The subfamilial and tribal classification of the family Asclepiadaceae

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 Tybphora 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.

On the Generic Circumscription of <I>Gonolobus</I> (Apocynaceae, Asclepiadoideae): Evidence from Molecules and Morphology

“…Of the characters listed as typical for the subtribe (Liede 1997, following, e.g., Stevens 1988, Kunze 1995and Swarupanandan & al. 1996, all species possess the broad, flat style-head and strongly divergent pollen sacs.…”

Secretory Tissues and the Morphogenesis and Histochemistry of Pollinarium in Flowers of Asclepiadeae (Apocynaceae)

“…Members of this group present flowers with an apocarpous ovary and the upper portion of the styles postgenitally fused, forming the style head (Fallen 1986;Endress 1994;Swarupanandan et al 1996). The filaments are connate, forming a tube, and the anthers are free from one another but postgenitally adnate to the lower portion of the style head through the retinaculum, giving rise to the gynostegium and a complex pollination system (Rao and Ganguli 1963;Fallen 1986;Endress 1994;Swarupanandan et al 1996;Endress and Bruyns 2000).…”

“…The filaments are connate, forming a tube, and the anthers are free from one another but postgenitally adnate to the lower portion of the style head through the retinaculum, giving rise to the gynostegium and a complex pollination system (Rao and Ganguli 1963;Fallen 1986;Endress 1994;Swarupanandan et al 1996;Endress and Bruyns 2000).…”

“…In all species of the family, the style head has a secretory epidermis (Fallen 1986;Kunze 1993Kunze , 1994. In Asclepiadoideae, the style head is responsible for the secretion of the translator, which is composed of one corpusculum and two caudicles (Vijayaraghavan and Cheema 1977;Schnepf et al 1979;Kunze 1993Kunze , 1994Endress 1994;Swarupanandan et al 1996).…”

“…The translator has a very constant morphology in the different taxa and has been used to classify the genera at the infratribal or tribal level (Volk 1950;Kunze 1995;Swarupanandan et al 1996;Endress and Bruyns 2000). However, few studies have analyzed its chemical composition and mor-1 E-mail: diegodemarco@usp.br.…”