Premise Different cytotypes of a species may differ in their morphology, phenology, physiology, and their tolerance of extreme environments. We studied the ecological niches of two subspecies of Saxifraga rosacea with different ploidy levels: the hexaploid Central European endemic subspecies sponhemica and the more widely distributed octoploid subspecies rosacea. Methods For both cytotypes, we recorded local environmental conditions and mean plant trait values in populations across their areas of distribution, analyzed their distributions by niche modeling, studied their performance at two transplant sites with contrasting conditions, and experimentally tested their cold resistance. Results Mean annual temperature was higher in hexaploid than in octoploid populations and experiments indicated that frost tolerance of the hexaploid is lower than that of the octoploid. Reproduction of octoploids from Central Europe was higher than that of hexaploids at a transplant site in subarctic Iceland, whereas the opposite was true in temperate Luxembourg, indicating adaptation of the octoploids to colder conditions. Temperature variables were also most important in niche models predicting the distribution of the two cytotypes. Genetic differences in survival among populations were larger for the octoploids than for the hexaploids in both field gardens, suggesting that greater genetic variability may contribute to the octoploid's larger distributional range. Conclusions Our results support the hypotheses that different cytotypes may have different niches leading to spatial segregation, and that higher ploidy levels can result in a broader ecological niche and greater tolerance of more extreme conditions.

中文翻译：

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虎耳草两种多倍体细胞型的生态位差异

前提 一个物种的不同细胞类型可能在形态、物候、生理和对极端环境的耐受性方面有所不同。我们研究了具有不同倍性水平的虎耳草两个亚种的生态位：六倍体中欧地方性亚种 sponhemica 和分布更广泛的八倍体亚种酒渣鼻。方法对于两种细胞类型，我们记录了其分布区域内种群的局部环境条件和平均植物性状值，通过生态位模型分析了它们的分布，研究了它们在具有对比条件的两个移植地点的性能，并通过实验测试了它们的抗寒性。结果六倍体种群的年平均气温高于八倍体种群，实验表明六倍体的抗冻性低于八倍体。在亚北极冰岛的移植地点，来自中欧的八倍体的繁殖率高于六倍体，而温带的卢森堡则相反，表明八倍体适应了较冷的条件。温度变量在预测两种细胞类型分布的生态位模型中也是最重要的。在两个田间花园中，八倍体的种群生存遗传差异大于六倍体，这表明更大的遗传变异可能导致八倍体的分布范围更大。