Cucumis (Cucurbitaceae) must include Cucumella, Dicoelospermum, Mukia, Myrmecosicyos, and Oreosyce: a recircumscription based on nuclear and plastid DNA data

Recent molecular studies have revealed that the genus Cucumis in its current circumscription is paraphyletic. To become monophyletic, Cucumis must include five genera of the subtribe Cucumerinae, namely Cucumella, Dicoelospermum, Mukia, Myrmecosicyos, and Oreosyce, already regarded as closely related by earlier workers based on morphology. The 19 species in the five genera are here formally transferred to Cucumis, resulting in 14 new combinations, two changes in status, and three new names (Cucumis indicus, C. kirkbrideana, and C. oreosyce). A description of the genus and a key to its 52 species are given, and the subgenera and sections are recircumscribed to reflect monophyletic groups. Subgenus Humifructus, with a haploid chromosome number of 12, contains only C. humifructus and C. hirsutus, while subgenus Cucumis, with n = 12 or n = 7, contains the remainder of the species. The latter is further divided into the sections Aculeatosi, Cucumella, Cucumis, Metuliferi, and Sagittati.