Phylogeny of the Neotropical legume genera Zygia and Marmaroxylon and close relatives

Abstract

AbstractThe Neotropical legume genera Zygia and Marmaroxylon have traditionally been considered closely related and are sometimes treated as congeners. They have been referred to the mimosoid tribe Ingeae based on their possession of flowers with basally fused stamen filaments. However, their systematic status and position have not been analysed in a phylogenetic context. This study provides the first molecular phylogeny of Zygia and Marmaroxylon and closely related mimosoid legume genera, particularly from the tribe Ingeae. DNA sequence data were derived from the nuclear external transcribed spacer (ETS) and the internal transcribed spacer (ITS), and from the chloroplast psbA‐trnH and trnL‐trnF regions, and were analysed using Bayesian inference. In all, 29 species of Zygia and 7 species of Marmaroxylon were included in the study along with representative species from the closely related genera Abarema, Acacia s.str., Archidendropsis, Calliandra, Chloroleucon, Cojoba, Faidherbia, Havardia, Hydrochorea, Inga, Leucochloron, Macrosamanea, Pithecellobium, Pseudosamanea, Samanea, Senegalia, Vachellia and Zapoteca. The results show that neither Zygia nor Marmaroxylon are monophyletic as presently circumscribed. Furthermore, these two genera are not monophyletic together. None of the nine presently recognized sections of Zygia that contain more than one species are shown to be monophyletic. Two of the monospecific sections of Zygia, sect. Ingopsis (Z. inundata) and sect. Pseudocojoba (Z. sabatieri), were found in a clade together with species of Inga. Marmaroxylon ocumarense and M. magdalenae, previously treated as synonyms (as Zygia), are not conspecific, and are found in a clade with Macrosamanea and in a clade with species of Abarema and Hydrochorea, respectively. Our results also show the Inga alliance to be non‐monophyletic. In correspondence with the results presented, all species referred to Marmaroxylon, except for M. ocumarense and M. magdalenae, are here included in Zygia, and Z. inundata is treated in Inga, in which genus it was first described.