Systematic Botany (2000), 25(4): pp. 668±691 q Copyright 2000 by the American Society of Plant Taxonomists Phylogenetic Relationships in the Commelinaceae: I. A Cladistic Analysis of Morphological Data TIMOTHY M. EVANS1 Department of Botany, University of Wisconsin, 430 Lincoln Drive, Madison, Wisconsin 53706 1Present address, author for correspondence: Department of Biology, Hope College, 35 East 12th Street, Holland, Michigan 49423-9000 ROBERT B. FADEN Department of Botany, NHB 166, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560 MICHAEL G. SIMPSON Department of Biology, San Diego State University, San Diego, California 92182 KENNETH J. SYTSMA Department of Botany, University of Wisconsin, 430 Lincoln Drive, Madison, Wisconsin 53706 Communicating Editor: Richard Jensen ABSTRACT. The plant family Commelinaceae displays a wide range of variation in vegetative, ¯oral, and in¯orescence morphology. This high degree of variation, particularly among characters operating under strong and similar selective pressures (i.e., ¯owers), has made the assessment of homology among morpho- logical characters dif®cult, and has resulted in several discordant classi®cation schemes for the family. Phy- logenetic relationships among 40 of the 41 genera in the family were evaluated using cladistic analyses of morphological data. The resulting phylogeny shows some similarity to the most recent classi®cation, but with some notable differences. Cartonema (subfamily Cartonematoideae) was placed basal to the rest of the family. Triceratella (subfamily Cartonematoideae), however, was placed among genera within tribe Tradescantieae of subfamily Commelinoideae. Likewise, the circumscriptions of tribes Commelineae and Tradescantieae were in disagreement with the most recent classi®cation. The discordance between the phylogeny and the most recent classi®cation is attributed to a high degree of convergence in various morphological characters, par- ticularly those relating to the androecium and the in¯orescence. Anatomical characters (i.e., stomatal struc- ture), on the other hand, show promise for resolving phylogenetic relationships within the Commelinaceae, based upon their agreement with the most recent classi®cation. The Commelinaceae, a well de®ned family of 41 neae is found mainly in Africa and Asia. Only six genera and about 650 species, is characterized by genera (Aneilema, Buforrestia, Commelina, Floscopa, several features including a distinct closed leaf Murdannia, and Pollia) have indigenous species in sheath, a succulent leaf blade, and three-merous both hemispheres. ¯owers with distinct petals and sepals (Cronquist Older classi®cations of the Commelinaceae relied 1981; Faden 1985; Faden and Hunt 1991). The gen- heavily on ¯oral features (see Faden and Hunt 1991, era are largely tropical and subtropical, but several for a review). Woodson (1942) ®rst used in¯ores- extend into temperate regions. The greatest diver- cence characters for higher-level classi®cation, but sity is in Africa, where, along with Madagascar, he was largely unfamiliar with the Old World gen- nearly half the genera and about 40% of the species era. Pichon (1946) employed anatomical characters are found (Faden 1983a). to separate the genus Cartonema as the family Car- There is a natural division of taxa between the tonemataceae, but he returned to more traditional Old and the New World. The seven subtribes of characters to de®ne his ten tribes of Commelina- tribe Tradescantieae (sensu Faden and Hunt 1991) ceae. Brenan (1966) used a variety of morphological are each wholly con®ned to either the Eastern or characters to de®ne 15 informal ``groups'' of gen- Western hemisphere, whereas the tribe Commeli- era. These have served as the basis of surveys of 668 2000] EVANS ET AL.: COMMELINACEAE 669 anatomical (Tomlinson 1966, 1969) and cytological molecular and morphological studies are similar to (Jones and Jopling 1972) characters in the family, the molecular phylogenies (e.g., Chase et al. 1995; but they have little taxonomic signi®cance. Linder and Kellogg 1995). Recent work by Givnish, The most recent classi®cation, which will be used Evans, Pires, and Sytsma (Givnish et al. 1995, 1999) in this study, was put forward by Faden and Hunt generally supports these ®ndings. It also places the (1991). In their classi®cation, the Commelinaceae is Hanguanaceae as the sister family of the Comme- divided into two unequal subfamilies (Table 1). linaceae and the Xyridaceae and Eriocaulaceae in Subfamily Cartonematoideae contains the tribes the grass/sedge clade. Cartonemateae and Triceratelleae, each comprising Certain morphological characters also lend sup- a single genus. Subfamily Commelinoideae con- port to the separation of the Commelinaceae from tains the remaining 38 genera that are arranged in other families of the original Commelinales (sensu two tribes, Tradescantieae and Commelineae, the Cronquist 1981, or Dahlgren et al. 1985). As dis- former of which is divided into seven subtribes. cussed above, Dahlgren et al. (1985) separated the Evans (1995) conducted a cladistic analysis of the Commelinaceae from the other commelinoid fami- Commelinaceae using both morphological and mo- lies in part by the presence of raphides, which are lecular characters. This paper represents a modi®- absent in the Mayacaceae, Rapateaceae, Xyridaceae, cation and expansion of the morphological com- and Eriocaulaceae (Dahlgren and Clifford 1982). ponents of that study. Raphides are widespread, however, in the Ponted- Relationships of Commelinaceae to other Mono- eriaceae, Philydraceae, and Haemodoraceae (Dahl- cot Families. The family Commelinaceae is the gren et al. 1985). Additionally, whereas the Com- namesake for the order Commelinales. Cronquist melinaceae were separated from other families in (1981) de®ned the order by the presence of perfect the Commelinales by the presence of an amoeboid ¯owers that are adapted for general insect polli- tapetum, the genus Pontederia and all investigated nation, having showy petals that are differentiated members of the Haemodoraceae also have an amoe- from the sepals. He included three other families in boid tapetum (Dahlgren and Clifford 1982; Simp- this order: Xyridaceae, Rapateaceae, and Mayaca- son 1988, 1990). Finally, ¯owers in the Commeli- ceae. He separated the Commelinaceae from the naceae show a strong tendency toward zygomor- other three families by their well-de®ned and phy, whereas they are generally actinomorphic in closed leaf sheath, and the succulent blade. the other members of the Commelinales sensu Dahlgren et al. (1985) included the same families Cronquist (1981) or Dahlgren et al. (1985). Zygo- in Commelinales as Cronquist, but with the addi- morphic ¯owers are common, however, in the Pon- tion of the Eriocaulaceae. Eriocaulaceae was placed tederiaceae, Philydraceae, and Haemodoraceae. in its own order by Cronquist, who maintained that Although numerous taxonomic treatments have it was most likely derived within Xyridaceae. Dahl- been produced for the Commelinaceae, there has gren et al. (1985) distinguished the Commelinaceae been little consensus as to which characters should from the other commelinoid families by the pres- be used to de®ne relationships among the genera. ence of raphides, an amoeboid tapetum, and the The earlier systems relied heavily upon features of leaf characters used by Cronquist (closed leaf the highly variable androecium, but they ignored sheath and succulent blade). characters of the in¯orescence. The classi®cation Although cladistic analyses of morphological produced by Faden and Hunt (1991), which will be data support a monophyletic Commelinales sensu used throughout this study, incorporated a broad Dahlgren et al. (1985; Stevenson and Loconte 1995), range of information, such as characters from mor- recently published molecular data suggest other- phology, anatomy, and palynology. None of these wise. Nucleotide sequence data from the chloroplast classi®cations, however, is rooted in an evolutionary gene rbcL (Chase et al. 1993; Clark et al. 1993; Du- framework. The purpose of this study was to ex- vall et al. 1993) place the Commelinaceae near the amine the intergeneric relationships in the Com- Pontederiaceae, Philydraceae, and Haemodoraceae, melinaceae using morphological and anatomical all of which are part of a larger clade containing characters in a cladistic analysis. the families of the order Zingiberales. The Rapatea- ceae (the only other representative of Commelinales MATERIALS AND METHODS included in the previous molecular studies) is placed in a different clade that contains, among Operational Taxonomic Units (OTU's). A criti- other families, Poaceae and Cyperaceae. Combined cal step in any cladistic analysis is the selection of 670 SYSTEMATIC BOTANY [Volume 25 TABLE 1. Classi®cation of the Commelinaceae (as presented by Faden and Hunt 1991). *indicates Old World subtribe, **indicates New World subtribe. Family: Commelinaceae R. Br. Subfamily: Cartonematoideae (Pichon) Faden & D. Hunt Tribe: Cartonemateae (Pichon) Faden & D. Hunt Cartonema R. Brown Tribe: Triceratelleae Faden & D. Hunt Triceratella Brenan Subfamily: Commelinoideae (BruÈ ckner) Faden & D. Hunt Tribe: Tradescantieae (Meisner) Faden & D. Hunt Subtribe: *Palisotinae Faden & D. Hunt Palisota Reichb. Subtribe: *Streptoliriinae Faden & D. Hunt Streptolirion Edgew. Spatholirion Ridley Aetheolirion Forman Subtribe: *Cyanotinae (Pichon) Faden & D. Hunt Cyanotis D. Don (Including Amischophacelus R. Rao & Kamm.)