A cladistic analysis of the plant family Onagraceae

A cladistic analysis of Onagraceae was performed using 17 characters from morphology, anatomy, palynology, embryology, and cytology, with its 16 genera as the terminal taxa, and with several possible outgroups within Myrtales. In the main analysis (all Myrtales as outgroup), seven equally parsimonious cladograms were produced, each with 29 steps and a consistency index of 0.82. A successive weighting procedure was applied, resulting in six cladograms with a consistency index of 0.93. All cladograms share the following nine monophyletic groups: 1) all taxa except Ludwigia; 2) Circaea (Fuchsia-Lopezia); 3) Fuchsia-Lopezia; 4) Gayophytum (Epilobium-Boisduvalia) (Gongylocarpus-Xylonagra-Camissonia (Clarkia (Hauya-Calylophus-Gaura)) (Oenothera-Stenosiphon)); 5) Epilobium-Boisduvalia; 6) Gongylocarpus-Xylonagra-Camissonia (Clarkia (Hauya-Calylophus-Gaura)) (Oenothera-Stenosiphon); 7) Clarkia (Hauya-Calylophus-Gaura); 8) Hauya-Calylophus-Gaura; and 9) Oenothera-Stenosiphon. One additional monophyletic group appears after applying the successive weighting procedure: Gayophytum (Epilobium-Boisduvalia). Results of the cladistic analysis support a sister group relationship of Ludwigia to the rest of the genera. The clade of Circaea, Fuchsia, and Lopezia is the sister group of the remaining genera (except Ludwigia), but there is relatively less resolution of the relationships among those genera (the tribes Onagreae, Epilobieae, and Hauyeae). The other main conclusions are that the positions of Hauya and Gayophytum are problematic and not well resolved, and that the tribe Onagreae may be paraphyletic