Phylogenetic patterns in the tribe Acacieae (Caesalpinioideae: Fabaceae) based on rbcL, matK, trnL-F and ITS sequence data

Abstract

The tribe Acacieae is one of the three tribes of the distinct mimosoid clade nested within the re-circumscribed sub-family Caesalpinioideae. Many uncertainties exist with the taxonomic status of tribe Acacieae in relation to tribe Ingeae and genus Acacia. To unravel the phylogenetic patterns within Acacieae, nine members of the tribe were phylogenetically analysed employing both parsimony and Bayesian methods. Six data matrices (ITS, rbcL, matK, trnL-F, rbcL+matK+trnL-F and ITS+rbcL+matK+trnL-F) representing 46 sequences, and 2 outgroup taxa were used for the analysis. Our results are in support to some previous studies on the phylogeny of the Acacieae. It supports the polyphyly of tribe Acacieae. The monophyly of Vachellia, Senegalia and Faidherbia taxa were strongly supported at >70% bootstrap support values and >0.90 bayesian inference. An unresolved basal paraphyletic clade of Acacia auriculiformis with the outgroup taxa was shown in all the datasets, at mostly low support values. Faidherbia albida was nested within the Senegalia grade while A. auriculiformis (Acacia s.s.) was the closest taxon to the outgroup taxa. A key finding of this study is the polyphyly of Albizia and its close association with A. auriculiformis.