Big trees of small baskets: phylogeny of the Australian genus

Abstract

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.

Phylogeography and classification of Dusty Miller (Spyridium parvifolium; Rhamnaceae): a morphologically variable shrub from south-east Australia

“…In total, 213 individuals representing 49 species of Spyridium and three outgroup genera of tribe Pomaderreae (Pomaderris, Cryptandra and Trymalium) were sampled, including several phrase name taxa. Of these, 66 samples were newly sequenced accessions of S. parvifolium (64 samples) and S. daltonii (two samples) and 145 were previously included in Clowes et al (2022).…”

“…Seventy-two samples of S. parvifolium from 36 locations were included in this study (Table 1; Fig. 3), of which eight were also included in Clowes et al (2022). Samples were collected from across the geographic range and morphological variants of the species.…”

“…Three samples of S. daltonii were also included, collected from two different locations within the Grampians ranges: Grampians Road and Mt William (Table 1). One of these accessions was also included in Clowes et al (2022).…”

“…Hauenschild et al (2016) included three samples of S. parvifolium in a phylogeny of Rhamnaceae with the combined nrDNA (ITS) and cpDNA (trnL-trnF) analysis placing all three samples in a clade with S. daltonii and S. thymifolium. More recently, Clowes et al (2022) included eight samples of S. parvifolium in a molecular (nrDNA and chloroplast genomes) phylogeny of Spyridium, with the species found in an unsupported clade (Bayesian posterior probability, 0.73) with S. daltonii, S. obcordatum and S. cinereum in the nrDNA phylogeny and resolved in a strongly supported clade (polytomy; Bayesian posterior probability, 1.0) with S. daltonii in the cpDNA tree. The three most closely related species in the nrDNA tree are narrow range endemics with overlapping (or nearly so) distributions with S. parvifolium (Fig.…”

“…The current study aims to extend the work of Clowes et al (2022), with a specific focus on S. parvifolium. Spyridium parvifolium is sampled from across its geographic range, including all named varieties and known morphological variants (VicFlora 2021), together with representatives of other species of Spyridium.…”