The subfamilial and tribal classification of the family Asclepiadaceae

Abstract

Abstract A modified classification of the family Asclepiadaceae R. Br. s.s . into three tribes — Secamoneae, Asclepiadeae s.l . and Stapelieae s.l . — is proposed. The position of attachment of the caudicles to the pollinia is suggested as a criterion for defining the erect and pendulous stature of the pollinaria. The concept of the transverse stature of pollinaria has been abandoned. In addition to the stature of the pollinaria, the morphology of the anther sacs (whether or not embedded in the tissue of the anther wings) and the position of anther wings with respect to the anther sacs are suggested as supplementary characters for tribal classification of the family. The characters of the gynoecium, particularly the presence or absence of true styles and the sharp constriction between stigma-head and ovaries (i.e. clavuncular morphology) have also been suggested as useful in differentiating Asclepiadeae s.l . and Stapelieae s.l ., along with the stature of the pollinaria. The circumscription of Asclepiadeae is emended to accommodate taxa of the former tribe Gonolobeae as a subtribe. The circumscription of Stapelieae has been retained in a wider sense, as suggested by Decaisne (1844). The tribes Fockeeae Kunze, Liede & Meve (1994), Marsdenieae Benth. (1876), Ceropegieae Benth. (1876), and Stapelieae s.s . sensu Benth. (1876; non Decne., 1844) have been relegated to subtribe status in the tribe Stapelieae Decne. (1844). Homology of the different parts of the gynoecium in the Asclepiadeae ( s.l .) with those in the Stapelieae ( s.l .) has been drawn. Segments of the style have been distinguished into ‘true style’ and ‘pseudostyle’, the former as parts of the ovary segment in development, the latter as stigma segment in development. The genus Tylophora R. Br. which was formerly treated under Stapelieae Decne. has been transferred to Asclepiadeae based on the morphology of the pollinaria, gynoecium and seed coat architecture.