The monumental work of Olov Hedberg provided deep insights into the spectacular and fragmented tropical alpine flora of the African sky islands. Here we review recent molecular and niche modelling studies and re-examine Hedberg’s hypotheses and conclusions. Colonisation started when mountain uplift established the harsh diurnal climate with nightly frosts, accelerated throughout the last 5 Myr (Plio-Pleistocene), and resulted in a flora rich in local endemics. Recruitment was dominated by long-distance dispersals (LDDs) from seasonally cold, remote areas, mainly in Eurasia. Colonisation was only rarely followed by substantial diversification. Instead, most of the larger genera and even species colonised the afroalpine habitat multiple times independently. Conspicuous parallel evolution occurred among mountains, e.g., of gigantism in Lobelia and Dendrosenecio and dwarf shrubs in Alchemilla. Although the alpine habitat was ~ 8 times larger and the treeline was ~ 1000 m lower than today during the Last Glacial Maximum, genetic data suggest that the flora was shaped by strong intermountain isolation interrupted by rare LDDs rather than ecological connectivity. The new evidence points to a much younger and more dynamic island scenario than envisioned by Hedberg: the afroalpine flora is unsaturated and fragile, it was repeatedly disrupted by the Pleistocene climate oscillations, and it harbours taxonomic and genetic diversity that is unique but severely depauperated by frequent bottlenecks and cycles of colonisation, extinction, and recolonisation. The level of intrapopulation genetic variation is alarmingly low, and many afroalpine species may be vulnerable to extinction because of climate warming and increasing human impact.

奥洛夫·赫德伯格 (Olov Hedberg) 的巨著让人们对非洲天空岛屿壮观而零散的热带高山植物群有了深入的了解。在这里，我们回顾最近的分子和生态位模型研究，并重新审视赫德伯格的假设和结论。当山脉隆起形成了带有夜间霜冻的恶劣昼夜气候时，殖民活动就开始了，在过去的 5 密尔（上更新世）期间加速了，并产生了丰富的当地特有植物群。招募主要是来自季节性寒冷的偏远地区（主要是欧亚大陆）的长途分散（LDD）。殖民化之后很少出现实质性的多样化。相反，大多数较大的属甚至物种多次独立地在非洲高山栖息地定居。山脉之间发生了明显的平行进化，例如半边莲和Dendrosenecio的巨人症和Alchemilla的矮灌木。尽管在末次盛冰期，高山栖息地比现在大约 8 倍，林线低约 1000 米，但遗传数据表明，植物区系是由罕见的 LDD 中断的强烈山间隔离形成的，而不是生态连通性。新的证据指出了一个比赫德伯格设想的更年轻、更有活力的岛屿情景：非洲高山植物群不饱和且脆弱，它多次受到更新世气候波动的破坏，它拥有独特的分类和遗传多样性，但由于气候变化而严重退化。频繁的瓶颈以及殖民、灭绝和再殖民的循环。种群内遗传变异的水平低得惊人，由于气候变暖和人类影响的增加，许多非洲高山物种可能容易灭绝。