Department of Plant Biology and Ecology, University of Seville, Seville, Spain.
Department of Molecular Biology and Biochemical Engineering, Universidad Pablo de Olavide, Seville, Spain.
Plant Biol (Stuttg). 2018 Jan;20 Suppl 1:166-175. doi: 10.1111/plb.12563. Epub 2017 Apr 3.
The Mediterranean Basin region, home to 25,000 plant species, is included in the worldwide list of hotspots of biodiversity. Despite the indisputably important role of chromosome transitions in plant evolution and diversification, no reference study to date has dealt with the possible relationship between chromosome evolution and lineage diversification in the Mediterranean Basin. Here we study patterns of diversification, patterns of chromosome number transition (either polyploidy or dysploidy) and the relationship between the two for 14 Mediterranean Basin angiosperm lineages using previously published phylogenies. We found a mixed pattern, with half of the lineages displaying a change in chromosome transition rates after the onset of the Mediterranean climate (six increases, one decrease) and the other half (six) experiencing constant rates of chromosome transitions through time. We have also found a heterogeneous pattern regarding diversification rates, with lineages exhibiting moderate (five phylogenies) or low (six) initial diversification rates that either increased (six) or declined (five) through time. Our results reveal no clear link between diversification rates and chromosome number transition rates. By promoting the formation of new habitats and driving the extinction of many species, the Mediterranean onset and the posterior Quaternary climatic oscillations could have been key for the establishment of new chromosomal variants in some plant phylogenies but not in others. While the biodiversity of the Mediterranean Basin may be partly influenced by the chromosomal diversity of its lineages, this study concludes that lineage diversification in the region is largely decoupled from karyotypic evolution.
地中海盆地地区拥有 25000 种植物物种，被列入了全球生物多样性热点地区名单。尽管染色体转变在植物进化和多样化中无疑起着重要作用，但迄今为止，没有任何参考研究涉及地中海盆地中染色体进化与谱系多样化之间的可能关系。在这里，我们使用先前发表的系统发育树研究了 14 个地中海盆地被子植物谱系的多样化模式、染色体数转变（多倍体或非整倍体）模式以及两者之间的关系。我们发现了一种混合模式，其中一半的谱系在地中海气候开始后显示出染色体转变率的变化（六次增加，一次减少），另一半（六次）经历了染色体转变率的恒定。我们还发现了关于多样化率的不均匀模式，具有中等（五个系统发育树）或低（六个）初始多样化率的谱系，其多样化率随着时间的推移要么增加（六个）要么减少（五个）。我们的结果表明，多样化率与染色体数转变率之间没有明显联系。地中海的出现和随后的第四纪气候波动通过形成新的栖息地并推动许多物种的灭绝，可能是某些植物谱系中新的染色体变体形成的关键，但不是其他谱系的关键。虽然地中海盆地的生物多样性可能部分受到其谱系的染色体多样性的影响，但本研究得出的结论是，该地区的谱系多样化与核型进化在很大程度上是脱钩的。
