PREMISE OF THE STUDY: Continental-scale disjunctions and associated drivers is a core research interest in biogeographic studies. Here, we selected a species-rich Australian plant genus (Calytrix; Myrtaceae) as a case study to investigate these patterns in an Australian context. The endemic Australian starflower genus has a disjunct distribution across the mesic fringes of the continent and is absent from the arid centre.

METHODS: We used high-throughput sequencing to generate unprecedented resolution and near complete species-level nuclear and plastid phylogenies for Calytrix. BioGeoBEARS and biogeographic stochastic mapping (BSM) were used to infer ancestral areas, the relative contributions of vicariance and dispersal events, and directionality of dispersal.

KEY RESULTS: Present-day disjunctions in Calytrix are explained by a combination of scenarios: (1) retreat of multiple lineages from the continental centre to the more mesic fringes as Australia became progressively more arid, with subsequent extinction in the centre, and also (2) origination of ancestral lineages in southwestern Australia (SWA) for species-rich clades. The SWA biodiversity hotspot is a major diversification centre and the most common source area of dispersals, with multiple lineages originating in SWA and subsequently spreading to the adjacent arid Eremaean region. 

CONCLUSIONS: Our results suggest major extinction as a result of cooling and drying of the Australian continent in the Eocene–Miocene shaped the present-day biogeography of Calytrix. We hypothesise that this peripheral vicariance pattern, which is similar to the African Rand flora, may explain the disjunctions of many other Australian plant groups. Further studies with densely sampled phylogenies are required to test this hypothesis.

Read me file contains description of the folders and associated files. The submission includes:

BEAST_files:
Alignments of gene regions sourced from GenBank (outgroups) as well as newly sequenced NGS data from this study. This folder also includes the xml files with fossil calibrations and final trees from BEAST analyses found in the figures of the main manuscript as well as supplementary figures (as tree files).

BioGeoBEARS_files:
Input files (tree, biogeographic states for each taxa, and time scale scenarios) for the BioGeoBEAR runs.

ASTRAL_files:
Individual nuclear gene trees (RAxML) and species tree output from ASTRAL.

IQTree_files:
alignment and partition files and output tree from IQTree for nuclear dataset (nr-CON).

plastid-RAXML_files
Alignments of plastid gene regions and output tree file with bootstrap support.