BACKGROUND The wild radishes, Raphanus raphanistrum and R. pugioniformis (Brassicaceae) are native to the East Mediterranean region. However, whereas R. raphanistrum is widely distributed worldwide, the endemic R. pugioniformis is limited to specific habitats. In R. raphanistrum the diaspores of the indehiscent fruits comprise glabrous, light, single-seeded segments, whereas the intact fruits of R. pugioniformis are heavy and covered with spiny backward-pointing trichomes. We aimed to investigate whether the structure of the diaspores was directly associated with long- and short-range dispersal in R. raphanistrum and R. pugioniformis, respectively. We further surveyed within-population spatial distributions, to test the hypothesis that short- and long-range dispersal contribute to a patchy vs. uniform distribution patterns of R. pugioniformis and R. raphanistrum, respectively. RESULTS The results indicated that dispersal by wind and run-off water was substantially lower for diaspores of R. pugioniformis than for those of R. raphanistrum diaspores. Supporting the hypothesis that backward-pointing trichomes promote adherence to soil particles, the displacement on soil surface of R. pugioniformis fruits depended on their orientation relative to wind direction. Furthermore, trichome removal from fruits of R. pugioniformis significantly reduced wind velocity needed to remove fruits that were placed on soils typical of the species' natural habitats. The spatial-distribution survey results indicated a patchy distribution of R. pugioniformis populations as compared with the more uniform arrangement in the studied populations of R. raphanistrum; consistent with the unidirectional vs. homogeneous wind dispersal of the respective diaspores, with respect to wind direction. In addition, R. pugioniformis population sizes changed less between years than those of R. raphanistrum. CONCLUSIONS Overall, our results indicate that fruit structure is strongly linked to dispersal ability and spatial distribution of the two closely related wild radish species. Whereas R. raphanistrum inhabits homogenous sandy soil habitats, the distribution range of R. pugioniformis includes heterogeneous environments in which growth niches are scarcer. We suggest that the different modes of dispersal have evolved as adaptive traits appropriate to the species' specific habitats.

中文翻译：

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野生萝卜的种子传播及其与种群内部空间分布的关系。

背景技术野生萝卜，Raphanus raphanistrum和R. pugioniformis（十字花科）起源于东地中海地区。然而，尽管R. raphanistrum在世界范围内广泛分布，但地方性的R. pugioniformis仅局限于特定的栖息地。在R. raphanistrum中，不裂实的水果的孢子包括无毛的，轻的，单种子的节，而完整的R. pugioniformis的果实很重，并覆盖着多刺的向后毛状体。我们旨在研究在R. raphanistrum和R. pugioniformis中，diaspores的结构是否分别与长程和短程分散直接相关。我们进一步调查了人口内部空间分布，以检验以下假设：近距离和远距离分散会导致R的斑块分布与均匀分布模式。pugioniformis和R. raphanistrum。结果结果表明，风和径流水的扩散对R. pugioniformis diaspores来说要比R. raphanistrum diaspores更低。支持倒向毛状体促进对土壤颗粒的附着这一假说的支持，形果果实在土壤表面的位移取决于它们相对于风向的方向。此外，从三角叶罗汉果的果实中去除三角毛显着降低了去除放置在该物种自然栖息地典型土壤上的果实所需的风速。空间分布调查结果表明，与所研究的R. raphanistrum种群中更均匀的排列相比，R。pugioniformis种群的分布是零散的。相对于风向而言，与各个渗透孔的单向与均匀风散布相一致。此外，多年生的R. pugioniformis种群大小的变化小于R. raphanistrum。结论总体而言，我们的结果表明果实结构与两个紧密相关的野生萝卜物种的扩散能力和空间分布密切相关。R. raphanistrum居住在同质的沙质土壤生境中，而R. pugioniformis的分布范围包括生长环境较为稀缺的异质环境。我们认为，不同的传播方式已经发展成为适合该物种特定栖息地的适应性状。多年生肺小球虫种群的变化小于R. raphanistrum。结论总体而言，我们的结果表明果实结构与两个紧密相关的野生萝卜物种的扩散能力和空间分布密切相关。R. raphanistrum居住在同质的沙质土壤生境中，而R. pugioniformis的分布范围包括生长环境较为稀缺的异质环境。我们认为，不同的传播方式已经发展成为适合物种特定栖息地的适应性状。多年生肺小球虫种群的变化小于R. raphanistrum。结论总体而言，我们的结果表明果实结构与两个紧密相关的野生萝卜物种的扩散能力和空间分布密切相关。R. raphanistrum居住在同质的沙质土壤生境中，而R. pugioniformis的分布范围包括生境稀少的异质环境。我们认为，不同的传播方式已经发展成为适合物种特定栖息地的适应性状。萝卜生活在同质的沙土生境中，R。pugioniformis的分布范围包括异质环境，在这些环境中生境稀缺。我们认为，不同的传播方式已经发展成为适合物种特定栖息地的适应性状。萝卜生活在同质的沙土生境中，R。pugioniformis的分布范围包括生长环境较为稀缺的异质环境。我们认为，不同的传播方式已经发展成为适合物种特定栖息地的适应性状。