Section Brachyandra, one of 13 sections of Cuphea, is exceptional in comprising the majority of self-fertilizing species in the genus; most other Cuphea, although self-compatible, are protandrous outcrossers. The section is defined by presence of stamens with short filaments deeply inserted in the floral tube, characters directly tied to autogamy. There are few differences in floral morphology among the species and vegetative features arc variable and overlapping. The close similarities may be attributed to recent speciation within a monophyletic group that is defined by the acquisition of this reproductive mode, or the section may be polyphyletic, with the similarities the results of convergence driven by the change from outcrossing to selling. Seed and pollen morphology, previously undescribed in this group, suggest that sect. Brachyandra is not monophyletic but comprises a minimum of three different evolutionary lines: 1) four species with winged seeds and oblate, syncolporate, striated pollen with protruding pores; 2) two species with large non-winged seeds and psilate pollen without protruding pores and with slight interaperturate thickenings; 3) eight species with small non-winged seeds and nearly spheroidal, non-syncolporate, psilate to rugulate pollen. Variation in thc last group suggests it is derived from more than one ancestor. In cladistic analysis, the species of section Brachyandra oçcur wilhin clades of species from sections Euandra, Pseudocircaea, Trispennuin, and Amazoniana. Results indicate that there is no sound phylogenetic basis for continued recognition of sect. Brachyandra as it is prcsently defined.
Lythraceae; Cuphea; Brachyandr; self-fertilizing species; cladistic analyses