A Chloroplast DNA Based Phylogeny of the Malvaceae

Abstract

The classification and phylogenetic relationships of the genera within the Malvaceae have received little recent attention despite the widespread distribution of the family and the economic importance of some of its members. Traditional classifications have utilized morphological, biogeographical, and chromosomal data. We have mapped the chloroplast genome from 23 of the approximately 110 genera of Malvaceae, representing four of the five tribes. Six equally most parsimonious phylogenetic reconstructions resulted from parsimony analysis of 236 variable restriction sites. Members of the Hibisceae and Malvavisceae did not form monophyletic groups, while members of the Gossypieae and Malveae did form monophyletic The Abutilon alliance formed a sister group to the remainder of the Malveae. Members of other alliances within the Malveae did not form the monophyletic groups proposed in the classical literature. The Malvaceae are a worldwide family with a primary concentration of genera in the tropical regions. There are approximately 110 genera and over 2,300 species divided into five tribes: Decaschistieae, Gossypieae, Hibisceae, Malvavisceae, and Malveae. Previous workers have made strong statements supporting recognition of the tribal units in the Bates and Blanchard (1970, p. 927) stated about the tribes: In an evolutionary sense these tribes probably have been long distinct and thus should be considered separately when evaluating most kinds of relationships within the family. Fryxell (1975, p. 172) stated: Although exceptions are known for certain characters given in the table, these exceptions do not detract from the conclusions that the tribes are natural groups. Both were speaking of the then four recognized tribes. Fryxell (1975) went on to describe the fifth tribe: Decaschistieae. The tribes range in size from the Decaschistieae with only one genus, to the Malveae with nearly 70 genera. Many authors have discussed the circumscription of the family (e.g., Edlin 1935; Kearney 1951; Bates 1968; Fryxell 1968a). They have primarily focused on two issues: 1) how the Malvaceae differ from the other families in the Malvales, and 2) how the genera within the family are related. We will concentrate on the second issue in this paper. Tribal circumscription in Malvaceae currently is based on morphological, chromosomal, and biogeographical data. Fryxell (1968a) summarized the nomenclatural history of the Gossypieae and the Hibisceae and argued strongly for retaining the members of these tribes in the Malvaceae. Fryxell (1975) provided supportive evidence for the recognition of the new tribe Decaschistieae. Some of the most detailed work with genera in the Malvaceae has been with the Malveae by Bates (1968) and Bates and Blanchard (1970). These papers used morphological, biogeographical, and chromosomal data to divide the Malveae further into informal groups called alliances. These are not nomenclaturally recognized categories but serve to associate related taxa. The objectives of this study were to test hypotheses of monophyly of groups in the Malvaceae, with particular emphasis on the intergeneric relationships in the Malveae. Data from chloroplast DNA (cpDNA) restriction site mapping are used to hypothesize phylogenetic relationships. MATERIALS AND METHODS Representatives of four of the five tribes were sampled (Table 1). A single species was sampled