Fichant T, Ledent A, Collart F, Vanderpoorten A
Institute of Botany, University of Liège, Liège, Belgium.
Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
Front Plant Sci. 2023 Oct 30;14:1289240. doi: 10.3389/fpls.2023.1289240. eCollection 2023.
The dramatic fluctuations of climate conditions since the late Tertiary era have resulted in major species range shifts. These movements were conditioned by geographic barriers and species dispersal capacities. In land plants, gene flow occurs through the movement of male gametes (sperm cells, pollen grains), which carry nDNA, and diaspores (spores, seeds), which carry both cpDNA and nDNA, making them an ideal model to compare the imprints of past climate change on the spatial genetic structures of different genomic compartments. Based on a meta-analysis of cpDNA and nDNA sequence data in western Europe, we test the hypotheses that nDNA genetic structures are similar in bryophytes and spermatophytes due to the similar size of spores and pollen grains, whereas genetic structures derived from the analysis of cpDNA are significantly stronger in spermatophytes than in bryophytes due to the substantially larger size of seeds as compared to spores.
Sequence data at 1-4 loci were retrieved for 11 bryophyte and 17 spermatophyte species across their entire European range. Genetic structures between and within southern and northern populations were analyzed through F and N statistics and Mantel tests.
Gst and Nst between southern and northern Europe derived from cpDNA were significantly higher, and the proportion of significant tests was higher in spermatophytes than in bryophytes. This suggests that in the latter, migrations across mountain ranges were sufficient to maintain a homogenous allelic structure across Europe, evidencing the minor role played by mountain ranges in bryophyte migrations. With nDNA, patterns of genetic structure did not significantly differ between bryophytes and spermatophytes, in line with the hypothesis that spores and pollen grains exhibit similar dispersal capacities due to their size similarity. Stronger levels of genetic differentiation between southern and northern Europe, and within southern Europe, in spermatophytes than in bryophytes, caused by higher long-distance dispersal capacities of spores as compared to seeds, may account for the strikingly higher levels of endemism in spermatophytes than in bryophytes in the Mediterranean biodiversity hotspot.
自第三纪晚期以来，气候条件的剧烈波动导致了主要物种分布范围的变化。这些迁移受到地理障碍和物种扩散能力的制约。在陆地植物中，基因流动通过携带核DNA的雄配子（精子细胞、花粉粒）以及携带叶绿体DNA和核DNA的传播体（孢子、种子）的移动而发生，这使得它们成为比较过去气候变化对不同基因组区域空间遗传结构影响的理想模型。基于对西欧叶绿体DNA和核DNA序列数据的荟萃分析，我们检验了以下假设：由于孢子和花粉粒大小相似，苔藓植物和种子植物的核DNA遗传结构相似；而由于种子比孢子大得多，但叶绿体DNA分析得出的遗传结构在种子植物中比在苔藓植物中明显更强。
检索了11种苔藓植物和17种种子植物在整个欧洲分布范围内1至4个位点的序列数据。通过F和N统计以及Mantel检验分析了南部和北部种群之间以及种群内部的遗传结构。
来自叶绿体DNA的南北欧之间的Gst和Nst显著更高，种子植物中显著检验的比例高于苔藓植物。这表明，在苔藓植物中，跨山脉的迁移足以在欧洲维持均匀的等位基因结构，证明了山脉在苔藓植物迁移中所起的作用较小。对于核DNA，苔藓植物和种子植物之间的遗传结构模式没有显著差异，这与孢子和花粉粒由于大小相似而具有相似扩散能力的假设一致。与种子相比，孢子更高的远距离扩散能力导致种子植物在南北欧之间以及南欧内部的遗传分化程度比苔藓植物更强，这可能解释了在地中海生物多样性热点地区种子植物的特有性水平明显高于苔藓植物的原因。
