A Monograph of Sida Sect. Oligandrae (Malvaceae)

Abstract

Sida L. sect. Oligandrae Clement is markedly distinct from the rest of the rather large genus. It is characterized by large and deeply lobed leaves, and mericarps with long, protruding, clinging awns. Glandular trichomes are often abundant and have been found to be lethal to insects (Burandt 1991). The species are all geographically clustered in the middle Andes. However, as is often the case with such a discrete group, the component species have been difficult to discriminate. Nine species have been described for the section: S. palmata Cav. (Cavanilles 1785), S. ricinoides L'Her. and S. jatrophoides L'Her. (L'Heritier 1789 but dated 1785), S. oligandra Schumann (Schumann 1890), S. lomageiton Ulbr. and S. rupo Ulbr. (Ulbrich 1916), S. lomana Bruns (Bruns 1929), and S. decandra R. E. Fries and S. patuliloba R. E. Fries (Fries 1947). The interpretation of these nine species has varied greatly but comprehensive treatments have retained seven or eight (Clement 1957; Fries 1947; Kearney 1958; MacBride 1956). For each of these treatments, pronounced scarcity of material and a failure to examine types have resulted in an unsatisfactory taxonomic resolution of the species. Field observations were essentially non-existent and species distributions cursorily figured from specimen annotations produced an untenable picture of the group's biogeography. In the present study, these difficulties have been addressed by an examination of nearly all types and the addition of new collections and numerous field observations. Four species, circumscribed by their ecologies as well as morphological characters, were resolved. The species were most easily distinguished by their fruits, whereas vegetative characters were sufficient to distinguish among all but a few specimens. The low stamen number of one species is unique within the genus and the absence of stipules in two species is exceptionally rare in the Malvaceae.