence comparisons (Plunkett et al. 1996). ical data (Downie et al. 2001). These accessions also included representation of 19 addi- No prior taxonomic treatment has grouped together those tional genera (those listed in Table 1, plus Afrocarum, genera that are included here in the Oenanthe clade. In the Daucosma Engelm. & A. Gray ex A. Gray, and Trepocarpus system of classification of Pimenov and Leonov (1993), modi- Nutt. ex DC.) whose morphologies (or previous taxonomic fied from Drude (1898), the 13 genera recognised in the group placements, as indicated by their synonymies) suggested are distributed among three tribes (Apieae, Peucedaneae possible close affinities with those taxa already included in Dumort., and Smyrnieae Spreng.). Downie et al. (2000b) the tribe. recognised this group as tribe Oenantheae Dumort., but Sixty-four accessions were considered in the phylogenet- stressed that their circumscription of the tribe is radically differ- ic analysis (Table 2). The phylogenetic placement of the ent from that proposed by Dumortier (1827) and others, such African genus Afrocarum was ascertained by sampling puta- as Koso-Poljansky (1916) and Cerceau-Larrival (1962). tively allied genera Berula and Sium (Cannon 1978), from In this paper, we summarise the results of our efforts to Africa and elsewhere. Sampling of the genus Helosciadium identify additional members of Apiaceae tribe Oenantheae. was comprehensive (Wolff 1927, Z. Popper and M. Watson, We then report results of phylogenetic analyses of repre- unpubl. data). For Lilaeopsis and the seven exclusively sentatives of all genera comprising the tribe, placing empha- North American taxa (i.e. Bifora americana, Cynosciadium, sis on its African members, specifically the genera Berula, Daucosma, Limnosciadium, Neogeozia, Ptilimnium and Sium, and a new addition to the tribe, Afrocarum Rauschert. Trepocarpus), only single exemplars of each genus were Sequences of the ITS region were employed because they included, as their phylogenetic relationships are the subject have been shown to be appropriate to assess evolutionary of an ongoing, concurrent study (S. Downie et al., unpubl. relationships within Apiaceae subfamily Apioideae (Downie data). Sampling of the remaining genera (Cicuta, et al. 2001). Given that no previous classification has Cryptotaenia, Oenanthe, Oxypolis and Perideridia) was grouped together those genera here recognised as consti- based primarily on material availability. With the exception of tuting tribe Oenantheae, the results of this paper should Lilaeopsis, the nomenclatural type of each genus was facilitate further systematic activity on this widely distributed included in this study. and strongly supported monophyletic group of Apiaceae. Table 1: Taxa examined for inclusion in Apiaceae tribe Oenantheae but excluded on the basis of phylogenetic analysis of molecular data Genus Species examined (and synonyms) Chamaele Miq. C. decumbens (Thunb.) Makino (=Sium decumbens Thunb.; Oenanthe decumbens (Thunb.) Koso-Pol.) Crenosciadium Boiss. & Heldr. ex Boiss. C. siifolium Boiss. & Heldr. ex Boiss. Cyclospermum Lag. C. leptophyllum (Pers.) Sprague ex Britton & P. Wilson Huanaca Cav. H. andina Phil. Lichtensteinia Cham. & Schltdl. pro parte L. interrupta (Thunb.) Sond. (=Oenanthe interrupta Thunb.) Muretia Boiss. M. lutea (M. Bieb.) Boiss. (=Sium luteum (M. Bieb.) Spreng.) Naufraga Constance & Cannon N. balearica Constance