Abstract:

The norway rat (Rattus norvegicus) and the Asian house rat (Rattus tanezumi) are closely related species inhabiting the tropical region of Hainan. Microhabitat segregation is considered an important mechanism for their coexistence. The gut microbiota plays a crucial role in regulating host physiological functions and in adaptation to environmental changes. Therefore, comparing the differences in gut microbial composition and functions between the two closely related species in the same habitat is conducive to elucidating their coexistence mechanisms from a physiological perspective. To accurately identify species, this study combined morphological indicators and the COI gene DNA barcoding to distinguish two rodent species. The gut microbial community structure and its functional characteristics were analyzed using high‑throughput sequencing of 16S rDNA was used to analyze the gut microbial community structure and functional characteristics of the two rat species. The results showed that among 34 rats identified by COI gene sequencing, 27 were R. norvegicus and 7 R. tanezumi. Significant differences were observed in alpha diversity (Shannon index) and beta diversity of gut microbiota between the two species, while no significant differences were found between individuals of different sexes within the same species. Differences in the composition of gut microbiota at the phylum, family, and genus levels, as well as functional predictions, revealed unique ecological adaptations of each species. Specifically, R. norvegicus exhibited higher abundances of Pseudomonadota, Lactobacillaceae, and Lactobacillus, reflecting an omnivorous tendency. In contrast, the ratio of Bacillota to Bacteroidota in the R. tanezumi was higher, and the abundance of fiber‑degrading bacteria, such as Muribaculaceae and Lachnospiraceae, also increased. Additionally, the carbon metabolism and biosynthesis of amino acids pathways were enriched in R. tanezumi, indicating a stronger herbivorous tendency. This study demonstrates that there is a significant difference in the structure and function of gut microbiota between R. norvegicus and R. tanezumi, suggesting divergences in their dietary preferences and ecological adaptation strategies. This study proposes that differences in intestinal microbiota, together with the synergistic effects of microhabitat segregation, reduce interspecific competition and promote sympatric coexistence, thereby providing a new perspective for understanding the coexistence mechanisms of closely related rodent species in tropical regions.

Key words: Commensal rats, DNA barcoding, Congeneric species, Gut microbiota, Species coexistence, Ecological adaptation

摘要：

褐家鼠（Rattus norvegicus）和黄胸鼠（Rattus tanezumi）是海南热带地区近缘种，微环境分离被认为是共存的重要机制。肠道微生物在调节宿主生理功能和适应环境变化上发挥重要作用，因此，比较两鼠种同一生境下肠道微生物组成及功能差异，有助于从生理功能角度探讨其共存机制。为精准鉴定物种，本研究参考形态学指标，并结合COI基因DNA条形码技术区分捕获的鼠类物种。通过16S rDNA高通量测序分析，测定褐家鼠和黄胸鼠肠道微生物群落和功能特征。结果显示，经COI基因测序鉴定，确认34只家栖鼠中27只为褐家鼠、7只为黄胸鼠。黄胸鼠和褐家鼠肠道微生物的Alpha多样性（Shannon指数）和Beta多样性差异显著，而同种鼠不同性别的个体肠道微生物多样性无显著差异；两鼠种在门、科、属水平的差异及菌群功能预测显示不同鼠种独特的生态适应性，具体表现为褐家鼠肠道中假单胞菌门（Pseudomonadota）、乳杆菌科（Lactobacillaceae）、乳杆菌属（Lactobacillus）等丰度高，具有杂食倾向；而黄胸鼠肠道中芽孢杆菌门（Bacillota）/拟杆菌门（Bacteroidota）比值较高，鼠杆菌科（Muribaculaceae）和毛螺菌科（Lachnospiraceae）等纤维分解菌丰度高，碳代谢和氨基酸生物合成通路活跃，具有植食性倾向。本研究发现，褐家鼠和黄胸鼠肠道微生物结构和功能存在显著差异，说明两者在食性偏好与生态适应策略上存在分异。本研究提出，肠道微生物差异与微环境分离协同作用可能有利于减少种间竞争，促进同域共存，为热带地区近缘鼠类物种共存机制研究提供了新的视角。

关键词: 家栖鼠, DNA条形码, 近缘种, 肠道微生物, 物种共存, 生态适应