Neacă Ana-Maria, Meis Julia, Knight Tiffany, Rakosy Demetra
Faculty of Biology and Geology, Babeș-Bolyai University, Cluj-Napoca, Romania.
Institute of Biology, Martin Luther University Halle-Wittenberg, Halle, Germany.
PeerJ. 2024 Feb 29;12:e16900. doi: 10.7717/peerj.16900. eCollection 2024.
Land management change towards intensive grazing has been shown to alter plant and pollinator communities and the structure of plant-pollinator interactions in different ways across the world. Land-use intensification in Eastern Europe is shifting highly diverse, traditionally managed hay meadows towards intensive pastures, but few studies have examined how this influences plant-pollinator networks. We hypothesized that the effects of intensive grazing on networks will depend on how plant communities and their floral traits change.
We investigated plant and pollinator diversity and composition and the structure of plant-pollinator interactions near Sibiu, Romania at sites that were traditionally managed as hay meadows or intensive pastures. We quantified the identity and abundance of flowering plants, and used transect walks to observe pollinator genera interacting with flowering plant species. We evaluated the effects of management on diversity, composition and several indices of network structure.
Pollinator but not plant diversity declined in pastures and both plant and pollinator taxonomic composition shifted. Functional diversity and composition remained unchanged, with rather specialized flowers having been found to dominate in both hay meadows and pastures. was found to be the most abundant pollinator. Its foraging preferences played a crucial role in shaping plant-pollinator network structure. thus preferred the highly abundant in hay meadows, leading to hay meadows networks with lower Shannon diversity and interaction evenness. In pastures, however, it preferred less abundant and more generalized flower resources. With pollinators being overall less abundant and more generalized in pastures, we found that niche overlap between plants was higher.
With both hay meadows and pastures being dominated by plant species with similar floral traits, shifts in pollinator preferences seem to have driven the observed changes in plant-pollinator interaction networks. We thus conclude that the effects of grazing on pollinators and their interactions are likely to depend on the traits of plant species present in different management types as well as on the effects of grazing on plant community composition. We thereby highlight the need for better understanding how floral abundance shapes pollinator visitation rates and how floral traits may influence this relationship.
在全球范围内，土地管理方式向集约放牧转变已被证明会以不同方式改变植物和传粉者群落以及植物 - 传粉者相互作用的结构。东欧的土地利用集约化正在使高度多样化、传统管理的干草甸转变为集约牧场，但很少有研究考察这对植物 - 传粉者网络有何影响。我们假设集约放牧对网络的影响将取决于植物群落及其花部特征如何变化。
我们在罗马尼亚锡比乌附近，对传统管理为干草甸或集约牧场的地点，调查了植物和传粉者的多样性、组成以及植物 - 传粉者相互作用的结构。我们对开花植物的种类和丰度进行了量化，并通过样带行走观察与开花植物物种相互作用的传粉者属。我们评估了管理方式对多样性、组成以及网络结构的几个指标的影响。
牧场中传粉者多样性下降，但植物多样性未下降，植物和传粉者的分类组成均发生了变化。功能多样性和组成保持不变，在干草甸和牧场中均发现相当特化的花朵占主导地位。 被发现是最丰富的传粉者。其觅食偏好对塑造植物 - 传粉者网络结构起到了关键作用。 因此在干草甸中更喜欢高度丰富的 ，导致干草甸网络具有较低的香农多样性和相互作用均匀度。然而，在牧场中，它更喜欢不太丰富且更具普遍性的花资源。由于牧场中的传粉者总体上不太丰富且更具普遍性，我们发现植物之间的生态位重叠更高。
由于干草甸和牧场均由具有相似花部特征的植物物种主导，传粉者偏好的变化似乎推动了观察到的植物 - 传粉者相互作用网络的变化。因此，我们得出结论，放牧对传粉者及其相互作用的影响可能取决于不同管理类型中存在的植物物种的特征以及放牧对植物群落组成的影响。我们从而强调需要更好地理解花的丰度如何塑造传粉者访花率以及花部特征可能如何影响这种关系。
