Prior work has shown a positive scaling relationship between vertebrate body size, human height, and gut microbiome alpha diversity. This observation mirrors commonly observed species area relationships (SAR) in many other ecosystems. Here, we expand these observations to several large data sets, showing that this size-diversity scaling relationship is independent of relevant covariates, like diet, body mass index, age, sex, bowel movement frequency, antibiotic usage, and cardiometabolic health markers. Island biogeography theory (IBT), which predicts that larger islands tend to harbor greater species diversity through neutral demographic processes, provides a simple mechanism for positive SARs. Using gut-adapted IBT model, we demonstrated that increasing the length of a flow-through ecosystem led to increased species diversity, closely matching our empirical observations. We delve into the possible clinical implications of these SARs in the American Gut cohort. Consistent with prior observations that lower alpha diversity is a risk factor for Clostridioides difficile infection (CDI), we found that individuals who reported a history of CDI were shorter than those who did not and that this relationship was mediated by alpha diversity. We observed that vegetable consumption had a much stronger association with CDI history, which was also partially mediated by alpha diversity. In summary, we find that the positive scaling observed between body size and gut alpha diversity can be plausibly explained by a gut-adapted IBT model, may be related to CDI risk, and vegetable intake appears to independently mitigate this risk, although additional work is needed to validate the potential disease risk implications.

中文翻译：

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岛屿生物地理学理论为为什么较大的脊椎动物和较高的人类拥有更多样化的肠道微生物群提供了合理的解释


先前的研究表明，脊椎动物的体型、人类身高和肠道微生物组α多样性之间存在正相关关系。这一观察结果反映了许多其他生态系统中常见的物种面积关系（SAR）。在这里，我们将这些观察扩展到几个大数据集，表明这种体型-多样性尺度关系独立于相关协变量，如饮食、体重指数、年龄、性别、排便频率、抗生素使用和心脏代谢健康标志物。岛屿生物地理学理论 (IBT) 预测，较大的岛屿往往会通过中性的人口统计过程拥有更大的物种多样性，为积极的 SAR 提供了一种简单的机制。使用肠道适应 IBT 模型，我们证明增加流通生态系统的长度会导致物种多样性增加，这与我们的经验观察非常吻合。我们深入研究了这些 SAR 在美国肠道队列中可能的临床意义。与先前的观察结果一致，即较低的α多样性是艰难梭菌感染（CDI）的危险因素，我们发现报告有CDI病史的个体比没有患CDI病史的个体矮，并且这种关系是由α多样性介导的。我们观察到蔬菜消费与 CDI 历史有更强的关联，这也部分由 α 多样性介导。总之，我们发现，在体型和肠道 α 多样性之间观察到的正比例可以通过肠道适应的 IBT 模型合理地解释，可能与 CDI 风险有关，并且蔬菜摄入似乎可以独立地减轻这种风险，尽管需要进行额外的工作需要验证潜在的疾病风险影响。