Sympatric Yaks and Plateau Pikas Promote Microbial Diversity and Similarity by the Mutual Utilization of Gut Microbiota.

Haibo Fu,Chuanfa Liu,Yanming Zhang,Qi Cheng,Chao Fan,Liangzhi Zhang,He Zhang,Wenjing Li

doi:10.3390/microorganisms9091890

Abstract

Interactions between species provide the basis for understanding coexisting mechanisms. The plateau pika (Ochotona curzoniae) and the yak (Bos grunniens) are considered competitors because they have shared habitats and consumed similar food on the Qinghai–Tibetan Plateau for more than 1 million years. Interestingly, the population density of plateau pikas increases with yak population expansion and subsequent overgrazing. To reveal the underlying mechanism, we sequenced the fecal microbial 16S rDNA from both sympatric and allopatric pikas and yaks. Our results indicated that sympatry increased both gut microbial diversity and similarity between pikas and yaks. The abundance of Firmicutes, Proteobacteria, Cyanobacteria, and Tenericutes decreased, while that of Verrucomicrobia increased in sympatric pikas. As for sympatric yaks, Firmicutes, Bacteroidetes, and Spirochaetes significantly increased, while Cyanobacteria, Euryarchaeota, and Verrucomicrobia significantly decreased. In sympatry, plateau pikas acquired 2692 OTUs from yaks, and yaks obtained 453 OTUs from pikas. The predominant horizontally transmitted bacteria were Firmicutes, Bacteroidetes, Verrucomicrobia, and Proteobacteria. These bacteria enhanced the enrichment of pathways related to prebiotics and immunity for pikas, such as heparin sulfate, heparin, chitin disaccharide, chondroitin-sulfate-ABC, and chondroitin-AC degradation pathways. In yaks, the horizontally transmitted bacteria enhanced pathways related to hepatoprotection, xenobiotic biodegradation, and detoxification. Our results suggest that horizontal transmission is a process of selection, and pikas and yaks tend to develop reciprocity through the horizontal transmission of gut microbiota.

Highlights

In nature, organisms coexist through complex interspecific interactions, such as competition, predation, commensalism, and mutualism, which contribute to the biodiversity and stability of biocoenosis [1,2]
We have found that plateau pikas survive in winter by eating yak feces when food is short, and horizontal transmission of gut microbiota occurred during this process [24]; these scenes made us question if pikas eat yak feces in summer, or if horizontal transmission of gut microbiota occurred in summer
We identified horizontally transmitted operational taxonomic units (OTUs) by comparing the gut microbiota of yaks and plateau pikas following the methods described in a previous study [25]

Summary

Introduction

Organisms coexist through complex interspecific interactions, such as competition, predation, commensalism, and mutualism, which contribute to the biodiversity and stability of biocoenosis [1,2]. Traditional studies have generally assumed that sympatric herbivores are competitors because they consume similar plants and share habitats, leading to a high overlap of diet and space niche [1,3]. Livestock promotes outbreaks of sympatric locusts (Oedaleus asiaticus) under heavy grazing conditions [4]. Wild ungulates positively influence cattle by enhancing the dietary crude protein content during the wet season, while the opposite interaction occurs during the dry season [5]. These studies have indicated that environmental factors may modify interspecific interactions

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Discussion

Conclusion