Systematic Botany (2007), 32(3): pp. 660–670 # Copyright 2007 by the American Society of Plant Taxonomists Taxonomic Revisions in the Polyphyletic Genus Tabebuia s. l. (Bignoniaceae) SUSAN O. GROSE1 and R. G. OLMSTEAD Department of Biology, University of Washington, Box 355325, Seattle, Washington 98195 U.S.A. 1Author for correspondence ([email protected]) Communicating Editor: James F. Smith ABSTRACT. Recent molecular studies have shown Tabebuia to be polyphyletic, thus necessitating taxonomic revision. These revisions are made here by resurrecting two genera to contain segregate clades of Tabebuia. Roseodendron Miranda consists of the two species with spathaceous calices of similar texture to the corolla. Handroanthus Mattos comprises the principally yellow flowered species with an indumentum of hairs covering the leaves and calyx. The species of Handroanthus are also characterized by having extremely dense wood containing copious quantities of lapachol. Tabebuia is restricted to those species with white to red or rarely yellow flowers and having an indumentum of stalked or sessile lepidote scales. The following new combinations are published: Handroanthus arianeae (A. H. Gentry) S. Grose, H. billbergii (Bur. & K. Schum). S. Grose subsp. billbergii, H. billbergii subsp. ampla (A. H. Gentry) S. Grose, H. botelhensis (A. H. Gentry) S. Grose, H. bureavii (Sandwith) S. Grose, H. catarinensis (A. H. Gentry) S. Grose, H. chrysanthus (Jacq.) S. Grose subsp. chrysanthus, H. chrysanthus subsp. meridionalis (A. H. Gentry) S. Grose, H. chrysanthus subsp. pluvicolus (A. H. Gentry) S. Grose, H. coralibe (Standl.) S. Grose, H. cristatus (A. H. Gentry) S. Grose, H. guayacan (Seemann) S. Grose, H. incanus (A. H. Gentry) S. Grose, H. lapacho (K. Schum.) S. Grose, H. pulcherrimus (Sandwith) S. Grose, H. pumilus (A. H. Gentry) S. Grose, H. riodocensis (A. H. Gentry) S. Grose, H. selachidentatus (A. H. Gentry) S. Grose, H. serratifolius (Vahl) S. Grose, H. spongiosus (Rizzini) S. Grose, H. subtilis (Sprague & Sandwith) S. Grose and H. uleanus (Kraenzl.) S. Grose. KEYWORDS: Handroanthus, Roseodendron, Tabebuia, taxonomy. Tabebuia, as currently circumscribed with 100 delimitation of Tabebuia has continued into recent species, is the largest genus in Bignoniaceae and is times (Mattos 1970; Gentry 1972). distributed from the southwestern U.S. to northern Mattos (1970) divided Tabebuia into two different Argentina and Chile. Over the course of its groups, indicating that a group of Brazilian taxa taxonomic history, it has been split and re- known as ‘‘iˆpes’’ should not remain in Tabebuia. assembled several times, as researchers interpreted His reasoning appears to have been based on the the morphological diversity in different ways. The original concept for Tabebuia, which he defined as wide range of morphological diversity suggests having simple leaves and an ovary that in cross there may be more than one lineage included section has 3–4 ovules/locule. This morphology is within the traditional concept of Tabebuia. Recent consistent with the type of Tabebuia, T. cassinoides, studies (Spangler and Olmstead 1999; Grose and but is the most exclusive concept for Tabebuia since Olmstead 2007) have confirmed that Tabebuia,as it was proposed by de Candolle (1838). Neither did currently delimited, is polyphyletic. Therefore, the Mattos think theˆ ipes belonged in Tecoma, due to generic boundaries need to be redefined in their palmately compound leaves. He created the Tabebuia and related genera. The goal of this paper genus Handroanthus for those species with pal- is to revise the generic classification to be consis- mately compound leaves and 8–9 series of ovules/ tent with its phylogeny. locule, and typified this genus with Handroanthus The name Tabebuia has a long and convoluted albus (Tabebuia alba). history (Gentry 1969). This name was first published Gentry (1972, 1992) included Handroanthus in by de Candolle (Candolle 1838) who applied it to Tabebuia, insisting that Tabebuia as previously de- bignoniaceous trees with ‘‘simple’’ leaves. Howev- lineated is natural. Gentry (1972) was adamant that er, the concept of Tabebuia came to be expanded to the large genus Tabebuia should not be broken up encompass a large amount of morphological di- further, and expressed his ‘‘sincere hope that future versity. As researchers examined and monographed students of Bignoniaceae will consider the case of this taxon, a number of concepts of Tabebuia Handroanthus before succumbing to further parox- emerged, producing a labyrinthine synomomy ysms of unwarranted splitting’’ (Gentry 1972). (Candolle 1838; Raffinsque 1838; Sprague and Gentry (1992) recognized some groups within Sandwith 1932). In addition, there was confusion Tabebuia, however. In his treatment for Flora as to the boundaries between Tecoma and Tabebuia Neotropica he defined 10 species groups although (Miers 1863; Seeman 1863; Bureau 1864; Schumann he placed two species, T. arimaoensis and T. 1894; Rheder 1913). Much of the confusion between heterophylla, in both groups 9 and 10. The largest Tecoma and Tabebuia was sorted out by Britton of Gentry’s groups are primarily species endemic (Britton 1915). However, disagreement as to the to the Greater Antilles (55 species). He did not use 660 2007] GROSE & OLMSTEAD: REVISION OF TABEBUIA 661 phylogenetic terminology to describe the relation- (Fig. 1C, F). The lepidote scales in a group of ships, but he clearly believed that this group of species (such as Tabebuia pilosa) may be stalked. Anillean species was monophyletic and sister to The wood anatomy of Tabebuia group I is distinc- a group of mainland species that are spread tive; it is lightweight, with medium specific gravity throughout the continental part of the genus’ range of 0.4–0.74, and lacks lapachol (dos Santos and (Gentry 1992). Miller 1992). The heartwood is indistinct from the Tabebuia donnell-smithii was placed in Tabebuia by sapwood and the rays are 1–2 cells in width (dos Rose (1892) with some reservation: ‘‘The species, Santos and Miller 1992). This group has leaves are while not agreeing in all respects with Tabebuia, ‘simple’ (or unifoliolate) or 3–7(9)-merous, depend- answers better to this than to any other known ing on species (Gentry 1992). The fruits are linear- genus. In its inflorescence and ribbed pods it is cylindrical and smooth on the surface (Gentry more like Godmania or Cybistax but does not agree 1992). The flowers of Tabebuia group I are white to in other particulars.’’ This species was later moved red in color, and often have a yellow throat (Fig 1I). to Cybistax by Seibert (1940). However, Miranda Two species belonging to this clade, Tabebuia aurea (1965) transferred this species to a new genus, and the unsampled Tabebuia nodosa have yellow Roseodendron, segregating it from Cybistax on the flowers but otherwise share the above character- basis of calyx texture and shape, sessile nature of istics. its ovary, and indumentum of branched hairs. Tabebuia group II can be distinguished by having Grose and Olmstead (2007) conducted a molecu- an indumentum of simple to stellate or dendroid lar phylogenetic study of the Tabebuia Alliance, hairs (Fig. 1A, D). Lepidote scales are also usually those Neotropical Bignoniaceae with palmately- present, but may be obscured by the hairs. The compound leaves. That study included 25% of all calyx is campanulate to cupular and 5-dentate Tabebuia species and had representatives from all (Fig. 1D). The wood is among the heaviest and 10 of Gentry’s (1992) species groups. The findings hardest known, with a basic specific gravity showed that Tabebuia consists of three clades. greater than 0.74 (dos Santos and Miller 1992). It ‘‘Tabebuia goup I’’ is sister to the Caribbean is also distinctive among Tabebuia s. l., in having endemic Ekmanianthe.‘‘Tabebuia group II’’ is sister very large pits (ranging from 7–14 mm) in their to Crescentieae+Spirotecoma. The third clade is vessel elements (dos Santos and Miller 1992). Only represented by T. donnell-smithii and is sister to two species in this group, T. pumila and T. Tabebuia group II +Crescentieae+ Spirotecoma. selachidentata, are described as occasionally having unifoliolate leaves (Gentry 1992). In all other cases, MATERIALS AND METHODS the leaves are digitately 3–9 foliolate. The fruits in this group are linear and slightly costate to smooth, Characters to support the phylogeny of Grose and Olmstead (2007) are based on herbarium holdings at US, and often are densely tomentose. The flowers in MO and NY and published morphological and anatomical Tabebuia group II are generally yellow (Fig. 1G) or, studies (Gentry 1992; dos Santos and Miller 1992). Herbarium in four species, T. selachidentata, T. barbata, T. specimens were consulted for morphological characters heptaphylla and T. impetiginosa, magenta with (Appendix 1). Leaf surfaces and calices were examined with a scanning electron microscope (SEM). Specimens were yellow throat (Gentry 1992). prepared for the SEM according to the protocol established Tabebuia donnell-smithii represents a group dis- in Matthews and Endress (2004) tinguished by its unique calyx (Fig. 1E). It is spathaceous in shape, and of the same color and MORPHOLOGICAL CHARACTERS DEFINING CLADES texture as the corolla. This lineage contains only one other species, T. chrysea. The indumentum is of Each of the three clades of Tabebuia: Tabebuia lepidote scales and small, glandular hairs (Fig. 1B). groups I and II and T. donnell-smithii is supported The wood is similar to that of Tabebuia group I but by several morphological characters. Gentry de- contains tyloses, or intrusive growths of the cell scribed the importance of the calyx in Bignoniaceae wall into the vessel cavities, and pits intermediate taxonomy especially in tribe Bignonieae (Gentry in size between those of Tabebuia groups I and II 1980). This study confirms previous observations (dos Santos and Miller 1992). The corolla is yellow that calyx morphology as well as indumentum, (Fig. 1H), occasionally with thin red lines, and wood anatomy, flower color, and fruit morphology fruits are linear and irregularly costate and bullate.