Natural populations of plants may express plastic response, evolve local adaptation, or combine both mechanisms to enhance their genetic variation. Here, 79 lines from Tunisian Brachypodium hybridum populations were cultivated in two contrasting phosphorus (P) availability levels, and their genetic variation was investigated using forage quality traits to identify the mechanisms governing their genetic variation. Results revealed large variation among populations for most traits and separation between coastal and inland populations in both P levels. All traits revealed high heritability, and the response of most traits to P deficiency was influenced by the population effect which accounted 52.38% of the variation, indicating strong population differentiation. Although significant for most traits, only 18.13% of variation was attributed to P treatment, suggesting little plastic response to P deficiency. However, the lack of population × treatment effect for most traits suggested a common plastic response in populations. Moreover, 56.99% of variation was attributed to environmental factors with distance to coastline, precipitation seasonality, and annual precipitation being the major factors, suggesting that the strong population differentiation reflects local adaptation to specific environments. Contrary to coastal populations characterized by high levels of fiber-related traits, the inland ones displayed high values of most energy-related traits, suggesting that these latter were characterized by higher forage quality. Overall, our results suggested that the effect of local adaptation overrides the effect of phenotypic plasticity regarding the variation of forage quality traits, indicating a broad adaptive genetic differentiation among the populations of B. hybridum in response to P deficiency.

中文翻译：

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突尼斯短柄草种群草料品质性状响应磷缺乏的变化

植物的自然种群可能会表达可塑性反应、进化局部适应性，或将这两种机制结合起来以增强其遗传变异。这里，来自突尼斯Brachypodium hybridum 的79 个品系在两种不同的磷 (P) 可用性水平下培育种群，并使用草料质量性状研究它们的遗传变异，以确定控制其遗传变异的机制。结果表明，在两个 P 水平上，大多数性状种群之间的差异很大，沿海和内陆种群之间存在很大差异。所有性状均表现出高遗传力，大多数性状对缺磷的反应受群体效应的影响，占变异的52.38%，表明群体分化强烈。尽管对大多数性状很重要，但只有 18.13% 的变异归因于磷处理，表明对磷缺乏的可塑性反应很小。然而，大多数性状缺乏群体×治疗效果表明群体中存在共同的可塑性反应。此外，56。99%的变异归因于环境因素，其中距海岸线距离、降水季节性和年降水量是主要因素，表明强烈的人口分化反映了当地对特定环境的适应。与具有高水平纤维相关性状特征的沿海种群相反，内陆种群显示出大多数与能量相关的性状的高值，表明后者具有较高的草料质量。总的来说，我们的结果表明，局部适应的影响超过了表型可塑性对牧草质量性状变异的影响，表明不同种群之间存在广泛的适应性遗传分化。年降水量是主要因素，表明强烈的人口分化反映了当地对特定环境的适应。与具有高水平纤维相关性状特征的沿海种群相反，内陆种群显示出大多数与能量相关的性状的高值，表明后者具有较高的草料质量。总的来说，我们的结果表明，局部适应的影响超过了表型可塑性对牧草质量性状变异的影响，表明不同种群之间存在广泛的适应性遗传分化。年降水量是主要因素，表明强烈的人口分化反映了当地对特定环境的适应。与具有高水平纤维相关性状特征的沿海种群相反，内陆种群显示出大多数与能量相关的性状的高值，表明后者具有较高的草料质量。总的来说，我们的结果表明，局部适应的影响超过了表型可塑性对牧草质量性状变异的影响，表明不同种群之间存在广泛的适应性遗传分化。内陆的大多数与能量相关的性状显示出高值，表明后者的特点是较高的草料质量。总的来说，我们的结果表明，局部适应的影响超过了表型可塑性对牧草质量性状变异的影响，表明不同种群之间存在广泛的适应性遗传分化。内陆的大多数与能量相关的性状显示出高值，表明后者的特点是较高的草料质量。总的来说，我们的结果表明，局部适应的影响超过了表型可塑性对牧草质量性状变异的影响，表明不同种群之间存在广泛的适应性遗传分化。B. hybridum响应 P 缺乏。