Circumscription of Malvaceae (Malvales) as determined by a preliminary cladistic analysis of morphological, anatomical, palynological, and chemical characters

We report a phylogenetic analysis of ''core'' Malvales (Tiliaceae, Sterculiaceae. Bombacaceae, and Malvaceae) based on morphological, anatomical, palynological, and chemical features. The results of the analyses lead to the conclusion that Tiliaceae, Sterculiaceae. and Bombacaceae, as variously delimited, are paraphyletic: only the Malvaceae are likely monophyletic. The genera of ''core'' Malvales form a well-defined clade. Genera of ''Tiliaceae'' constitute the basal complex within ''core'' Malvales. The ''Sterculiaceae'' (most genera) + ''Bombacaceae'' + Malvaceae Form a clade on the basis of a monadelphous androecium: ''Bombacaceae'' + Malvaceae also form a clade, which is diagnosable on the basis of monoloculate anthers. It is clear that the traditional classification, with its arbitrarily delimited evolutionary grades, is unsatisfactory, especially if one seeks to reflect phylogeny accurately. Thus, Malvaceae is redefined to refer to the most recent common ancestor of plants previously considered to be ''Tiliaceae,'' ''Sterculiaceae,'' ''Bombacaceae.'' and Malvaceae, and all of the descendants of that ancestor. This broadly circumscribed Malvaceae can be diagnosed by several presumed synapomorphies, but we draw special attention to the unusual floral nectaries that are composed of densely packed, multicellular glandular hairs on the sepals (or less commonly on the petals or androgynophore).