Spyridium Fenzl is a genus of ~45 species endemic to south-western and south-eastern Australia. This study provides the most comprehensive phylogenies of Spyridium to date, analysing both entire chloroplast genomes and the nuclear ribosomal array (18S–5.8S–26S). There was substantial incongruence between the chloroplast and nuclear phylogenies, creating phylogenetic uncertainty, but some clear relationships and biogeographic patterns could be established. Analyses support the monophyly of Spyridium, identifying an early east–west split at the base of the nuclear phylogeny and deep divergences of New South Wales and Tasmanian endemic clades. We also found evidence of more recent dispersal events between eastern and western Australia and between Tasmania and the mainland. Eleven taxa were found to be monophyletic in the nrDNA phylogeny and two were clearly polyphyletic (S. eriocephalum Fenzl and S. phylicoides Reissek). Although the polyphyly of S. eriocephalum correlates with the two varieties, suggesting distinct taxa, further research is required on S. phylicoides.

Seventeen Australian, phyllodinous species of Acacia s.s. (from sections Juliflorae and Phyllodineae) were analysed to test the monophyly and relationships of ‘the Acacia longifolia group’, an informal group recognised in the Flora of Australia. Analyses were based on both morphological and molecular data, with A. triptera as an outgroup. A total of 92 herbarium specimens was investigated, with 15 phyllode, inflorescence, flower, pod and seed characters scored. The ITS and ETS regions of nuclear rDNA were sequenced and combined with a larger dataset sampled from species of all major clades of Acacia, totalling 65 accessions. Cladistic analyses provided evidence of a clade that defines the A. longifolia group as follows: A. alpina, A. axillaris, A. courtii, A. dallachiana, A. derwentiana, A. floribunda, A. longifolia subsp. longifolia and A. longifolia subsp. sophorae, A. longissima, A. maidenii, A. mucronata, A. obtusifolia, A. orites, A. oxycedrus, A. phlebophylla, A. rhigiophylla and A. riceana (all sect. Juliflorae), but excluding A. verticillata (section Juliflorae) and A. genistifolia (section Phyllodineae). The A. longifolia group is recognised as including south-eastern Australian species with cylindrically spiked inflorescences and phyllodes with prominent anastomosing venation.

We assembled the complete chloroplast genome of the Australian shrub Spyridium parvifolium var. parvifolium . The genome was 161,012 bp in length, with a pair of inverted repeats (IRs) of 26,515 bp, separated by a large single copy (LSC) region of 88,814 bp and a small single copy region (SCC) of 19,168 bp. The GC content was 36.9%. In total, 130 genes were annotated, including 86 protein coding genes, 36 tRNA genes and 8 rRNA genes. Phylogenetic analysis of 56 chloroplast genes placed this genome of S. parvifolium var. parvifolium within the family Rhamnaceae.

Spyridium parvifolium is a widespread and morphologically variable shrub from south-eastern Australia. Several varieties have been recognised, and there is disagreement on the accepted taxonomy between Australian states. This study investigated the phylogeography of the species and assessed genetic distinctiveness of its morphological variants. Nuclear ribosomal DNA and complete chloroplast genomes from seventy-two samples of S. parvifolium and seven samples from closely related species were sequenced and analysed using both Bayesian and maximum likelihood phylogenetic methods. The results showed incongruence in the placement of several associated taxa (S. cinereum, S. obcordatum and S. daltonii), plausibly due to long branch attraction, introgression or incomplete lineage sorting. Spyridium parvifolium was resolved as paraphyletic in both phylogenies, with accessions from west of the Murray Darling Depression divergent from those east of the Depression. We found evidence of isolation within S. parvifolium on the inland side of the Great Dividing Range and recent gene flow across Bass Strait. The variants of S. parvifolium were not supported as genetically distinct, and with the prevalence of several variants at single sites and morphological intergrades between variants, we conclude that the taxon is a single, morphologically variable species and that no infraspecific classification is warranted.