In agricultural landscapes, differences in floral resources provided by crops compared with adjacent habitats promote the spillover of pollinators seeking to fulfil their feeding needs. These foraging patterns play an important role in both crop production and wild plant fitness. However, in classical observational studies, pollinator spillover patterns may be confounded by differences in pollinator phenologies and population sizes. To avoid these confounding effects, we quantified the combined effect of relative floral availability and season on pollinator spillover between strawberry crops and adjacent pinewoods by using commercial bumblebee colonies. We used 60 colonies that were placed in 6 open polytunnel strawberry crops and in 8 pinewoods adjacent to crops in landscapes with either low or high berry (mostly strawberry) crop cover. We repeated the experiment in winter and in spring to account for differences in flower resource availability. While strawberries were in bloom during the entire study period, wild flowering plants were scarce and abundant in winter and in spring, respectively. Spillover in crops was quantified as the percentage of bumblebee individuals that carried pollen from non-berry flowers, while spillover in pinewoods was quantified as the percentage of individuals that carried pollen from berry flowers. Overall, 526 bumblebees were collected. We found them carrying the pollen of 15 plant taxa in winter and 39 in spring, in accordance with seasonal floral availability. In crop colonies, around 30% of bumblebees spilled over into non-berry habitats in winter and 78% in spring, regardless of crop cover in the surrounding landscape. However, in pinewood colonies, we found an interaction effect between season and crop cover: even though on average 34% of bumblebees spilled over into berry crops, in winter it was almost twice in landscapes with high crop cover. Spillover patterns mainly mirrored seasonal changes in floral availability between habitats.

中文翻译：

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草莓作物与邻近松林之间大黄蜂溢出的季节性

在农业景观中，与邻近栖息地相比，作物提供的花卉资源的差异促进了传粉媒介寻求满足其觅食需求的外溢。这些觅食模式在作物生产和野生植物健康方面都发挥着重要作用。然而，在经典的观察性研究中，传粉媒介的外溢模式可能会因传粉媒介物候和种群规模的差异而混淆。为了避免这些混杂影响，我们通过使用商业大黄蜂群，量化了相对花卉可用性和季节对草莓作物和相邻松林之间传粉媒介溢出的综合影响。我们使用了 60 个菌落，这些菌落被放置在 6 个开放的多隧道草莓作物和 8 个与作物相邻的松林中，这些松林与低或高浆果（主要是草莓）作物覆盖的景观中的作物相邻。我们在冬季和春季重复了实验，以解释花卉资源可用性的差异。虽然在整个研究期间草莓都在盛开，但冬季和春季的野生开花植物分别稀少和丰富。作物中的溢出被量化为携带来自非浆果花的花粉的大黄蜂个体的百分比，而在松林中的溢出被量化为携带来自浆果花的花粉的个体的百分比。总共收集了 526 只大黄蜂。根据季节性花卉供应情况，我们发现它们在冬季携带 15 种植物分类群的花粉，在春季携带 39 种植物分类群的花粉。在作物群落中，无论周围景观中的作物覆盖情况如何，大约 30% 的大黄蜂在冬季溢出到非浆果栖息地，而在春季则为 78%。然而，在松林群落中，我们发现了季节和作物覆盖率之间的交互作用：尽管平均 34% 的大黄蜂溢出到浆果作物中，但在作物覆盖率高的景观中，冬季这一比例几乎是两倍。溢出模式主要反映了栖息地之间花卉可用性的季节性变化。