Karbstein Kevin, Tomasello Salvatore, Hodač Ladislav, Lorberg Ellen, Daubert Mareike, Hörandl Elvira
Department of Systematics, Biodiversity and Evolution of Plants (with Herbarium), Albrecht-von-Haller Institute for Plant Sciences, University of Göttingen, Göttingen, Germany.
Georg-August University School of Science (GAUSS), University of Göttingen, Göttingen, Germany.
Mol Ecol. 2021 Jun;30(11):2659-2675. doi: 10.1111/mec.15919. Epub 2021 May 7.
Geographical parthenogenesis (GP) describes the phenomenon that apomicts tend to have larger distribution areas and/or occur at higher altitudes or latitudes compared to sexual relatives. However, the complex effects of genome-wide heterozygosity, ploidy, reproduction mode (sexual vs. apomictic), and environment shaping GP of plants are still not well understood. We ascertained ploidy and reproduction mode by flow cytometry of 221 populations, and added genomic RADseq data (maximum 33,165 loci) of 80 taxa of the Ranunculus auricomus polyploid plant complex in temperate Europe. We observed 7% mainly diploid sexual, 28% facultative apomictic (mean sexuality 7.1%), and 65% obligate apomictic populations. Sexuals occupied a more southern, smaller distribution area, whereas apomicts expanded their range to higher latitudes. Within the complex, we detected three main genetic clusters and highly reticulate relationships. A genetically-informed path analysis using GLMMs revealed several significant relationships. Sexuality of populations (percent of sexual seeds) was higher in diploids compared to polyploids, associated with more petals, and similar between forests and open habitats. In contrast to other apomictic plant complexes, sexuality was mainly positively correlated to solar radiation and isothermality, which fits the southern distribution. We found up to three times higher heterozygosity in polyploids compared to diploids, and generally more heterozygous individuals in forests compared with open habitats. Interestingly, we revealed a previously unknown positive association between heterozygosity and temperature seasonality, suggesting a higher resistance of polyploids to more extreme climatic conditions. We provide empirical evidence for intrinsic and extrinsic factors shaping the GP pattern in a polyploid plant complex.
地理孤雌生殖（GP）描述了这样一种现象：与有性生殖的近缘种相比，无融合生殖的物种往往具有更大的分布区域，和/或出现在更高的海拔或纬度地区。然而，全基因组杂合性、倍性、繁殖方式（有性生殖与无融合生殖）以及环境对植物地理孤雌生殖的复杂影响仍未得到充分理解。我们通过对221个种群进行流式细胞术确定了倍性和繁殖方式，并补充了欧洲温带毛茛多倍体植物复合体80个分类群的基因组RADseq数据（最多33,165个位点）。我们观察到7%主要是二倍体有性生殖种群，28%是兼性无融合生殖种群（平均有性生殖率为7.1%），65%是专性无融合生殖种群。有性生殖种群分布在更偏南、更小的区域，而无融合生殖种群的分布范围扩展到了更高的纬度。在这个复合体中，我们检测到三个主要的遗传簇和高度网状的关系。使用广义线性混合模型（GLMMs）进行的遗传信息路径分析揭示了几个显著的关系。与多倍体相比，二倍体种群的有性生殖率（有性种子的百分比）更高，与更多花瓣相关，并且在森林和开阔生境中相似。与其他无融合生殖植物复合体不同，有性生殖率主要与太阳辐射和等温性呈正相关，这与南方的分布情况相符。我们发现多倍体的杂合性比二倍体高多达三倍，并且与开阔生境相比，森林中通常有更多杂合个体。有趣的是，我们揭示了杂合性与温度季节性之间以前未知的正相关关系，这表明多倍体对更极端气候条件具有更高的抗性。我们为塑造多倍体植物复合体地理孤雌生殖模式的内在和外在因素提供了实证证据。
