Although seed trait variations and their relationship to the ecological niche have been studied extensively at the species level, they do not necessarily reflect variations at the population level. In this study, we explored the intra-specific variation in relative embryo length, seed mass and germination speed in 40 populations of Daucus carota distributed across Europe and North America. By including information on local climate conditions, we aimed to examine the impact of the geographical origin on various seed functional traits and to detect potential local adaptation. No significant difference was observed in final seed germination for European and North American seeds incubated at 20°C, nor in seed viability. In European populations, relative embryo length significantly increased with increasing seed mass, but no such relation was found in North American populations. Larger relative embryo length at dispersal resulted in increased germination speed in both European and North American populations. Populations in drier areas typically had seeds with larger relative embryo lengths. Precipitation-related climate variables showed a negative relationship with relative embryo length, indicating a reduction in relative embryo length with increased precipitation. No clear relationship between climate and seed mass was observed. We can conclude that seed functional traits of D. carota are adapted to local climate conditions, as a clear gradient was observed in the relative embryo length of D. carota, which was associated with germination speed and climate. This gradient was less pronounced in North America, which can be explained by its relatively recent introduction to the continent.

中文翻译：

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北美和欧洲气候梯度下野生 Daucus carota 相对胚胎长度和发芽的种内变化

尽管种子性状变异及其与生态位的关系已在物种水平上进行了广泛研究，但它们不一定反映种群水平的变异。在这项研究中，我们探讨了分布在欧洲和北美的 40 个 Daucus carota 种群中相对胚胎长度、种子质量和发芽速度的种内变化。通过纳入有关当地气候条件的信息，我们旨在研究地理起源对各种种子功能性状的影响，并检测潜在的局部适应。在 20°C 下孵育的欧洲和北美种子的最终种子发芽率和种子活力均未观察到显著差异。在欧洲种群中，相对胚胎长度随着种子质量的增加而显著增加，但在北美种群中没有发现这种关系。分散时较大的相对胚胎长度导致欧洲和北美种群的发芽速度加快。较干燥地区的种群通常具有相对胚胎长度较大的种子。降水相关气候变量显示与相对胚胎长度呈负相关，表明相对胚胎长度随着降水的增加而减少。没有观察到气候和种子质量之间的明确关系。我们可以得出结论，D. carota 的种子功能性状适应了当地的气候条件，因为在 D. carota 的相对胚胎长度中观察到明显的梯度，这与发芽速度和气候有关。这种梯度在北美不太明显，这可以通过相对较晚地引入北美大陆来解释。