Abstract

Assessing global variation in phenotypic traits and linking that variation to colonization and range expansion is notably rare in invasion biology. Here, we studied variation in seed size in Centaurea solstitialis, a weed with worldwide distribution. Additionally, we explored how seed size variation affects seedling survival of C. solstitialis under favorable precipitation conditions in Anatolia, an ancestral region, and unfavorable precipitation conditions in Argentina, a non-native region. To that end, we conducted seed collections following dispersal pathways of C. solstitialis in ancestral, expanded, and non-native ranges. Locally, collections followed elevation gradients. Also, we performed a greenhouse experiment with C. solstitialis populations varying in seed size and water additions simulating precipitation patterns in Anatolia and Argentina. Seeds from ancestral populations at low elevation were smaller than those from the rest of study populations. Also, seed size in populations at high elevation in the expanded range, the main source of non-native populations, was similar to that in all, but one non-native population, where seeds exhibited further increase. Increments in seed size thus track range expansion in C. solstitialis. Locally, seed size increased with elevation in all three ranges, suggesting convergent responses to that gradient. Seedlings from larger seeds displayed greater survival than those from smaller seeds only under Argentinean conditions. Consequently, populations with large seeds may have been instrumental for colonizing that non-native region. Our findings suggest that ancient and recent dispersal of large-seeded populations contribute to explain the reported global pattern of seed size divergence and worldwide distribution of C. solstitialis.

中文翻译：

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杂草种子大小的增加可追踪全球范围的扩大，并有助于非本地地区的定居

摘要

在入侵生物学中，评估表型性状的整体变异并将其与定植和范围扩展联系起来的情况非常罕见。在这里，我们研究了遍及全球的杂草Centaurea solstitialis种子大小的变化。此外，我们探索了种子大小变化如何在有利的降水条件下（祖先地区）和不利的降水条件（在非本地地区）的条件下，影响多穗梭菌的幼苗存活。为此，我们按照原始，扩展和非本地范围内C. solstitialis的传播途径进行了种子收集。在本地，集合遵循海拔梯度。此外，我们还使用了C. solstitialis进行了温室实验种子大小和加水量不同的种群模拟了安纳托利亚和阿根廷的降水模式。低海拔祖先种群的种子比其他研究种群的种子小。同样，在非自然种群主要来源的高程种群中，种子种群的大小与所有种群相似，但其中一个非原生种群的种子进一步增加。种子大小的增加因此可追踪至多孢梭菌的范围扩展。在所有三个范围内，种子大小均随海拔升高而增加，表明对该梯度的收敛响应。仅在阿根廷条件下，较大种子的幼苗比较小种子的幼苗具有更大的存活率。因此，拥有大量种子的种群可能有助于在该非本地区域定居。我们的发现表明，大种子种群的古老和近来的传播有助于解释所报道的全球种子尺寸散布模式和全球梭子蟹的分布。