Isolation by environment (IBE) is a widespread phenomenon in nature. It is commonly expected that the degree of difference among environments is proportional to the level of divergence between populations in their respective environments. It is therefore assumed that a species' genetic diversity displays a pattern of IBE in the presence of a strong environmental cline if gene flow does not mitigate isolation. We tested this common assumption by analysing the genetic diversity and demographic history of Pisum fulvum, which inhabits contrasting habitats in the southern Levant and is expected to display only minor migration rates between populations, making it an ideal test case. Ecogeographical and subpopulation structure were analysed and compared. The correlation of genetic with environmental distances was calculated to test the effect of isolation by distance and IBE and detect the main drivers of these effects. Historical effective population size was estimated using stairway plot. Limited overlap of ecogeographical and genetic clustering was observed, and correlation between genetic and environmental distances was statistically significant but small. We detected a sharp decline of effective population size during the last glacial period. The low degree of IBE may be the result of genetic drift due to a past bottleneck. Our findings contradict the expectation that strong environmental clines cause IBE in the absence of extensive gene flow.

中文翻译：

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尽管野生豌豆有大量环境变化，但适应适应性有限。

环境隔离（IBE）是自然界中普遍存在的现象。通常期望，环境之间的差异程度与各自环境中人口之间的差异程度成正比。因此，假设如果基因流不能减轻隔离的话，一个物种的遗传多样性会在环境强势存在的情况下表现出IBE模式。我们通过分析黄豌豆的遗传多样性和人口历史资料，测试了这个普遍的假设，它居住在黎凡特南部不同的栖息地，预计在种群之间的迁移率很小，这使其成为理想的测试用例。分析和比较了生态地理和亚种群结构。计算遗传与环境距离的相关性，以测试通过距离和IBE隔离的效果，并检测这些效果的主要驱动因素。使用楼梯图估算历史有效人口规模。观察到生态地理和遗传聚类的重叠有限，遗传距离与环境距离之间的相关性在统计上显着，但很小。在上一个冰川期，我们发现有效人口规模急剧下降。IBE的低水平可能是由于过去的瓶颈导致的基因漂移的结果。