Generic Relationships in the Dichrostachys Group (Leguminosae: Mimosoideae): Evidence from Chloroplast DNA Restriction Sites and Morphology

Abstract

Data from chloroplast DNA restriction sites and morphology are combined in a phylogenetic analysis of six genera in the Dichrostachys and Leucaena groups. Desmiianthus is demonstrated to be monophy- letic, which contrasts with previous morphological studies in which it was paraphyletic to Neptunia. The monotypic genus Calliandropsis from central Mexico is sister to the Old World genus Dichrostachys, a result consistent with all previous analyses, as well as with ecological evidence. The cladistic analysis shows that the Dichrostachys group is not monophyletic; Desmanthus is more closely related to Leucaena and Schleinitzia than it is to the other genera in the Dichrostachys group. Based on these data, the Leucaena group is recircumscribed to include the genera Desmanthus, Leucaena, and Schleinitzia, and the Dichrostachys group to include Calliandrop- sis, Dichrostachys, Gagnebina, and Alantsilodendron. The position of Neptunia relative to the other genera is ambiguous, and it is placed incertae sedis pending more conclusive evidence about its position in the Mimosoideae. In 1981, Lewis and Elias realigned genera in the legume tribe Mimoseae (Mimosoideae) by infor- mally recognizing 12 groups. One of these groups was the Dichrostachys group, consisting at the time of four genera: Desmanthus, Dichrostachys, Gagne- bina, and Neptunia. Two segregate genera were subsequently recognized as belonging to the group: