Competitive interactions between plants can affect patterns of allocation to reproductive structures through modulation of resource availability. As floral traits involved in plant attractiveness to pollinators can be sensitive to these resources, competition with any neighbouring species may influence the attractiveness of insect-pollinated plants. While pollination research has primarily focused on above-ground interactions, this study aims at investigating if the presence of a competitor plant can modulate neighbouring insect-pollinated plant attractiveness to pollinators and resulting fecundity, especially through below-ground competitive interactions for soil resources. We set up a plot experiment in which we grew an insect-pollinated plant, Sinapis alba (Brassicaceae), in a mixture dominated by a wind-pollinated plant, Holcus lanatus (Poaceae). Individuals of S. alba were either subjected to or isolated from (with buried tubes in the soil) below-ground competition. Across the flowering season, floral traits involved in attractiveness of S. alba and pollinator visitation were followed at the plot and plant level to investigate different scales of attractiveness. At the end of the experiment, seeds were harvested to assess plant fecundity. Competition had a significant negative effect on plot and plant floral display size as well as flower size while nectar traits were not affected. When plants of S. alba were in competition, the time to first visit was altered: the proportion of plots that received a visit was smaller for a given time; in other words, it took more time for a given proportion of plots to be visited and some plots were even never visited. Moreover, pollinators made fewer visits per plots. The proportion of viable seeds produced by S. alba in competition was lower and probably linked to the competition itself rather than changes in pollinator visitation. This study suggests that competitive interactions between plants can modulate pollination interactions even when competing plant species are not insect-pollinated.

中文翻译：

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地下竞争改变了昆虫授粉植物对传粉媒介的吸引力。

植物之间的竞争性相互作用可以通过调节资源可用性来影响分配给生殖结构的模式。由于涉及植物对传粉媒介的吸引力的花卉性状可能对这些资源敏感，因此与任何邻近物种的竞争都可能影响昆虫授粉植物的吸引力。虽然授粉研究主要集中于地上的相互作用，但本研究旨在调查竞争植物的存在是否可以调节邻近的昆虫授粉植物对授粉者的吸引力和繁殖力，尤其是通过地下对土壤资源的竞争性相互作用。我们建立了一个地块实验，在该实验中我们种了一种昆虫授粉的植物Sinapis alba（芸苔科），以风传粉植物Holcus lanatus（禾本科）为主导的混合物。白化链球菌个体经历了地下竞争或从地下竞争中分离（通过埋在土壤中的管子）。在整个开花季节，在地块和植物水平上都跟踪了与S. alba的吸引力和传粉媒介访花有关的花卉性状，以研究不同程度的吸引力。在实验结束时，收获种子以评估植物繁殖力。竞争对地块和植物的花样大小以及花大小有显着的负面影响，而花蜜性状不受影响。当S. alba的植物在比赛中，第一次访问的时间发生了变化：在特定时间内，访问一次的地块所占的比例较小；换句话说，要花更多的时间来访问给定比例的地块，甚至有些地块甚至从未被访问过。此外，授粉者每块地的造访次数较少。链球菌在竞争中产生的可行种子的比例较低，可能与竞争本身有关，而不是与传粉媒介访视的变化有关。这项研究表明，即使竞争植物没有经过昆虫授粉，植物之间的竞争相互作用也可以调节授粉相互作用。