在气候梯度上，土壤专性种的功能性状高度分化，但表型可塑性相似。
High differentiation in functional traits but similar phenotypic plasticity in populations of a soil specialist along a climatic gradient.
机构信息
Área de Biodiversidad y Conservación, Universidad Rey Juan Carlos. C/Tulipán s/n 28933, Móstoles, Spain.
出版信息
Ann Bot. 2020 May 13;125(6):969-980. doi: 10.1093/aob/mcaa020.
BACKGROUND AND AIMS
Plants experiencing contrasting environmental conditions may accommodate such heterogeneity by expressing phenotypic plasticity, evolving local adaptation or a combination of both. We investigated patterns of genetic differentiation and plasticity in response to drought in populations of the gypsum specialist Lepidium subulatum.
METHODS
We created an outdoor common garden with rain exclusion structures using 60 maternal progenies from four distinct populations that substantially differ in climatic conditions. We characterized fitness, life history and functional plasticity in response to two contrasting treatments that realistically reflect soil moisture variation in gypsum habitats. We also assessed neutral genetic variation and population structure using microsatellite markers.
KEY RESULTS
In response to water stress, plants from all populations flowered earlier, increased allocation to root tissues and advanced leaf senescence, consistent with a drought escape strategy. Remarkably, these probably adaptive responses were common to all populations, as shown by the lack of population × environment interaction for almost all functional traits. This generally common pattern of response was consistent with substantial neutral genetic variation and large differences in population trait means. However, such population-level trait variation was not related to climatic conditions at the sites of origin.
CONCLUSIONS
Our results show that, rather than ecotypes specialized to local climatic conditions, these populations are composed of highly plastic, general-purpose genotypes in relation to climatic heterogeneity. The strikingly similar patterns of plasticity among populations, despite substantial site of origin differences in climate, suggest past selection on a common norm of reaction due to similarly high levels of variation within sites. It is thus likely that plasticity will have a prevalent role in the response of this soil specialist to further environmental change.
背景与目的
经历环境条件差异的植物可能通过表现出表型可塑性、进化出局部适应性或两者的组合来适应这种异质性。我们研究了在四个气候条件差异很大的石膏专性种 Lepidium subulatum 种群中，对干旱的遗传分化和可塑性模式。
方法
我们使用来自四个不同种群的 60 个母本后代创建了一个带有雨水排除结构的户外通用花园，这些种群在气候条件上有很大的差异。我们描述了在两种对比处理下的适应性、生活史和功能可塑性，这两种处理真实地反映了石膏栖息地土壤水分的变化。我们还使用微卫星标记评估了中性遗传变异和种群结构。
主要结果
在水分胁迫下，来自所有种群的植物都更早地开花，将分配给根组织的比例增加，并提前进入叶片衰老，这与干旱逃避策略一致。值得注意的是，这些可能的适应性反应在所有种群中都是常见的，因为几乎所有功能性状都没有种群与环境的相互作用。这种普遍的共同响应模式与大量的中性遗传变异和种群性状均值的巨大差异一致。然而，这种种群水平的性状变异与起源地的气候条件无关。
结论
我们的结果表明，这些种群不是专门适应当地气候条件的生态型，而是与气候异质性相关的高度可塑性、通用基因型。尽管在起源地气候上存在显著差异，但种群之间的可塑性模式非常相似，这表明过去在相同的地点选择了一个共同的反应规范，因为在这些地点内存在着相似的高水平变异。因此，可塑性很可能在这种土壤专家对进一步环境变化的反应中发挥主导作用。
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