Assembly of Australia's Alpine Seed Plant Flora

ABSTRACT To characterise the assembly of Australia's distinctive native alpine seed plant flora. Past events when species were sequestered into the alpine habitat from warmer climates and/or distant regions were identified using published phylogenies and distribution information. I identified that 327 sequestration events were required to create 534 native Australian alpine species in 62 families. Of these events, 76% resulted in only one species, 13% were followed by minor radiations (14 species), and 10% were ambiguous (143 species) and may have involved multiple sequestrations. The latter and convergent evolution mean that the count of 327 events may be an underestimate. The alpine flora is dominated by groups that arrived in Australia long after the break‐up of Gondwana (at least 63% of the species and 54% of the sequestration events), and mostly appear to have reached Australia by trans‐oceanic dispersal. However, most of these recent events involved the intermediate step of occupying non‐alpine habitats prior to colonising alpine habitats (at least 46% of these events and 53% of the species). Most of these latter groups mostly came from Africa, but Eurasia and the Americas also contributed. Groups that arrived directly from other regions mostly appear to have come from New Zealand. Alpine Tasmania, especially western Tasmania, has more old Australian groups, including remarkable palaeoendemics, and more woody species than alpine mainland Australia. Australia's alpine flora is a dynamic system, largely assembled by relatively recent sequestration of a diverse range of species, with a modest amount of subsequent speciation within the biome. The flora was predominantly (at least 68% of the species) assembled from local sources, but there was also significant direct sequestration from floras of other landmasses, especially New Zealand. I discuss possible factors involved in the creation of these patterns as well as uncertainties.