1. The role of biotic interactions in shaping species distributions is a cornerstone of biogeographic theory; yet, it remains elusive. Such interactions are more likely to have an influence on organisms with obligate associations, such as hosts and their parasites. Whereas abiotic conditions may affect the abundance and distribution of parasites in ways similar to free‐living species, attributes of the host could also play a part.
2. Here, we focus on parasitic water mites and their dragonfly and damselfly hosts, and use a hierarchical Bayesian model to examine the relative influence of the abiotic environment and biotic factors such as local host community structure and individual host characteristics on parasite intensity along a broad‐scale environmental gradient. Specifically, we assessed how climate, surrounding vegetation, water chemistry, host community structure as well as the relative abundance and body mass of host species affected the intensity of parasitism on individual hosts along a latitudinal gradient.
3. We found that water chemistry and body mass of the host were the best predictors of variation in parasite intensity among hosts. High parasite intensity was observed in hosts sampled from lakes with high pH, dissolved oxygen and conductivity. Additionally, we found that the intensity of parasitism was strongly influenced by host species identity. In particular, body mass, which shows strong phylogenetic signal, was negatively related to parasite intensity. It may be that larger species, or individuals within species, are more immune to high level of parasitism and/or body mass is correlated with other traits of the host which relate to immunity.
4. Considering both the abiotic environment and attributes of host species is necessary to understand why certain host individuals and locations exhibit more intense parasitism. Amid widespread decline of insect populations world‐wide, some of which are attributed to pathogens and parasites, models predicting rates of parasitism in space and time could become an essential tool for guiding management and conservation efforts.

中文翻译：

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系统发育上保守的宿主特征和局部非生物条件共同驱动了寄生虫强度的地理分布

1. 生物相互作用在塑造物种分布中的作用是生物地理学理论的基石。然而，它仍然难以捉摸。这种相互作用更可能对具有专性联系的生物（例如宿主及其寄生虫）产生影响。非生物条件可能以类似于自由生活物种的方式影响寄生虫的数量和分布，但寄主的属性也可能起作用。
2. 在这里，我们重点研究寄生螨，它们的蜻蜓和豆娘寄主，并使用分层贝叶斯模型研究非生物环境和生物因素（如当地寄主群落结构和个体寄主特征）对沿宽广的寄生虫强度的相对影响。规模环境梯度。具体来说，我们评估了气候，周围的植被，水化学，寄主群落结构以及寄主物种的相对丰度和体重如何沿纬度梯度影响单个寄主上的寄生虫强度。
3. 我们发现寄主的水化学和体重是寄主中寄生虫强度变化的最佳预测指标。从具有高pH，溶解氧和电导率的湖泊采样的宿主中观察到高寄生虫强度。此外，我们发现寄生虫的强度受到宿主物种同一性的强烈影响。特别是显示强烈的系统发生信号的体重与寄生虫强度呈负相关。可能是较大的物种或物种中的个体对高水平的寄生虫具有更高的免疫力，和/或体重与宿主的其他与免疫相关的特征相关。
4. 必须同时考虑非生物环境和寄主物种的属性，以了解为什么某些寄主个人和地点表现出更强烈的寄生性。在全世界昆虫种群普遍减少的情况下，其中一些归因于病原体和寄生虫，预测空间和时间寄生率的模型可能成为指导管理和保护工作的重要工具。