Classification of Convolvulaceae: a Phylogenetic Approach

Systematic Botany (2003), 28(4): pp. 791±806 q Copyright 2003 by the American Society of Plant Taxonomists Classi®cation of Convolvulaceae: A Phylogenetic Approach SASÏA STEFANOVICÂ ,1,3 DANIEL F. A USTIN,2 and RICHARD G. OLMSTEAD1 1Department of Botany, University of Washington, Box 355325, Seattle, Washington 98195-5325; 2Conservation and Science Department, Sonora Desert Museum, 2021 N Kinney Road, Tucson, Arizona 85743; 3Author for correspondence, present address: Department of Biology, Indiana University, 1001 E. Third Street, Bloomington, Indiana, 47405 ([email protected]) Communicating Editor: Paul S. Manos ABSTRACT. Because recent molecular studies, based on multiple data sets from all three plant genomes, have indicated mutually congruent, well-resolved, and well-supported relationships within Convolvulaceae (the morning-glory family), a formal reclassi®cation of this family is presented here. Convolvulaceae, a large family of worldwide distribution, exhibiting a rich diversity of morphological characteristics and ecological habitats, are now circumscribed within twelve tribes. A key to these tribes of Convolvulaceae is offered. The group of spiny-pollen bearing Convolvulaceae (forming ``Echinoconiae'') and tribe Cuscuteae are retained essentially in their traditional sense, Cresseae are circumscribed with only minor modi®- cations, Convolvuleae and Erycibeae are recognized in a restricted sense, while Dichondreae and Maripeae are expanded. Also, to produce a tribal taxonomy that better re¯ects phylogenetic relationships, the concept of Poraneae is abandoned as arti®cial, three new tribes are recognized (Aniseieae, Cardiochlamyeae, and Jacquemontieae), and a new tribal status is proposed for the Malagasy endemic Humbertia (Humbertieae). ``Merremieae'' are tentatively retained even though the mono- phyly of this tribe is not certain. In addition to the formal classi®cation, we provide clade name de®nitions for the family as well as for most of the clades recognized presently as tribes. Also, ®ve well-supported clades that are not assigned formal ranks are recognized and their names de®ned. The reevaluation of traditional taxonomic characters reveals that many hom- oplasious characters were emphasized in previous classi®cations, resulting in formal recognition of non-monophyletic groups. Putative morphological synapomorphies for many clades discovered through molecular cladistic analyses are discussed. However, the morphology of several clades that are well-supported by DNA evidence remains poorly understood, creating further challenges for future studies in Convolvulaceae. Recent advances in understanding of the phyloge- ®cation were subsequently adopted by many authors netic relationships within Convolvulaceae, the morn- (but see Roberty 1952, 1964), with modi®cations con- ing-glory family, based on molecular data sets drawn cerning mainly the taxonomic ranks. from all three plant genomes, indicate the need for a The most comprehensive traditional work at the revised classi®cation of this family (Manos et al. 2001; family level was offered by Austin (1973) based mainly Miller et al. 2002; Stefanovic et al. 2002; Stefanovic and on chromosome numbers. Austin's treatment (1973, Olmstead in press). modi®ed 1998) is currently the most widely used tra- The morning-glory family comprises approximately ditional classi®cation. Following Austin, the nonpara- 1600±1700 species grouped in 55±60 genera (Mabber- sitic members of the family are circumscribed in nine ley 1987). The family is nearly cosmopolitan in distri- tribes (Table 1). Cuscuta, the only parasitic taxon asso- bution, but its members are primarily tropical plants, ciated with Convolvulaceae, is treated as a separate with many genera endemic to tropical zones of indi- monotypic family, Cuscutaceae. vidual continents (Austin 1998). Uncertainties exist re- The major traditional synoptic works on ¯owering garding both delimitation of the family and intrafa- plants place Convolvulaceae in the order Solanales milial (tribal) circumscription. Currently available clas- (sensibus Cronquist 1988; Dahlgren 1989; Thorne 1992) si®cations within Convolvulaceae rely largely on the along with the Polemoniaceae, Hydrophyllaceae, and work of several earlier workers, including Choisy Solanaceae. Takhtajan (1997) placed this family in its (1845), Bentham and Hooker (1873), Hallier (1893), Pe- own order, Convolvulales, due to a number of char- ter (1891, 1897), and Roberty (1952, 1964). An overview acteristics, such as presence of articulated latex canals of these, including both points of con¯ict and congru- and latex cells, intraxylary phloem position, distinct ence among them, is presented by Austin (1973; his seed structure and pollen morphology, not shared with Table 8). All of these pre-cladistic schemes are based other Solanales. Results of broad molecular phyloge- on very few characters considered to be ``the most im- netic studies of angiosperms in general, and Asteridae portant'' by the author. Among the most in¯uential are in particular, based on limited molecular data for the those of Peter (1891), based upon fruit type, and Hal- Convolvulaceae suggested that the family is most lier (1893), adopted by Peter (1897), based on pollen closely related to the Solanaceae and Montiniaceae surface features as well as fruit and stylar characters. (e.g., Olmstead and Palmer 1992; Olmstead et al. 1992, Hallier divided the family into two groups: ``Echino- 1993, 2000; Chase et al. 1993; Soltis et al. 1997, 2000; coniae'', with spiny pollen surface, and ``Psiloconiae'', APG 1998; Savolainen et al. 2000). with smooth pollen. The major outlines of this classi- Some members of Convolvulaceae, especially Cus- 791 792 SYSTEMATIC BOTANY [Volume 28 TABLE 1. Synopsis of Convolvulaceae classi®cationÐa compar- TABLE 1. Continued. ison of the most recent traditional (Austin 1973, 1998) and newly proposed phylogenetic classi®cation. Asterisks (*) indicate genera Austin (1973, Phylogenetic classi®cation modi®ed 1998) (present study) not sampled in any molecular study of Convolvulaceae (see text), Family Family but retained in present classi®cation in their putative respective Tribe Tribe tribes based on morphology. Pound signs (#) indicate genera Genus Genus found not to be monophyletic as circumscribed traditionally. Quo- Poraneae Porana p.p. tation marks (`` '') indicate the tribe not con®rmed to be mono- Porana Metaporana phyletic (see text). Metaporana Calycobolus# Calycobolus Dipteropeltis Austin (1973, Phylogenetic classi®cation Dipteropeltis Rapona modi®ed 1998) (present study) Family Family Rapona Erycibeae Tribe Tribe Cordisepalum Erycibe Genus Genus Poranopsis Cardiochlamyeae Convolvulaceae Convolvulaceae Cardiochlamys Cordisepalum Argyreieae Ipomoeeae s.l. Tridynamia Poranopsis Argyreia Argyreia Dinetus Cardiochlamys Blinkworthia (including Rivea) Tridynamia Rivea Astripomoea Cuscutaceae Porana p.p. Ipomoeeae Blinkworthia* Cuscuteae Dinetus Ipomoea Ipomoea# Cuscuta Humbertieae Astripomoea Lepistemon Humbertia Lepistemon Lepistemonopsis* Lepistemonopsis Paralepistemon Paralepistemon Stictocardia Stictocardia Turbina# cuta and Ipomoea, have been used as model systems to Turbina ``Merremieae'' address a wide variety of biological questions. Many # Merremieae Merremia species of the parasitic genus Cuscuta are recognized Merremia Hewittia Hewittia Hyalocystis* as pests on a large array of important agricultural Decalobanthus Decalobanthus* crops. A substantial body of literature deals with the Operculina Xenostegia life history, ecology, and pest control of Cuscuta species Xenostegia Operculina (reviewed by Dawson et al. 1994, and references there- Hyalocystis Convolvuleae Aniseia Convolvulus in). These branch parasites are also frequently used to Iseia (including Calystegia) study haustorial initiation and formation (e.g., DoÈrr Odonellia Polymeria 1987; Heide-Jùrgensen 1987; Lee and Lee 1989; Sub- Tetralocularia Aniseieae ramaniam and Mahadevan 1994). In addition, Cuscuta Convolvuleae Aniseia has been the subject of extensive molecular analyses. Calystegia (including Iseia) Convolvulus Odonellia The diversity of photosynthetic ability among species Polymeria Tetralocularia prompted several physiological studies of photosyn- Jacquemontia Cuscuteae thetic enzymes and molecular evolution studies of the Erycibeae Cuscuta chloroplast genome (Machado and Zetsche 1990; Ha- Maripa Jacquemontieae Dicranostyles Jacquemontia berhausen et al. 1992; Haberhausen and Zetsche 1994; Lysiostyles Maripeae BoÈmmer et al. 1993; Freyer et al. 1995). Species attri- Erycibe Dicranostyles buted to the genus Ipomoea are exceptionally morpho- Humbertia Maripa logically diverse, varying in habit and vegetative and Hildebrandtieae Lysiostyles* reproductive morphology. Due to this diversity Ipo- Hildebrandtia Cresseae s.l. Sabaudiella Hildebrandtia moea species have been the focus of a broad range of Cladostigma (including Cladostigma evolutionary and molecular genetic studies including Cresseae and Sabaudiella) maintenance of ¯oral polymorphisms, mating system Seddera Seddera evolution, and evolution of ¯avonoid biosynthetic path- Evolvulus Evolvulus Cressa Cressa way (reviewed by Miller et al. 1999). Bonamia Bonamia# Convolvulaceae have been the subject of only two Stylisma Stylisma family-wide molecular phylogenetic studies (Stefan- Wilsonia Wilsonia ovic et al. 2002; Stefanovic and Olmstead in press). The Itzaea Itzaea ®rst study (Stefanovic et al. 2002) was based on se- Neuropeltis Neuropeltis Neuropeltopsis

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