SYSTEMATIC STUDIES OF THE GENUS SIPHONOGLOSSA SENSU LATO (ACANTHACEAE) (CHEMICAL SYSTEMATICS, PALYNOLOGY, JUSTICIA)

A series of systematic studies of the genus Siphonoglossa (Acanthaceae), a genus not previously monographed, are presented. These studies utilize data from comparative morphology, cytology, palynology and flavonoid chemistry to examine the tribal and subtribal classification and generic delimitation of Siphonoglossa. Because of morphological disparity within the genus, it was suspected that Siphonoglossa sensu lato was an artificial assemblage of taxa grouped together because of a single-character phenetic relationship based on apparent convergence of corolla morphologies. The classification of the genus into two sections, the type section and section Pentaloba, and an informal subgeneric category is discussed in reference to the presently proposed generic and tribal classification.; Data are presented from palynological studies that demonstrate that Siphonoglossa was incorrectly classified in the tribe Odontonemeae because of a misinterpretation of pollen morphology in the group and that the taxa of sections Siphonoglossa and Pentaloba correctly belong in the tribe Justicieae, while the taxa of the informal category do belong in Odontonemeae. Even with the tribal-level disparity removed, however, the genus as composed of the two sections still appeared artificial. The relationships of the sections were therefore critically investigated through cytology and comparative flavonoid chemistry. The results revealed that section Siphonoglossa has a base chromosome number of x = 11 and elaborates only apigenin-based C-glycosylflavones, while section Pentaloba has a base chromosome number of x = 14 and produces flavonol O-glycosides of quercetin and isorhamnetin.; Because of these wide differences between the sections, it is proposed that Siphonoglossa be restricted to the taxa of the type section (= Siphonoglossa sensu stricto), while the taxa of section Pentaloba be transferred to the genus Justicia. Additionally, other taxa placed in Siphonoglossa are treated and it is proposed that they too be excluded from the genus for various reasons. A peripheral study of the small genus Yeatesia is included because one of its species was mistakenly allied with Siphonoglossa; the study of Yeatesia utilizes the same types of data as gathered for Siphonoglossa.