Phylogeny, classification and biogeography of Philotheca sect. Erionema (Rutaceae) based on nrDNA sequences

Abstract

ABSTRACT Philotheca sect. Erionema includes 14 species from eastern Australia and one from south-western Australia. We conducted a phylogenetic analysis of the section, including samples of all species, using sequences of the ITS and ETS regions of nuclear ribosomal DNA. Results were broadly congruent with a previous analysis based on morphological and flavonoid data. The analysis is consistent with the monophyly of the section and supports the monophyly of six species represented by multiple samples. Philotheca verrucosa (A. Rich.) Paul G. Wilson was resolved as paraphyletic with respect to P. freyciana Rozefelds but with poor support. Philotheca glasshousiensis, P. myoporoides and P. myoporoides subsp. myoporoides were clearly polyphyletic, including separate geographic clades and the classification of each of these taxa requires revision. In particular, disjunct northern populations of P. glasshousiensis probably represent a distinct species, the five subspecies of P. myoporoides could be treated as separate species and at least two other distinct groups that are currently included under the circumscription of subsp. myoporoides could be treated as species. The phylogeny revealed deeply divergent, geographically overlapping clades in eastern Australia and substantial distances (up to 900 km) between sister taxa. We infer that biogeography of the group has been shaped largely by vicariant differentiation of taxa.