Temperate eastern Australia was identified as key source area for dispersals to other Australasian regions. Extant distributions of Pterostylidinae in other Australasian regions, such as New Zealand and New Caledonia, are of more recent origin, resulting from long-distance dispersals from the Pliocene onwards. Range expansions from the mesic into the arid zone of eastern Australia (Eremaean region) commenced from the early Pleistocene onwards. Long-distance dispersals to southwest Australia commenced from the late Miocene onwards, after the establishment of the Nullarbor Plain, which constitutes a strong edaphic barrier to mesic plants. The subtribe underwent lineage diversification mainly within its ancestral range, in eastern Australia. The rapid climatic oscillations during the Pleistocene may have acted as important driver of speciation in Pterostylidinae. The majority of extant species were inferred to have originated in the Quaternary, from the Pleistocene onwards. Divergence of all major lineages occurred during the Miocene, accompanied by increased aridification and seasonality of the Australian continent, resulting in strong vegetational changes from rainforest to more open sclerophyllous vegetation. Pterostylidinae were inferred to have originated in eastern Australia in the early Oligocene, coinciding with the complete separation of Australia from Antarctica and the onset of the Antarctic Circumpolar Current, which led to profound changes in the world’s climate. Achlydosa was found to not form part of Pterostylidinae and instead merits recognition at subtribal level, as Achlydosinae. Intrageneric relationships in Pterostylis were clarified and monophyly of eight of 10 sections supported. Phylogenetic analysis of 75 plastid genes provided well-resolved and supported phylogenies. Here, we used a phylogenomic approach to infer evolutionary relationships, divergence times and range evolution in Pterostylidinae (Orchidoideae), the second largest subtribe in the Australian orchid flora, comprising the genera Pterostylis and Achlydosa. However, little is known about the assembly and evolution of Australia’s orchid flora.
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