Endotherms recently expanding to cold environments generally exhibit strong physiological acclimation to sustain high body temperature. During this process, gut microbes likely play a considerable role in host physiological functions, including digestion and thermogenesis. The Light-vented bulbul Pycnonotus sinensis represents one of such a species. It used to be restricted to the Oriental realm, but expanded its distribution range north to the Palearctic areas during the past few decades. Here, we explored the seasonal dynamics of the resting metabolic rate (RMR) and microbiota for local and newly colonized populations of the species. Our results showed that the mass-adjusted RMR and body mass were positively correlated with latitude variations in both seasons. Consistently, the gut microbiota showed corresponding variation to the northern cold environments. In the two northern populations, the alpha diversity decreased compared with those of two southern populations. Significant differences were detected in dominant phyla, such as Firmicutes, Bacteroidetes, Proteobacteria and Desulfobacterota in both seasons. The core microbiota showed geographic differences in the winter, including the elevated relative abundance of 5 species in northern populations. Finally, to explore the link between microbial communities and host metabolic thermogenesis, we conducted a correlation analysis between microbiota and mass-adjusted RMR. We found that more genera were significantly correlated with mass-adjusted RMR in the wintering season compared to the breeding season (71 versus 23). These results suggest that microbiota of the lighted-vented bulbul linked with thermogenesis in diversity and abundance under northward expansion.

中文翻译：

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近期向北范围扩张期间，光通气鹎的代谢和微生物变化

最近扩展到寒冷环境的吸热动物通常表现出强烈的生理适应性以维持高体温。在此过程中，肠道微生物可能在宿主生理功能（包括消化和产热）中发挥重要作用。光通气鹎 Pycnonotus sinensis 代表了这样一个物种。它过去只局限于东方领域，但在过去的几十年里，它的分布范围向北扩展到古北界地区。在这里，我们探索了该物种当地和新殖民种群的静息代谢率 (RMR) 和微生物群的季节性动态。我们的结果表明，质量调整后的 RMR 和体重在两个季节都与纬度变化呈正相关。始终如一，肠道微生物群显示出与北方寒冷环境相应的变化。在两个北方种群中，与两个南方种群相比，alpha 多样性有所降低。在两个季节中检测到优势门的显着差异，例如 Firmicutes、Bacteroidetes、Proteobacteria 和 Desulfobacterota。核心微生物群在冬季表现出地理差异，包括北部种群中 5 个物种的相对丰度增加。最后，为了探索微生物群落与宿主代谢产热之间的联系，我们进行了微生物群与质量调整 RMR 之间的相关性分析。我们发现与繁殖季节相比，越冬季节更多的属与质量调整后的 RMR 显着相关（71 对 23）。