Flowering plants exhibit a wide variation in the resources they invest in dispersal structures (dispersal investment), but the environmental correlates still remain unclear in many cases. Canopy openness is predicted to be negatively correlated with dispersal investment, because selective pressures on increased dispersal investment, including host-specific natural enemies and the paucity and/or ephemerality of safe sites, will be more prevalent in shady sites. Here, we tested this prediction by firstly examining the correlation between dispersal investment and canopy openness as well as abundance of the representative natural enemy (rusts, Puccinia spp.) through seven populations of an ant-dispersed sedge, Carex lanceolata (Cyperaceae). Secondly we conducted a cafeteria experiment to verify the effect of intraspecific variation in dispersal investment on diaspore preferences of seed dispersing ants. Lastly, a seedling transplant experiment was performed to clarify whether seed dispersal distances by ants are sufficient to reduce infection by the rusts. We found a negative correlation between dispersal investment and canopy openness, thus supporting the prediction. Moreover, there were more signs of rust infection caused by Puccinia spp. on adult plant leaves in more shady sites. The cafeteria experiment showed that a large ant species (Formica japonica) with relatively long seed dispersal distances tended to prefer diaspores with greater dispersal investments, while smaller ant species with shorter dispersal distances preferred diaspores with lower dispersal investments. The seedling transplant experiment revealed that rust severity in sedge offspring was considerably reduced by the typical seed dispersal distance (ca. 4 m) afforded by the large ant species, F. japonica. The increased rust severity at shady sites, combined with the narrow dispersal ranges of rusts, can partially explain the negative correlation of dispersal investment with canopy openness. These results support the importance of canopy openness as a factor underlying the variations in dispersal investment seen among flowering plants.

开花植物在分散结构上投资的资源（分散投资）表现出很大的差异，但是在许多情况下，与环境的相关性仍然不清楚。冠层开放度预计将与分散投资负相关，因为对增加的分散投资的选择性压力（包括宿主特定的天敌以及安全场所的稀缺性和/或短暂性）将在阴暗场所更为普遍。在这里，我们通过首先检查分散分布投资与树冠开放度之间的相关性以及通过七个蚂蚁分散的莎草（Carex lanceolata）种群的代表性天敌（锈菌，锈菌属）的相关性，对这一预测进行了检验。（莎草科）。其次，我们进行了自助餐厅实验，以验证种子投资中种内变异对种子分散剂的水硬性偏好的影响。最后，进行了幼苗移植实验，以阐明蚂蚁传播种子的距离是否足以减少锈病的感染。我们发现分散投资与冠层开放度之间存在负相关关系，从而支持了这一预测。此外，还有更多由锈菌引起的锈病感染迹象。在成年植物叶片上的阴影较多。自助餐厅的实验表明，一种大型的蚂蚁物种（胶木种子散布距离相对较长的）倾向于选择散布投资较大的硬孢子，而散布距离较短的较小的蚂蚁物种则散布投资较低的假孢子。幼苗移植实验表明，大蚂蚁种类F提供的典型种子传播距离（约4 m）大大降低了莎草后代的锈病严重程度。粳稻。遮荫处锈病严重程度的提高，加上锈蚀的扩散范围狭窄，可以部分解释扩散投资与冠层开放度的负相关关系。这些结果支持冠层开放性的重要性，因为开放性是开花植物中分散投资变化的基础。