open access

https://doi.org/10.14943/doctoral.k14336

https://hdl.handle.net/2115/88951

都市化にともなう食性と寄生虫相の改変が同所的に生息する齧歯類の腸内細菌叢に及ぼす影響

英語

2021-03-25

Hokkaido University

169p.

Urban areas represent the most extreme form of anthropogenic ecosystem modification and have a profound effect on the wildlife that inhabit them. One area of recent but rapidly increasing interest is how urbanization affects the gut microbial communities of wild animals. The gut microbiota is pivotal for proper development, nutritional uptake, and immune system function and therefore essential to maintaining overall health. Plasticity in what constitutes a healthy gut microbial community may aid in the successful adaption to rapidly changing environments. Although studies have shown distinct changes in the gut microbiome of urban animals as compared to conspecifics in less disturbed habitats, few studies have investigated the underlying causes. Furthermore, differences in among species life histories such as dietary niche should impact how the gut microbiota is altered within urban environments due to host species-specific requirements in functionality, yet no study has investigatedchanges in multiple species experiencing the same degree of urbanization. The focus of this thesis is to understand how the gut microbiota of two sympatric species of rodents, the large Japanese field mouse (Apodemus speciosus) and the grey red-backed vole (Myodes rufocanus), is altered within urban ecosystems and what factors may be affecting those changes. In chapter 2, I characterize differences in the gut microbial community along the gastrointestinal tract (i.e. small intestine, cecum, colon, and rectum) of each species as well as between species differences in individuals from a natural environment (i.e. national forest). I found distinct differences between the small intestine and the cecum, colon, and rectum in both species as well as host species specific gut microbial communities in all gut regions. In chapter 3, I examined differences in dietary niche between urban and natural populations using stable isotope analysis and how it partially explains the altered gut microbiota of urban populations. Ifound that both rodent species experienced a dietary niche expansion, but that the expansion was much larger for the omnivorous A. speciosus. Furthermore, both species have undergone a shift towards consuming different dietary items in concordance with their life histories within the urban environment that may be related to novel anthropogenic food resources. These dietary changes were associated with specific changes in the gut microbial community structure; however, the relationship was not always clear. In chapter 4, I analyzed differences in the intestinal helminth communities between ecosystems and if their interactions with the gut microbial community is altered by urbanization, thereby affecting the gut microbiota. I found that urbanization had a negative impact on several species of helminths in both rodent species. Furthermore, I found that helminth prevalence and abundances were associated with changes in alpha diversity and community structure of the gut microbiota, but there was little consistency among gut region or ecosystem type suggesting a complex host-microbe-helminth-environmental interaction. Together, these results suggest that alteration of the gut microbiome in urban areas is species specific but determining the source of alteration is complex. By investigating multiple factors that may underlie these changes, it is possible to identify potential causes of dysbiosis as well as tools that could be used in management protocols to help urban wildlife maintain a proper gut microbiota, thereby improving the health of animals.

2021-03-25

甲第14336号

博士(環境科学)

(主査) 准教授 小泉 逸郎, 教授 野田 隆史, 教授 鈴木 仁, 准教授 中尾 亮（大学院獣医学研究院）

環境科学院（生物圏科学専攻）

博士論文

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