Mediterranean Institute for Advanced Studies (UIB-CSIC), Global Change Research Group, C/Miquel Marquès 21, 07190, Esporles, Balearic Islands, Spain.
Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, 1432, Ås, Norway.
Sci Rep. 2020 Jul 2;10(1):10872. doi: 10.1038/s41598-020-67447-y.
Understanding the effects of landscape fragmentation on global bumblebee declines requires going beyond estimates of abundance and richness and evaluating changes in community composition and trophic and competitive interactions. We studied the effects of forest fragmentation in a Scandinavian landscape that combines temperate forests and croplands. For that, we evaluated how forest fragmentation features (patch size, isolation and shape complexity, percentage of forest in the surroundings) as well as local flowering communities influenced bumblebee abundance, richness and community composition in 24 forest patches along a fragmentation gradient. In addition, we assessed the effect of fragmentation on bumblebee-plant network specialization (H'), and potential inter- and intraspecific competition via shared plants. Patch isolation was associated with lower bumblebee abundance, whereas flower density was positively related to both bumblebee abundance and richness. Overall, forest fragmentation reduced the abundance of forest-specialists while increasing the abundance of open-habitat species. Patches with complex shapes and few flowers showed more generalized bumblebee-plant networks (i.e., fewer specific interactions). Patch shape complexity and the percentage of forest also modified inter- and intraspecific competitive interactions, with habitat generalists outcompeting forest specialists in fragmented areas. Understanding these mechanisms is necessary to anticipate to the impact of forest fragmentation on bumblebee decline.
理解景观破碎化对全球熊蜂衰退的影响需要超越丰度和丰富度的估计，评估群落组成和营养及竞争相互作用的变化。我们研究了斯堪的纳维亚景观中森林破碎化的影响，该景观结合了温带森林和农田。为此，我们评估了森林破碎化特征（斑块大小、隔离度和形状复杂性、周围森林的比例）以及当地的开花群落如何影响 24 个森林斑块中沿破碎化梯度的熊蜂丰度、丰富度和群落组成。此外，我们评估了破碎化对熊蜂-植物网络专业化（H'）的影响，以及通过共享植物的种间和种内竞争的潜在影响。斑块隔离与熊蜂丰度降低有关，而花密度与熊蜂丰度和丰富度呈正相关。总体而言，森林破碎化减少了森林专化种的丰度，而增加了开阔生境物种的丰度。形状复杂且花少的斑块表现出更普遍的熊蜂-植物网络（即，较少的特定相互作用）。斑块形状复杂性和森林比例也改变了种间和种内竞争相互作用，在破碎化地区，栖息地广适种竞争胜过森林专化种。了解这些机制对于预测森林破碎化对熊蜂衰退的影响是必要的。
