Abstract: Climate and diet are important factors driving seasonal changes in gut microbiota of small herbivorous mammals. However, most previous studies rarely addressed abundant and rare taxa in gut microbiota. Here, we used plateau pika (Ochotona curzoniae) as a model and conducted 16S rRNA gene-based large-scale structural profiling to explore the seasonal differences (spring, summer, autumn, and winter) in microbial composition, diversity, and function in abundant and rare taxa. The results showed that the Shannon index of abundant and rare taxa was significantly higher in winter than in other seasons. However, the ACE index of abundant taxa was significantly lower in autumn than in other seasons while that of rare taxa was significantly higher in winter than in spring and summer. For the abundant taxa, the relative abundance of Bacteroidetes in winter and autumn was significantly higher than that in spring and summer, while for the rare taxa, the relative abundance of Bacteroidetes in summer and autumn was significantly higher than that in winter and spring. The relative abundance of the amino acid metabolism pathway in abundant taxa was significantly higher in winter than that in spring and summer, while the relative abundance of this pathway in rare taxa was significantly higher in spring than that in summer and autumn. Air temperature, precipitation, and vegetative nutrition were significantly associated with variations in the microbial composition of both abundant and rare taxa. The total explanation proportions of environmental variables to the changes of abundant and rare taxa were 18% (air temperature:3%; precipitation:4%; vegetative nutrition:10%; combined:1%) and 9% (air temperature:1%; precipitation:2%; vegetative nutrition:5%; combined:1%), respectively. The results indicate that abundant and rare taxa of gut microorganisms have different distribution patterns, seasonal characteristics, and contributions to the entire microbial variation. The abundant taxa were more strongly influenced by environmental variables, reflecting the inconsistency in responses of different gut microbial taxa to seasonal changes. This study promotes our understanding of seasonal processes and environmental adaptability of animal's gut microbiota.

Key words: Gut microbiota, 16S rRNA gene, Abundant and rare taxa, Seasonality, Plateau pika (Ochotona curzoniae)

摘要： 气候及食物是驱动植食性小哺乳动物肠道菌群产生季节性变化的重要因素。然而，此类研究很少涉及肠道丰富及稀有微生物类群。本文以高原鼠兔（Ochotona curzoniae）为对象，通过16S rRNA基因测序和分析，探讨丰富及稀有肠道微生物类群的结构组成、多样性指数及功能在春、夏、秋、冬四季的变化特征。结果显示，丰富类群对菌群主要门和功能的季节性变异贡献大于稀有类群，稀有类群对菌群OTU和alpha多样性的变异贡献大于丰富类群。丰富类群和稀有类群的香农指数均在冬季显著高于其他季节；丰富类群的ACE指数在秋季显著低于其他季节，而稀有类群的ACE指数则在冬季显著高于春季和夏季。丰富类群中拟杆菌门（Bacteroidetes）的相对丰度在冬季和秋季显著高于春季和夏季，但在稀有类群中，夏季和秋季的相对丰度显著高于冬季和春季。丰富类群中氨基酸代谢通路的相对丰度在冬季显著高于春季和夏季，而在稀有类群中，其相对丰度在春季显著高于夏季和秋季。气温、降水量和植被中的营养物质与肠道菌群中丰富类群和稀有类群的变化均显著相关，环境变量对丰富类群和稀有类群变化的总解释率分别为18%（气温：3%；降水：4%；植被营养成分：10%；联合：1%）和9%（气温：1%；降水：2%；植被营养成分：5%；联合：1%）。以上结果表明肠道微生物中的丰富和稀有类群具有不同的分布模式和季节性特征，二者对整体菌群变异的贡献存在差异，环境因素更多地影响丰富类群，反映了肠道微生物不同类群对季节变化响应的非一致性。本研究增进了我们对哺乳动物肠道菌群季节性变化过程及环境适应性的认识。

关键词: 肠道微生物, 16S rRNA基因, 丰富和稀有类群, 季节性特征, 高原鼠兔