Thomassen Emil Ellegaard, Sigsgaard Eva Egelyng, Jensen Mads Reinholdt, Olsen Kent, Hansen Morten D D, Svenning Jens-Christian, Thomsen Philip Francis
Department of Biology, Aarhus University, Aarhus C, Denmark.
Department of Research and Collections, Natural History Museum Aarhus, Aarhus C, Denmark.
Mol Ecol. 2023 Apr;32(8):2071-2091. doi: 10.1111/mec.16847. Epub 2023 Feb 6.
Trophic rewilding is increasingly applied in restoration efforts, with the aim of reintroducing the ecological functions provided by large-bodied mammals and thereby promote self-regulating, biodiverse ecosystems. However, empirical evidence for the effects of megafauna introductions on the abundance and richness of other organisms such as plants and invertebrates, and the mechanisms involved still need strengthening. In this study, we use environmental DNA (eDNA) metabarcoding of dung from co-existing feral cattle and horses to assess the seasonal variation in plant diet and dung-associated arthropods and nematodes. We found consistently high diet richness of horses, with low seasonal variability, while the generally lower dietary diversity of cattle increased substantially during summer. Intriguingly, season-specific diets differed, with a greater proportion of trees in the horses' diet during winter, where cattle relied more on shrubs. Graminoids were predominantly found in the diet of horses, but were generally underrepresented compared to previous studies, possibly due to the high prevalence of forbs in the study area. Dung-associated arthropod richness was higher for cattle, largely due to a high richness of flies during summer. Several species of dung-associated arthropods were found primarily in dung from one of the two herbivores, and our data confirmed known patterns of seasonal activity. Nematode richness was constantly higher for horses, and nematode communities were markedly different between the two species. Our results demonstrate complementary effects of cattle and horses through diet differences and dung-associated invertebrate communities, enhancing our understanding of large herbivore effects on vegetation and associated biodiversity. These results are directly applicable for decision-making in rewilding projects, suggesting biodiversity-benefits by inclusion of functionally different herbivores.
营养物野化越来越多地应用于恢复工作中，目的是重新引入大型哺乳动物所提供的生态功能，从而促进自我调节、生物多样的生态系统。然而，关于大型动物引入对植物和无脊椎动物等其他生物的丰度和丰富度的影响以及相关机制的实证证据仍需加强。在本研究中，我们对共存的野牛和野马粪便进行环境DNA（eDNA）代谢条形码分析，以评估植物饮食以及与粪便相关的节肢动物和线虫的季节变化。我们发现马的饮食丰富度一直很高，季节变化较小，而牛的饮食多样性通常较低，但在夏季大幅增加。有趣的是，特定季节的饮食有所不同，冬季马的饮食中树木的比例更大，而牛则更多地依赖灌木。禾本科植物在马的饮食中占主导地位，但与之前的研究相比普遍占比不足，这可能是由于研究区域中杂草的高发生率。与牛粪相关的节肢动物丰富度更高，这主要是因为夏季苍蝇的丰富度很高。几种与粪便相关的节肢动物主要在两种食草动物之一的粪便中被发现，我们的数据证实了已知的季节性活动模式。马的线虫丰富度一直更高，并且两个物种之间的线虫群落明显不同。我们的结果表明，牛和马通过饮食差异以及与粪便相关的无脊椎动物群落产生互补效应，增进了我们对大型食草动物对植被和相关生物多样性影响的理解。这些结果可直接应用于野化项目的决策，表明纳入功能不同的食草动物对生物多样性有益。
