A Revision of Cuphea Section Brachyandra s. s. (Lythraceae)

Abstract

This morphologically-based study of the New World genus Cuphea section Brachyandra is part of a revision-in-progress of the 1903 monograph of Cuphea by E. Koehne. The section is narrowly defined here as comprising annual and perennial herbs and subshrubs with floral tubes 3–9(-11.5) mm long, stamens deeply inserted, and anthers positioned proximal to the sinuses of the sepals. Thirteen species and three varieties are recognized. Four species are widely distributed in the New World, five are endemic to the Caribbean region, and four species and two varieties are restricted to South America. The revision includes a morphological overview, seed oil composition and chromosome number data, a key to the species, species descriptions, illustrations, and distribution maps. Neotypes are designated for: Cuphea balsamona Cham. and Schltdl., C. fuscinervis Koehne, C. urens Koehne, and Lythrum carthagenense Jacq. Lectotypes are designated for: Cuphea section Brachyandra Koehne, C.calophylla Cham. and Schltdl., C. calophylla var. calophylla f. deformis Koehne, C. orthodisca Koehne, C. anisophylla Hemsl., C. mesostemon Koehne, C. elliptica Koehne, and C. pustulata Koehne. New combinations are: C. calophylla var. fuscinervis (Koehne) S. A. Graham and C. calophylla var. mesostemon (Koehne) S. A. Graham. Relationships of the species are discussed based on evidence from morphology and available molecular phylogenetic studies. The section, although narrowly defined, remains polyphyletic. It is represented by at least three lineages differing in pollen and seed morphology, and occurring in three of the five major clades of the genus. Two of the three lineages, with South American origins, have given rise to the five species of sect. Brachyandra endemic to the Antilles.