Protists are important microbial consumers and phototrophs in terrestrial ecosystems and play pivotal roles in nutrient cycling and plant performance. The predation pressure of protists significantly impacts the composition and function of microorganisms, and in turn bacteria and fungi, as the key food sources of protists, may shape the distribution of protists. However, how trophic interactions (i.e. biotic factors), together with environmental factors, regulate the community structure and functional traits of protists in natural soil ecosystems – with no or limited anthropogenic impacts - remains largely unknown. Here, we assessed the influences of biotic (vegetation types, bacteria, fungi and invertebrates) and abiotic factors (climate and soil attributes) on the core protist community using metabarcoding sequencing of 258 soil samples at a large scale. Core protists, representing abundant and ubiquitous phylotypes, were comprised of two major functional groups including consumers and phototrophs and were taxonomically dominated by supergroups Alveolata, Rhizaria and Archaeplastida. Soil invertebrate and bacterial communities were identified as the top predictors for the biogeographic pattern of core consumers, while the diversity and composition of core phototrophs were best predicted by mean annual temperature. Our study provides novel insights into the importance of biotic (trophic regulations) and abiotic factors in structuring core soil protist communities, and advances our understanding of the community assembly of consumer and phototrophic protists in the terrestrial ecosystems.

原生生物是陆地生态系统中重要的微生物消费者和光养生物，在养分循环和植物性能中起着关键作用。原生生物的捕食压力显着影响微生物的组成和功能，而细菌和真菌作为原生生物的主要食物来源，可能会影响原生生物的分布。然而，营养相互作用（即生物因素）与环境因素如何在自然土壤生态系统中调节原生生物的群落结构和功能特征——没有人为影响或人为影响有限——仍然很大程度上未知。在这里，我们评估了生物（植被类型、细菌、真菌和无脊椎动物）和非生物因素（气候和土壤属性）的核心原生生物群落使用元条形码测序在大规模 258 土壤样本。代表丰富和普遍存在的系统发育型的核心原生生物由两个主要功能群组成，包括消费者和光养生物，并且在分类学上以超群 Alveolata、Rhizaria 和 Archaeplastida 为主。土壤无脊椎动物和细菌群落被确定为核心消费者生物地理格局的主要预测因子，而核心光养生物的多样性和组成最好通过年平均温度进行预测。我们的研究为生物（营养调节）和非生物因素在构建核心土壤原生生物群落中的重要性提供了新的见解，