State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China.
Institute of Molecular Plant Sciences, University of Edinburgh, Edinburgh, UK.
Mol Ecol. 2022 Mar;31(5):1543-1561. doi: 10.1111/mec.16325. Epub 2021 Dec 30.
Global climate changes during the Miocene may have created ample opportunities for hybridization between members of tropical and subtropical biomes at the boundary between these zones. Yet, very few studies have explored this possibility. The Yunnan-Guizhou Plateau (YGP) in Southwest China is a biodiversity hotspot for vascular plants, located in a transitional area between the floristic regions of tropical Southeast Asia and subtropical East Asia. The genus Eriobotrya (Rosaceae) comprises both tropical and subtropical taxa, with 12 species recorded in the YGP, making it a suitable basis for testing the hypothesis of between-biome hybridization. Therefore, we surveyed the evolutionary history of Eriobotrya by examining three chloroplast regions and five nuclear genes for 817 individuals (47 populations) of 23 Eriobotrya species (including 19 populations of 12 species in the YGP), plus genome re-sequencing of 33 representative samples. We concluded that: (1) phylogenetic positions for 16 species exhibited strong cytonuclear conflicts, most probably due to ancient hybridization; (2) the YGP is a hotspot for hybridization, with 11 species showing clear evidence of chloroplast capture; and (3) Eriobotrya probably originated in tropical Asia during the Eocene. From the Miocene onwards, the intensification of the Eastern Asia monsoon and global cooling may have shifted the tropical-subtropical boundary and caused secondary contact between species, thus providing ample opportunity for hybridization and diversification of Eriobotrya, especially in the YGP. Our study highlights the significant role that paleoclimate changes probably played in driving hybridization and generating rich species diversity in climate transition zones.
中新世的全球气候变化可能为热带和亚热带生物群落成员在这些地带的边界之间的杂交提供了充足的机会。然而，很少有研究探索这种可能性。中国西南部的云贵高原（YGP）是维管植物的生物多样性热点地区，位于热带东南亚和亚热带东亚植物区系之间的过渡区。枇杷属（蔷薇科）包括热带和亚热带类群，在 YGP 记录有 12 个种，这使其成为检验跨生物群落杂交假说的合适基础。因此，我们通过检查三个叶绿体区域和五个核基因对来自 23 种枇杷属（包括 YGP 中的 12 种的 47 个种群）的 817 个个体（包括 YGP 中的 19 个种群的 12 种）以及 33 个代表样本的基因组重测序来研究枇杷属的进化历史。我们得出结论：（1）16 个种的系统发育位置表现出强烈的核质冲突，很可能是由于古老的杂交；（2）YGP 是杂交的热点地区，有 11 个种显示出明显的叶绿体捕获证据；（3）枇杷属可能起源于始新世的热带亚洲。从中新世开始，东亚季风的加强和全球变冷可能使热带-亚热带边界发生转移，并导致物种之间的二次接触，从而为枇杷属的杂交和多样化提供了充足的机会，尤其是在 YGP。我们的研究强调了古气候变化可能在驱动杂交和产生气候过渡带丰富物种多样性方面发挥的重要作用。
