BS 54 85 A cladistic analysis of morphological features in Bidens L. and Coreopsis L. (Asteraceae-Heliantheae) with notes on generic delimitation and systematics Mesfin Tadesse, Daniee J. Crawford & Seung-Chul. Kim Mesfin Tadesse, Crawford, D.J. & Seung-Chul Kim. 2001. A cladistic analysis of morphological features in Bidens L. and Coreopsis L. (Asteraceae-Heliantheae) with notes on generic delimita­ tion and systematics. Biol. Skr. 54: 85-102. ISSN 0366-3612. ISBN 87-7876-246-4. A cladistic analysis of morphological characters obtained from representative species of Bidens from North, Central & South America and Africa, and Coreopsis from North and South America indicate that: (a) Bidens and Coreopsis are not monophyletic; (b) Bidens is a paraphyletic genus and is closer to Cosmos, Thelesperma, Heterosperma, Isostigma, etc., than it is to Coreopsis-, (c) the African species that were formerly kept in Coreopsis form a paraphyletic grade within Bidens that are sister to western hemisphere groups; (d) Coreopsis is paraphyletic with two major clades and is restricted to the New World; and (e) the phylogeny based on morphology shows certain similar­ ities to one generated from DNA sequences, but the relationships portrayed differ in several basic respects. Mesfin Tadesse, Ohio State University, Department of Evolution, Ecology and Organismal Biology, Colum­ bus, Ohio 43210-1293, USA (permanent address Addis Ababa University, Department of biology, National Herbarium, P.O. Box 3434, Addis Ababa, Ethiopia}. E-mail: tadesse. [email protected] Daniel J. Crawford, University of Kansas, Department of Ecology and Evolutionary Biology, Lawrence, Kansas 66045-2106, USA. E-mail: [email protected] Seung-Chul Kim, formerly: Indiana University, Department of Biology, Bloomington. Now: University of California at Riverside, Department of Botany and Plant Sciences, Riverside, Califonia 92521-0124, USA. E-mail: [email protected] Introduction Benth. (Smith 1975, 1989; Melchert & Turner Bidens L. and Coreopsis L. belong to the tribe 1990; Karis & Ryding 1994). Recently the sys­ Heliantheae, subtribe Coreopsidinae of Aster- tematic position of Bidens within the Coreop­ aceae. In a systematic review of the tribe, the sidinae has been the focus of studies by Ryding Coreopsidinae was subdivided into seven in­ & Bremer (1992) and by Karis & Ryding formal groups (Stuessy 1977). Bidens L. and Core­ (1994). The latter stated that Bzdcnsand Coreop­ opsis L., along with other genera, were put in sis offer one of “the most striking examples of group 1. A number of authors also place Bidens difficulties with generic delimitation” in the near Coreopsis, Cosmos Cav. and Coreocavpus Asteraceae. 86 BS 54 In a cladistic analysis of the Coreopsidinae winged achenes in Coreopsis (Sherff 1936), (given as tribe Coreopsideae), Ryding & Bre­ without considering other features, has mer (1992: 653) recognized three large blurred the boundary between this genus and generic groups, although their strict consensus Bidens. Smith & Parker (1971) showed that the tree does not resolve relationships among the presence or absence of wings on achenes of groups. An analysis of 18 of the same genera Coreopsis tinctoria L. is under simple genetic (four genera have been relegated to synonymy, control. Similar problems exist with delimiting cf. Bremer 1994; Veldkamp & Kreffer 1991), Coreocarpus from Bidens and Coreopsis (Smith with fuller data sets than hitherto, also pro­ 1983b, 1984b, 1989; Melchert & Turner 1990). duced an unresolved strict consensus tree. Most North American (excluding Mexico) Shannon & Wagner (1997) pointed out that species of Bidens are annual plants and are dis­ the conclusions of Ryding & Bremer (1992) tinct from Coreopsis both in capitular and gross “... concerning relationships within the Core­ morphology. The Mexican species, however, opsideae should be viewed with some intergrade particularly with Cosmos and Coreo­ caution ...” Much data are missing from their carpus (Melchert 1990b). The only true species matrix (e.g. 23 of 37 characters are unknown of Coreopsis in the eastern hemisphere are the for Cyathomone S.F. Blake, and approximately a lew cultivated and/or ornamental species: C. third of the characters for Bidens and Coreopsis grandiflora Hogg, C. verticillata L. and C. lanceo- are recorded as variable). lata L. One reason given for the unresolved posi­ The paucity of features distinguishing Bidens tion of Bidens in the cladograms generated by from Coreopsis, the instability of the characters Rycling & Bremer ( 1992) was lack of diagnostic traditionally used for segregating the two gen­ characters between it and Coreopsis. The tradi­ era, and the large amount of phenotypic plas­ tional delimitation of these genera, which, as ticity of particularly Bidens as exemplified by shown elsewhere as inadequate (c.g. Wild 1967; studies on amphibious taxa (Wheedon 1974) Agnew 1974; Mesfin Tadesse 1984, 1986), are and those of oceanic islands, have obscured adopted in their work. A number of studies, the boundary between Coreopsis and Bidens. particularly on Cosmos (Melchert 1967, 1968, There are morphological similarities 1990a), Dahlia Cav. (Sorensen 1969; Giannasi between some species of Bidens and Coreopsis. 1972, 1975a, 1975b), Co reopsis (many articles by However, there are also capitular and foliar Crawford & Smith), Bidens (Hart 1979; Ballard resemblances between some species of Bidens 1986; Ganders & Nagata 1983, 1984; Mesfin and other related genera, i.e. Cosmos, Coreocar­ Tadesse 1984, 1986, 1993; Helenurm & Gan­ pus, Isostigma Less., etc. In order to determine ders 1985; Mesfin Tadesse et al. 1995a, 1995b, the relationships between particularly Bidens 1996; Roseman 1986), Coreocarpus (Smith 1989; and Coreopsis, a cladistic analysis of genera of Melchert & Turner 1990), and Thelesperma the Coreopsidinae incorporating data from Less. (Melchert 1963), have indicated that previous (Ryding & Bremer 1992; Mesfin prior circumscriptions of genera are in need of Tadesse et al. 1995a, 1995b) and current stu­ modification in light of newly emerging data. dies is attempted here. Melchert (1975) reiterated that the main The objectives of the present work are a) to reason that Bidens and Cosmos “appear to inter­ determine the phylogenetic positions of Bidens grade is due to the a priori inclusion of all an­ and Coreopsis within the Coreopsidinae, b) to nuals with beaked or rostrate achenes within test the monophyly of Bidens and Coreopsis, and Cosmos. Similarly, the inclusion of all taxa with also evaluate the characters that have been BS 54 87 used traditionally for generic segregation, c) to to be paraphyletic (Rieseberg & Brouillet provide a cladistic analysis of the relationships 1994). between Bidens and Coreopsis, (including those The first run on the entire data matrix (18 African species which have previously been genera, 28 characters) produced an unre­ kept in Coreopsis), and d) to provide an assess­ solved consensus tree (tree not shown). Sub­ ment of the utility of certain characters used sequently, a few of the heterogeneous genera for sectional classification in Bidens. (Chrysanthellum, Coreocarpus, and Fitchia llook.f.) and those, which assumed many dif­ ferent positions (Chrysanlhellum, Coreocarpus, Materials and methods Moonia Arn. and Henricksonia B.L. Turner) on Taxa the cladograms, were excluded from the ana­ For the initial cladistic analysis of subtribe lysis, except for Coreocarpus. This dicl not Coreopsidinae, sensu Ryding & Bremer adversely affect the topology. The result is pre­ (1992), a total of 15 genera and 28 characters sented in Fig. 1. were included (Appendix 1 and Table 1). From As shown in Fig. 1, Bidens is closely related to the twenty-five genera included in the subtribe several other genera, i.e. Thelesperma Fess., Cos­ by Ryding & Bremer (1992), four (z.c. Eryngio- mos, Megalodonta, Heterosperma Gav., Narvalina phyllum Greenm. (= Chrysanthellum Rich.), Glos- Cass., Trioncinia, and Coreocarpus. Coreopsis is sis­ sogyne Cass., Guerreroia Merr., and Neuractis ter to the clade containing the above men­ Cass. (= Glossocardia Cass.; cfr. Veldkamp & Kref- tioned taxa, as well as Dahlia Cav. and Isostigma. fer 1991; Bremer 1994) have since then been Therefore, in the subsequent cladistic analysis relegated to synonymy. Of the remaining 21 of Bidens and Coreopsis, a representative from genera, Cyathomone S.F. Blake, Dicranocarpus A. each of the Dahlia-Isostigma clade, Cosmos-Mega- Gray, Goldmanella Greenm., Ericentrodea S.F. lodonta-Thelesperma clade, and Heterosperma-Nar- Blake & Sherff and Petrolnum R.Br. are valina-Trioncinia-Coreocarpus clade was also excluded from the analysis due to lack of com­ included. A total of 32 species and 45 charac­ plete data or specimens. Megalodonta Greene ters (Appendix 2 and Table 2) were used. Sev­ (Roberts 1985; Bremer 1994), which was con­ eral representatives of Coreopsis from North sidered by Sherff (1937) as a monotypic sec­ America (6 spp.) and Mexico & South America tion of Bidens and was embedded in Bidens in (3 spp.), were included. In the case of Bidens, the ITS phylogeny by Kim et al. (1999)), was several members from Africa (10 spp.), North included in the present analysis. Trioncinia (F. America excluding Mexico (5 spp.), and South Muell.) Veldkamp (a monotypic North Aus­ America & Mexico (5 spp.), were also included tralian genus ‘distinguished from Bidens only in the analysis. by its alternate leaves’) was likewise included in the present analysis. Characters Genera rather than