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Nge, Francis [1], Waycott, Michelle [1], Biffin, Ed [1], Thiele, Kevin [2].

Diversification dynamics and evolution of old biodiversity hotspots – the Australian temperate flora has no global analogue.

Spectacular radiations across many biodiversity hotspots and other species-rich regions have been linked to recent environmental changes such as mountain uplifts or shifts in climate regimes. This suggests that abrupt pulse events are important drivers for the evolution and diversification of global biodiversity hotspots. Here we present a detailed assessment of diversification dynamics in the Australian temperate flora, an excellent model for addressing the role of abrupt environmental change on species radiations given the relative climatic stability and lack of recent tectonic activity across the continent, in contrast to other biodiverse regions. We compared diversification rates in the southwestern Australian biodiversity hotspot (SWA) and southeastern Australia (SEA) with other global species-rich regions. We applied a series of diversification models with a focus on region-specific diversification dynamics across 22 different plant phylogenies (5716 species). We show that SWA has the lowest diversification rate of any biodiversity hotspot. SEA has a slightly higher diversification rate due to higher speciation rates after the Eocene-Oligocene boundary extinction event, but is still low relative to other biodiverse regions. The SWA flora is characterised by low and declining speciation rates, steady accumulation of species, lack of recent radiation shifts, density-dependent diversification slowdowns indicative of niche-space saturation, and absence of mass extinction events since the Cretaceous. The SWA flora likely has no comparable analogue on Earth. Its unusual features are attributed to the old age and assembly of its flora, linked to a gradual accumulation of lineages. The relatively old age of the SWA flora, and the Australian flora more generally, is attributable to a lack of extreme environmental pulse events on the subdued and tectonically stable Australian landscape. Further evolutionary studies on the Australia biota and on other older biodiverse regions focusing on long timescales may yield important insights into evolutionary drivers that may be fundamentally different to other regions of the planet. The evolution and biogeographic patterns of several case study groups relating to these drivers are also discussed.  

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1 - the University of Adelaide, School of Biological Sciences, North Terrace, Adelaide, South Australia, 5000, Australia
2 - the University of Western Australia, School of Biological Sciences, 35 Stirling Highway, Crawley, Perth, Western Australia, 6009, Australia

Australian flora
biodiversity hotspot
tropical rainforests.

Presentation Type: Oral Paper
Session: MACROII, Macroevolution II
Location: Virtual/Virtual
Date: Thursday, July 22nd, 2021
Time: 12:30 PM(EDT)
Number: MACROII001
Abstract ID:338
Candidate for Awards:None

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