Peters Birte, Leonhardt Sara Diana, Schloter Michael, Keller Alexander
Department for Animal Ecology and Tropical Biology, Biocenter, University of Würzburg, Würzburg, Germany.
Center for Computational and Theoretical Biology, University of Würzburg, Würzburg, Germany.
Front Microbiol. 2025 Jan 9;15:1513096. doi: 10.3389/fmicb.2024.1513096. eCollection 2024.
The global decline in biodiversity and insect populations highlights the urgent need to conserve ecosystem functions, such as plant pollination by solitary bees. Human activities, particularly agricultural intensification, pose significant threats to these essential services. Changes in land use alter resource and nest site availability, pesticide exposure and other factors impacting the richness, diversity, and health of solitary bee species. In this study, we investigated yet another facet currently less well investigated in such context: Microbial communities associated with wild bees play crucial roles in larval development, metabolism, immunity and overall bee health. However, the drivers and dynamics of healthy microbiome in solitary bees are still poorly understood, especially regarding the direct and indirect effects of land use on the diversity and composition of these microbial communities.
We examined bacterial communities in the offspring and nest materials of the Megachilid trap-nesting solitary bee, Osmia bicornis, along a gradient of land use intensification by 16S rRNA gene metabarcoding. Given that landscape composition, climatic conditions, and food resources are known to influence microbial compositions in solitary bee species, we hypothesized that land use changes would alter resources available for food and nest material collection and thereby affecting the microbiomes in offspring and their nest environments. We anticipated reduced microbial diversity and altered composition with increased land use intensification, which is known to decrease the number and diversity of resources, including the pool of floral and soil bacteria in the surrounding environment.
As expected, we observed significant shifts in the bacterial composition and diversity of bees and their nests across varying degrees of land use intensity, differing in management types and the availability of flowers. The Shannon diversity of bacteria in nest materials (larval pollen provision, soil nest enclosure) and larval guts decreased with increasing land use intensity. However, the pupae microbiome remained unaffected, indicating a reorganization of the microbiome during metamorphosis, which is not significantly influenced by land use and available resources.
Our findings provide new insights into the factors shaping environmental transmission and changes in solitary bee microbiomes. This understanding is crucial for comprehending the impacts of intensive land use on wild bee health and developing strategies to mitigate these effects.
全球生物多样性和昆虫数量的下降凸显了保护生态系统功能的迫切需求，比如独居蜂对植物的授粉作用。人类活动，尤其是农业集约化，对这些重要服务构成了重大威胁。土地利用的变化改变了资源和巢穴的可用性、农药暴露以及其他影响独居蜂物种丰富度、多样性和健康状况的因素。在本研究中，我们调查了在此背景下目前较少被深入研究的另一个方面：与野生蜜蜂相关的微生物群落对幼虫发育、新陈代谢、免疫和蜜蜂整体健康起着关键作用。然而，人们对独居蜂健康微生物群的驱动因素和动态变化仍知之甚少，特别是关于土地利用对这些微生物群落多样性和组成的直接和间接影响。
我们通过16S rRNA基因代谢条形码技术，沿着土地利用集约化梯度，研究了切叶蜂科筑巢独居蜂角额壁蜂后代及其巢穴材料中的细菌群落。鉴于已知景观组成、气候条件和食物资源会影响独居蜂物种的微生物组成，我们假设土地利用变化会改变用于采集食物和巢穴材料的可用资源，从而影响后代及其巢穴环境中的微生物群。我们预计随着土地利用集约化程度的增加，微生物多样性会降低，组成会发生改变，因为土地利用集约化已知会减少资源的数量和多样性，包括周围环境中的花卉和土壤细菌库。
正如预期的那样，我们观察到在不同程度的土地利用强度下，蜜蜂及其巢穴的细菌组成和多样性发生了显著变化，这些土地利用强度在管理类型和花卉可用性方面存在差异。巢穴材料（幼虫花粉供应、土壤巢穴外壳）和幼虫肠道中细菌的香农多样性随着土地利用强度的增加而降低。然而，蛹的微生物群未受影响，这表明在变态过程中微生物群发生了重组，且这种重组不受土地利用和可用资源的显著影响。
我们的研究结果为影响独居蜂微生物群环境传播和变化的因素提供了新的见解。这种理解对于理解集约土地利用对野生蜜蜂健康的影响以及制定减轻这些影响的策略至关重要。
