State Key Laboratory of Integrated Pest Management, Institute of Zoology, Chinese Academy of Sciences, Beijing, China.
Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
J Anim Ecol. 2019 Feb;88(2):302-314. doi: 10.1111/1365-2656.12920. Epub 2018 Nov 30.
The collapse of large wild herbivores with replacement of livestock is causing global plant community and diversity shifts, resulting in altered food availability and diet composition of other sympatric small herbivores in grasslands. How diet shifts affect the gut microbiota of small mammals and whether these changes may translate into complex interactions among coexisting herbivores remain largely unknown. We conducted both a field experiment and a laboratory diet manipulation experiment to test whether sheep grazing induces a diet shift and thus alters the gut microbiota of a small rodent species living in grassland. We found that enclosures subjected to grazing were mostly dominated by Stipa krylovii (accounting for 53.6% of the total biomass) and that voles consumed significantly more S. krylovii and less Cleistogenes squarrosa in grazed enclosures. Voles in grazing enclosures exhibited significantly lower abundances of Firmicutes, higher abundances of Bacteroidetes and significantly lower measurements of alpha diversity. The microbiota from voles in the grazed enclosures had a smaller and more simplified co-occurrence network with relatively higher percentage of positive interactions. Analysis based on dietary clusters indicated that grazing-induced changes in diet composition contributed to the distinct gut microbial community of voles in enclosures. We verified our findings using laboratory experiments, in which voles were exclusively fed C. squarrosa (high carbohydrate, high fibre and high in secondary compounds), S. krylovii (low carbohydrate, low fibre and low in secondary compounds) or Leymus chinensis (nutritionally intermediate). We observed that the gut microbiota of voles changed with the three different diets, supporting the idea that the effects of sheep grazing on the gut microbiota of Brandt's voles may be related to grazing-induced diet shifts. Our results highlighted the negative effects of livestock grazing on small mammals in grassland via changes in plant community and gut microbiota of small mammals and help to better understand the cascading consequences of realistic scenarios of world-wide decline in large wild herbivores.
大型野生草食动物的减少和牲畜的替代正在导致全球植物群落和多样性的转变，从而改变了草原中小草食动物的食物可利用性和饮食组成。饮食变化如何影响小型哺乳动物的肠道微生物群，以及这些变化是否可能转化为共存草食动物之间的复杂相互作用，在很大程度上仍然未知。我们进行了现场实验和实验室饮食处理实验，以测试绵羊放牧是否会引起饮食变化，从而改变生活在草原中的小型啮齿动物物种的肠道微生物群。我们发现，放牧围栏主要以芨芨草（占总生物量的 53.6%）为主，而在放牧围栏中，田鼠消耗的芨芨草明显更多，而少花棘豆则更少。在放牧围栏中的田鼠表现出较低的厚壁菌门丰度，较高的拟杆菌门丰度和较低的 alpha 多样性测量值。来自放牧围栏中的田鼠的微生物群具有更小且更简化的共生网络，相对较高的正相互作用百分比。基于饮食聚类的分析表明，放牧引起的饮食组成变化导致了围栏中田鼠肠道微生物群落的明显差异。我们使用实验室实验验证了我们的发现，在实验室实验中，田鼠仅喂食少花棘豆（高碳水化合物、高纤维和高次生化合物）、芨芨草（低碳水化合物、低纤维和低次生化合物）或羊草（营养中间）。我们观察到，田鼠的肠道微生物群随着三种不同的饮食而变化，这支持了绵羊放牧对布氏田鼠肠道微生物群的影响可能与放牧引起的饮食变化有关的观点。我们的结果强调了通过改变植物群落和小型哺乳动物的肠道微生物群，牲畜放牧对草原中小型哺乳动物的负面影响，并有助于更好地理解全球大型野生草食动物减少的现实情景下的级联后果。
