Recognition of Aphelandra glabrata (Acanthaceae) from Western South America, with Notes on Phylogenetic Relationships

Abstract

Aphelandra glabrata is a highly distinctive member of the A. pulcherrima complex. Within this monophyletic group, A. glabrata belongs to a phylogenetic lineage that is marked by extrafloral (bracteal) nectary patches composed of numerous minute (<0.1 mm in diam.) glands. The species occurs in western South America, from central Colombia south into Peru and Bolivia. Aphelandra pulcherrima (with which A. glabrata has previously been combined) differs from this species in numerous features (e.g., nectary morphology, corolla vestiture, stigma morphology, and pollen morphology), and belongs to a different lineage within the A. pulcherrima complex. Aphelandra pulcherrima is a species of northern South America, occurring in northern Colombia, Venezuela, Trinidad, Guyana, and Surinam. Progress toward a monographic treatment of the approximately 40 members of the Aphelan- dra pulcherrima complex (sensu McDade 1984) requires recognition of A. glabrata Willd. ex Nees as distinct from A. pulcherrima Kunth. This change, together with recognition of the Cen- tral American plants formerly assigned to A. pulcherrima (Leonard 1938; Wasshausen 1975) as A. leonardii McDade (McDade 1982), clarifies the apparently extreme morphological variability within A. pulcherrima and reduces its range to northern Colombia, Venezuela, Trinidad, Guy- ana, and Surinam. Distinguishing these species further emphasizes the existence of at least two major monophyletic lineages within the A. pul- cherrima complex, with the newly recognized taxa A. glabrata and A. leonardii correctly placed in one lineage, and A. pulcherrima placed in the other, as described and figured below. Clarifi- cation of this taxonomic problem is especially important given that several floristic works cur- rently in progress in northern South America will near completion before a monographic treatment of the entire group can be published.