Research Institute of Wildlife Ecology, University of Veterinary Medicine, Vienna, Austria.
Konrad-Lorenz Institute of Ethology, University of Veterinary Medicine, Vienna, Austria.
PLoS One. 2021 Mar 29;16(3):e0248294. doi: 10.1371/journal.pone.0248294. eCollection 2021.
With increasing livestock numbers, competition and avoidance are increasingly shaping resource availability for wild ungulates. Shifts in the dietary niche of wild ungulates are likely and can be expected to negatively affect their fitness. The Mongolian Gobi constitutes the largest remaining refuge for several threatened ungulates, but unprecedentedly high livestock numbers are sparking growing concerns over rangeland health and impacts on threatened ungulates like the Asiatic wild ass (khulan). Previous stable isotope analysis of khulan tail hair from the Dzungarian Gobi suggested that they graze in summer but switch to a poorer mixed C3 grass / C4 shrub diet in winter, most likely in reaction to local herders and their livestock. Here we attempt to validate these findings with a different methodology, DNA metabarcoding. Further, we extend the scope of the original study to the South Gobi Region, where we expect higher proportions of low-quality browse in the khulan winter diet due to a higher human and livestock presence. Barcoding confirmed the assumptions behind the seasonal diet change observed in the Dzungarian Gobi isotope data, and new isotope analysis revealed a strong seasonal pattern and higher C4 plant intake in the South Gobi Region, in line with our expectations. However, DNA barcoding revealed C4 domination of winter diet was due to C4 grasses (rather than shrubs) for the South Gobi Region. Slight climatic differences result in regional shifts in the occurrence of C3 and C4 grasses and shrubs, which do not allow for an isotopic separation along the grazer-browser continuum over the entire Gobi. Our findings do not allow us to confirm human impacts upon dietary preferences in khulan as we lack seasonal samples from the South Gobi Region. However, these data provide novel insight into khulan diet, raise new questions about plant availability versus preference, and provide a cautionary tale about indirect analysis methods if used in isolation or extrapolated to the landscape level. Good concordance between relative read abundance of C4 genera from barcoding and proportion of C4 plants from isotope analysis adds to a growing body of evidence that barcoding is a promising quantitative tool to understand resource partitioning in ungulates.
随着牲畜数量的增加，竞争和回避越来越影响野生有蹄类动物的资源可用性。野生有蹄类动物的饮食生态位可能会发生变化，这可能会对它们的适应性产生负面影响。蒙古戈壁是几个濒危有蹄类动物的最大剩余避难所，但前所未有的高牲畜数量引发了人们对牧场健康和对亚洲野驴（蒙古野驴）等濒危有蹄类动物的影响的日益关注。以前对来自准噶尔戈壁的蒙古野驴尾巴毛发的稳定同位素分析表明，它们在夏季以草为食，但在冬季会转向较差的混合 C3 草/C4 灌木饮食，这很可能是对当地牧民及其牲畜的反应。在这里，我们试图用不同的方法，即 DNA metabarcoding，来验证这些发现。此外，我们将原始研究的范围扩展到南戈壁地区，由于人类和牲畜的存在，我们预计那里蒙古野驴冬季饮食中低质量的 browse 比例会更高。条形码证实了在准噶尔戈壁同位素数据中观察到的季节性饮食变化背后的假设，新的同位素分析显示，南戈壁地区冬季饮食中有很强的季节性模式和更高的 C4 植物摄入量，这与我们的预期一致。然而，DNA 条形码揭示了冬季饮食中 C4 的主导地位是由于南戈壁地区 C4 草（而不是灌木）。轻微的气候差异导致 C3 和 C4 草和灌木的区域性变化，这使得在整个戈壁地区无法沿着食草动物-食者连续体进行同位素分离。由于我们缺乏来自南戈壁地区的季节性样本，因此我们无法确认人类对蒙古野驴饮食偏好的影响。然而，这些数据为蒙古野驴的饮食提供了新的见解，提出了关于植物可利用性与偏好的新问题，并对间接分析方法提供了一个警示，如果单独使用或推断到景观水平。条形码中 C4 属的相对读丰度与同位素分析中 C4 植物的比例之间的良好一致性增加了越来越多的证据，证明条形码是一种很有前途的定量工具，可以用来了解有蹄类动物的资源分配。
