The classification and typification of all Australian ferns and lycophytes is updated to reflect the Pteridophyte Phylogeny Group I classification and the International Code of Nomenclature for algae, fungi, and plants, presenting 8 new nomenclatural combinations as well as 85 lectotypifications. The Australian fern and lycophyte flora comprises 2 classes, 14 orders, 32 families, 134 genera and 528 species and subspecies with the addition of 8 newly recorded and 6 newly recognised species since the publication of the Flora of Australia fern volume in 1998. Overall, 208 species are endemic to Australia, with Queensland having the highest species diversity and endemism by state or territory, and Lord Howe Island having the highest concentration of species and endemics per unit area. The Australian fern and lycophyte flora shows diverse links with Africa, Asia and Oceania, with the largest overlaps being shared with Asia and Oceania. More species are endemic to Australia+Oceania than to Australia+Asia. Contrasting with the classification presented in the Flora of Australia, no genera of ferns and lycophytes are now considered to be wholly endemic to Australia.

The genus Vachellia Wight & Arn. has a pantropical distribution, with species being distributed through Africa, the Americas, Asia and Australia. The relationships among the lineages from Africa and America are well understood, but the phylogenetic placement and evolutionary origins of the Australian species of Vachellia are not known. We, therefore, sequenced four plastid genes from representatives of each of the nine Australian species of Vachellia, and used Bayesian inference to assess the phylogenetic placement of these lineages, and a relaxed molecular clock to assess the timing of diversification. The Australian species of Vachellia form a well-supported monophyletic clade, with molecular-dating analysis suggesting a single dispersal into Australia 6.5 million years ago (95% range 13.9–2.7 million years ago). Diversification of the Australian clade commenced more recently, c. 3.1 million years ago (95% range 9.2–1.2 million years ago), perhaps driven by the increased aridification of Australia at this time. The closest relatives to the Australian Vachellia were not from the Malesian bioregion, suggesting either a long-distance dispersal from Africa, or two separate migrations through Asia. These results not only improve our understanding of the biogeography of Vachellia species, but also have significant implications for the biological control of invasive Vachellia species in Australia.

Speciation is a central process in evolutionary biology and is responsible for the diversity of life on Earth. Although there has been much progress in evolutionary research over the past 150 years, understanding the many facets of speciation remains a challenge. In this synthesis, I focus on the use of an interdisciplinary approach to examine speciation and species delimitation in a group of closely related eucalypts called the green ashes (Eucalyptus subgenus Eucalyptus section Eucalyptus). The green ashes comprise tall trees on fertile soils (e.g. the tallest angiosperm in the world, E. regnans), as well as medium trees and mallees on low-nutrient soils. Previous phylogenetic and population-genetics analyses based on genome-wide scans showed that species boundaries in the green ashes are not always consistent with classifications based on morphology and there was evidence of gene flow across lineages. Genomic analyses also suggested that the green ashes were at varying stages of speciation, with some species being highly genetically differentiated, whereas others were at earlier stages on the speciation continuum. A previous common garden study showed that inter-specific differences in seedling traits were significant, with traits such as leaf width being highly plastic across resource treatments for most species. Overall, this synthesis demonstrated that an interdisciplinary approach incorporating phylogenomics, population genomics and a common garden experiment can provide insights into speciation and species delimitation in the green ash eucalypts. Such an approach may be useful in understanding the evolutionary history of other closely related species in Eucalyptus, as well as other groups of organisms.