A five-marker molecular phylogeny of the Styphelieae (Epacridoideae, Ericaceae) supports a broad concept of Styphelia

Abstract

The Styphelieae is the largest of the seven tribes within the subfamily Epacridoideae Arn. (Ericaceae Juss.). Recent molecular phylogenetic work has resulted in the recircumscription of some genera and the erection of new ones, but several non-monophyletic genera remain. Most of them are concentrated in the well-supported Styphelia–Astroloma clade, which contains species currently assigned to Leucopogon R.Br., Styphelia Sm., Astroloma R.Br., Croninia J.M. Powell and Coleanthera Stschegl. Parsimony and Bayesian analyses of sequence data from four plastid markers (rbcL, matK, trnH–psbA, and atpB–rbcL), and the nuclear ribosomal internal transcribed spacer (ITS) for 207 taxa corroborate the polyphyly of the genera Astroloma, Leucopogon and Styphelia and resolve 12 well supported groups. Of these groups, two can be distinguished by unique morphological features and another six by different character combinations. The remaining groups are morphologically heterogeneous and inconsistent, and not readily distinguishable. A number of species remain ungrouped either because their phylogenetic relationships are not clear or because they do not show strong morphological affinities with the group to which they have a close phylogenetic relationship. Translating the results into a phylogenetic classification is a choice between accepting a single, large genus or at least 12 smaller genera. The first option would result in a heterogeneous assemblage conveying limited morphological information. The multi-generic option would be a better reflection of the morphological diversity of the clade, but would result in many genera lacking readily observable, diagnostic morphological characters. We prioritise the nomenclatural stability inherent in the former approach and advocate expanding Styphelia to include all taxa in the Styphelia–Astroloma clade.