Angiosperms are believed to have emerged initially in the tropics and expanded their distribution range poleward through diverse mechanisms, for example polyploidization‐driven cold tolerance evolution. Reversed expansion from temperate to pan‐tropic climates through a polyploidization‐driven shift in heat tolerance remains largely unknown. Here, we found autopolyploidy in relation to the global expansion of Solidago canadensis from its temperate‐climate native range in North American to hot‐summer climate in an introduced range. Our cytogeographical study of 2,062 accessions from 471 locations worldwide demonstrates that ploidy levels correlate negatively with latitude and positively with average temperature. An isotherm‐dependent shift of the climate niches at the threshold of 20°–24°C between geo‐cytotypes can be attributed mainly to autopolyploidy‐driven differentiation of heat tolerance; only polyploids and not diploids are able to complete sexual reproduction, germinate, and grow in the hot‐summer climate of low latitudes. Ploidy‐dependent fertility appears to play a key role in the hot‐summer introduced range in the northern hemisphere through both pre‐adaptation and rapid post‐introduction adaptive evolution of delayed flowering and improved heat tolerance during embryo development. The MaxEnt model predicts continued expansion of this plant species under global change. These results provide new insights into the mechanisms governing autopolyploidy‐driven backward range expansion of plant species from temperate origins.

中文翻译：

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在全球变化下，由多倍体驱动的温带起源植物向泛热带范围的扩展

据信被子植物最初出现在热带地区，并通过多种机制，例如由多倍体化驱动的耐寒性进化，极快地扩大了它们的分布范围。通过多倍体化驱动的耐热性转变，从温带气候向泛热带气候的逆向膨胀仍是未知之数。在这里，我们发现了与加拿大一枝黄花全球扩张有关的同源多倍体从北美的温带气候原生范围到引入范围的炎热夏季气候。我们对来自全球471个地点的2,062个种质的细胞地理研究表明，倍性水平与纬度呈负相关，与平均温度呈正相关。地域细胞型之间在20°–24°C阈值之间气候ches的等温线变化主要归因于多倍体驱动的耐热性差异。在低纬度的炎热夏季，只有多倍体而不是二倍体能够完成有性繁殖，发芽和生长。倍性依赖的育性在北半球炎热的夏季引进范围中似乎起着关键作用，通过适应性适应和引入后快速适应性进化来延迟开花并改善胚胎发育期间的耐热性。MaxEnt模型预测在全球变化下该植物物种的持续扩张。这些结果为从温带起源的植物多倍体驱动的向后范围扩展的调控机制提供了新见解。