The Application of a Cladistic Analysis to the Classification and Identification of Weinmannia (Cunoniaceae) in Madagascar and the Comoro Islands
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The application of a cladistic analysis to the classification and identification of Weinmannia (Cunoniaceae) in Madagascar and the Comoro Islands Jason C. BRADFORD Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166-0299, U.S.A. [email protected] ABSTRACT Weinmannia species from Madagascar are currently difficult to identify with KEY WORDS available published accounts due to both a paucity of qualitative characters Weinmannia, used in identification keys, and a large number of undescribed species. Cunoniaceae, cladistics, However, newly recognized morphological characters, especially of the inflo- classification, rescence, can be used to diagnose Malagasy sect. and species-groups. These taxonomic keys, characters, used previously for a comprehensive cladistic analysis of the genus inflorescence, Madagascar, Weinmannia (BRADFORD 1998), are applied here in diagnoses and a key to Comoro Islands. the resulting sections and species-groups of Weinmannia in Madagascar. RÉSUMÉ Application d’une analyse cladistique à la classification et l’identification des Weinmannia (Cunoniaceae) à Madagascar et aux Comores. Les espèces malgaches de Weinmannia sont actuellement difficiles à identifier avec les publications disponibles en raison à la fois de la pauvreté des caractères MOTS CLÉS qualificatifs utilisés dans les clés d’identification et d’un nombre élevé d’espèces Weinmannia, non décrites. Cependant, des caractères morphologiques nouvellement recon- Cunoniaceae, cladistique, nus, en particulier ceux de l’inflorescence, peuvent êre utilisés pour les dia- classification, gnoses des sections et des groupes d’espèces malgaches. Ces caractères, clés taxonomiques, employés précédemment pour une analyse cladistique du genre Weinmannia inflorescence, Madagascar, (BRADFORD 1998) sont appliqués ici dans les diagnoses et une clé de détermi- Comores. nation des sections et groupes d’espèces de Weinmannia à Madagascar. INTRODUCTION BARNES 2001), is represented in Madagascar solely by its largest genus, Weinmannia L., with Cunoniaceae, a southern hemisphere family c. 150 species worldwide. Most Weinmannia with 26 genera and c. 300 species (BRADFORD & species are trees and shrubs of tropical montane ADANSONIA, sér. 3 • 2001 • 23 (2) : 237-246 © Publications Scientifiques du Muséum national d’Histoire naturelle, Paris. 237 Bradford J.C. forests, although tropical lowland species occur in As exemplified by the number of species found Madagascar, and temperate species in Chile, during field work at Marojejy (BRADFORD & Argentina, Australia, New Zealand and South MILLER 2001), Madagascar is one of the most Africa. Cunonia L. and Platylophus D. Don, from species-dense areas in the world for Weinmannia, South Africa, are the only African members of the with levels of sympatry similar to that found in family. Andean forests. Unlike other parts of the world, Cunoniaceae have been the subject of recent however, the species richness of Malagasy phylogenetic and revisionary investigations, with Weinmannia is accompanied by a diversity of most attention given thus far to Weinmannia morphological characters that enable relatively (BRADFORD 1998; HOPKINS 1998a, 1998b, rapid identification of species. 1998c; HOPKINS & FLORENCE 1998). Based on Study of available herbarium specimens and cladistic studies (discussed below), the infra- field work indicate that 35-40 Weinmannia generic classification of BERNARDI (1961, 1964) species occur in Madagascar, 15-20 more than and the placement of some species has been were known to BERNARDI (1965, 1969). Given slightly modified to make sections mono- the large number of undescribed species and the phyletic. BRADFORD (1998) recognized five sec- limited array of qualitative characters used by tions of Weinmannia that circumscribe species BERNARDI in his keys, it is difficult to identify from the Americas plus two species from the Weinmannia species. The present paper addresses Mascarenes (sect. Weinmannia), Malesia and this problem by: (1) describing and illustrating Melanesia (sect. Fasciculata Bernardi), the South previously overlooked qualitative character varia- Pacific (sect. Leiospermum D. Don), and tion among Malagasy Weinmannia, (2) present- Madagascar and the Comores (sect. Spicata ing a synoptic key to the sections and Bernardi and Inspersa Bernardi; see also HOPKINS species-groups of Weinmannia in Madagascar and 1998a). Taxonomic changes affect a few the Comores, (3) providing diagnostic features Malagasy species. for each section and species-group, and (4) listing Malagasy Weinmannia species were last treated all presently described species in each species- by BERNARDI (1964, 1965, 1969). He estab- group. Because a number of Weinmannia species lished two endemic sections Spicata and Inspersa, remain to be described from Madagascar, it and placed a few species in the more wide- would be premature to write a key to the species spread sections Weinmannia and Leiospermum level. Instead, the key given below aids species- (sect. Leiospermum has priority over BERNARDI’s level identification by reducing the number of equivalent sect. Racemosa, see HOPKINS 1998a). species with which one must compare an uniden- However, BERNARDI’s assignment of some tified specimen. This synoptic key has proven Malagasy-Comoral species to sections normally useful as the basis for a species-level key of found outside of Madagascar has been proven Weinmannia from the Marojejy massif incorrect. Weinmannia baehniana Bernardi and (BRADFORD & MILLER 2001), and could be W. comorensis Tul., which BERNARDI placed in applied to other regions and eventually the entire sect. Leiospermum, belong instead in sect. genus in Madagascar. Spicata, and the species he included in sect. The key and diagnoses are largely based on a Weinmannia, W. rutenbergii Engl. and W. venusta recent morphological cladistic study (BRADFORD Bernardi, belong in sect. Inspersa (see BRADFORD 1998) that found several characters not discussed 1998 and below). Both a morphological cladistic by BERNARDI (1964, 1965). In Madagascar, sev- analysis of Weinmannia species-groups and sec- eral groups of species can be recognized that share tions (BRADFORD 1998) and molecular system- unique combinations of these qualitative charac- atic work on the genus (BRADFORD 2000; ters. The key and diagnoses for the Malagasy BRADFORD & BARNES 2001) support the mono- species-groups utilize inflorescence terminology phyly of sections Spicata and Inspersa as now cir- that may not be familiar. For this reason, figures, cumscribed and provide evidence that they are illustrations and a discussion of important char- sister taxa. acters precede the key. 238 ADANSONIA, sér. 3 • 2001 • 23 (2) Cladistic analysis of Weinmannia (Cunoniaceae) Fig. 1. — Cladogram of Weinmannia species-groups (with representative species) based on morphology (from BRADFORD 1998). The main characters used in the key are plotted on the tree. FROM CLADOGRAMS TO KEYS monophyletic. At present, not enough is known about the phyletic relationships of Weinmannia Prior to conducting a cladistic analysis of species-groups A-G to give them formal taxo- Weinmannia and the related genus Cunonia, nomic names and rank, which would violate the specimens representing all known species of these principles of phylogenetic systematics and proba- genera were examined to find unique combina- bly lead to taxonomic instability. Nevertheless, a tions of qualitative morphological characters real need exists to communicate group informa- among species (see vouchers in BRADFORD 1998). tion on this complex genus, which can be done This process led to the recognition of species- by informally recognizing species-groups A-G for groups, each representing from one to many the purpose of discussion. Such informal tax- species, that served as a terminal units in the onomies have a long history (e.g. BENTHAM & cladistic analysis. Seven species-groups were rec- HOOKER 1862-1883) and are commonly used in ognized in Madagascar and the Comores, five of phylogenetic systematics when cladistic resolu- which have apparent autapomorphies, whereas tion is lacking or clades are poorly supported (e.g. two lack clearly apomorphic features (see charac- Angiosperm Phylogeny Group 1998). By ter states in Fig. 1). Species-groups B, C, D, E, acknowledging uncertainty, informal classifica- and G (see below) may therefore be mono- tions may actually communicate information phyletic, whereas no characters have been found more effectively than do some rigid systems that that support the monophyly of species-groups A require all individuals to be part of a formal taxon and F. at each hierarchical rank. Classifications communicate grouping infor- Cladograms can be applied towards taxonomic mation, but phylogenetic systematics also identification by including in a standard dichoto- requires that formally recognized groups be mous key the qualitative characters of the data ADANSONIA, sér. 3 • 2001 • 23 (2) 239 Bradford J.C. matrix as plotted on a dichotomously branching often organized into compound structures borne tree. The key presented below is organized using on a peduncle, and these are called Inflorescence character states as mapped on the cladogram Modules (IMs). Among sections or species- from more general characters to more specific groups, IMs may have distinct patterns of organi- ones. In other words, synapomorphies of the zation along the main stem. The Total largest clades are used in the first order couplet, Inflorescence (TI) is formed by the architectural followed