A first perspective on evolution and diversification of Australasian Teucrium (Lamiaceae) and improved insight to selecting contemporary genomic techniques.

Trevor C. Wilson (Botanic Gardens of Sydney); Elizabeth James (Royal Botanic Gardens Victoria); Russell Barrett (Botanic Gardens of Sydney); Marlien vanderMerwe (Botanic Gardens of Sydney); Saphira Bloom-Quinn (Botanic Gardens of Sydney).

Teucrium L. (Lamiaceae) is a cosmopolitan genus with a Mediterranean centre of diversity. We tested recently-made generic synonymies and species concepts using phylogenomic analysis of nuclear genes sequenced via targeted enrichment (Angiosperms-353 baits) for replicates of all (27) Australasian species and phrase names. We show that the diversity of Teucrium across Australasia constitutes two distantly related clades. The most speciose clade is a component of the ‘core Teucrium clade’ and has diversified across Australia and into New Zealand whereas the second consists of three eastern Australian species belonging to the ‘Polium clade’. The former clade consists of basally-derived branches of western Australian species, hinting at a southwestern origin. It also exhibits two independent radiations into the Australian arid inland, one coinciding with a distinctive shift in pollination strategy and seed dispersal. Overall, analysis of target-bait capture data produced a tree with high support for most species clades and was able to unequivocally place most ‘unknowns’. We identify advantages and limitations of using the technique for better-equiping future systematic studies through examining its ability to resolve Teucrium species complexes (e.g. T. corymbosum) and through comparative assessment with SNP-based genomic scans.