A phylogenetic solution to the Acacia problem

Acacia has a complicated taxonomic history including a recent controversial retypification. We suggest that the entire recent Acacia debate is due to inadequacies of the International Code of Nomenclature (ICN), particularly that it requires that all taxa be classified in ranks. The ICN system was not designed for phylogenetic classification and the Acacia nomenclatural fallout reflects this shortfall. We recommend an alternate phylogenetic classification based on the PhyloCode. We propose the name Acacia for the most inclusive clade including the non-monophyletic ICN-based genus Acacia s.l., thereby retaining the name Acacia for use on all descendant lineages including Mimosa and Ingeae. Additionally we provide PhyloCode-based names for five monophyletic lineages of genus Acacia s.l. but not for a sixth until additional information is available. This rankless phylogenetic classification system provides an elegant solution to the Acacia controversy and provides stable, relevant information about this branch of the tree of life.