Nge Francis J, Skeels Alexander
National Herbarium of New South Wales, Botanic Gardens of Sydney, Locked Bag 6002, Mount Annan, NSW, 2567, Australia.
School of Biological Sciences, Faculty of Science, The University of Adelaide, Adelaide, SA, 5005, Australia.
New Phytol. 2025 Jun 30. doi: 10.1111/nph.70330.
The macroevolutionary drivers for disparities in plant species richness across Australia are understudied, hindered by lack of densely sampled comparative phylogenetic data. Here, we address this gap by analysing plant diversification dynamics and quantifying macroevolutionary trajectories of 22 plant clades (4289 species in 14 families) across two Australian regions. We show the southwest Australian (SWA) floristic region differs from southeastern Australia (SEA) in having relatively low speciation and extinction rates, fewer recent rapid radiations, declining speciation rates, relatively high rates of sympatric speciation indicative of greater niche space saturation, and an absence of mass extinction events since the Eocene. We show that low diversification rates in SWA can be attributed to the early diversification and old age of its flora. By contrast, the SEA extant flora largely diversified after the Eocene-Oligocene boundary extinction event. The paucity of diversification rate shifts across the two floras is likely linked to the lack of extreme environmental pulse events on the geologically stable Australian continent. Our results uncover the dynamics, which have shaped the SWA region as a current centre of hyperdiversity in a continental and global context and suggests an alternate pathway to diversity, not found in other biodiversity hotspots.
澳大利亚植物物种丰富度差异的宏观进化驱动因素尚未得到充分研究，这受到缺乏密集采样的比较系统发育数据的阻碍。在这里，我们通过分析植物多样化动态并量化澳大利亚两个地区22个植物分支（14个科中的4289种）的宏观进化轨迹来填补这一空白。我们发现，澳大利亚西南部（SWA）植物区系与澳大利亚东南部（SEA）不同，其物种形成和灭绝率相对较低，近期快速辐射较少，物种形成率下降，同域物种形成率相对较高，表明生态位空间饱和度更高，并且自始新世以来没有大规模灭绝事件。我们表明，SWA地区多样化率低可归因于其植物区系的早期多样化和古老性。相比之下，SEA现存植物区系在始新世 - 渐新世边界灭绝事件之后大多实现了多样化。两个植物区系中多样化率变化的缺乏可能与地质稳定的澳大利亚大陆上缺乏极端环境脉冲事件有关。我们的结果揭示了在大陆和全球背景下塑造SWA地区成为当前超级多样性中心的动态过程，并提出了一条在其他生物多样性热点地区未发现的多样化替代途径。
