Data from: Migratory behavior predicts greater parasite diversity in ungulates

Long-distance animal movements can increase exposure to diverse parasites, but can also reduce infection risk through escape from contaminated habitats or culling of infected individuals. These mechanisms have been demonstrated within and between populations in single-host/single-parasite interactions, but how long-distance movement behaviors shape parasite diversity and prevalence across host taxa is largely unknown. Using a comparative approach, we analyze the parasite communities of 93 migratory, nomadic, and resident ungulate species. We find that migrants have higher parasite species richness than residents or nomads, even after considering other factors known to influence parasite diversity, such as body size and host geographic range area. Further analyses support a novel “environmental tracking” hypothesis, whereby migration allows parasites to experience environments favorable to transmission year-round. In addition, the social aggregation and large group sizes that facilitate migration might increase infection risk for migrants. In contrast, we find little support for previously-proposed hypotheses, including migratory escape and culling, in explaining the relationship between host movement and parasitism in mammals at this cross-species scale. Our findings, which support mechanistic links between long-distance movement and increased parasite richness at the species level, could help predict the effects of future environmental change on parasitism in migratory animals.动物长距离移动既可提升其接触多种寄生虫的概率，也可通过逃离污染栖息地或淘汰感染个体来降低感染风险。上述机制已在单宿主-单寄生虫互作的种群内部及种群间得到验证，但长距离移动行为如何塑造不同宿主类群的寄生虫多样性与感染率，目前仍不明晰。本研究采用比较研究法(comparative approach)，分析了93种迁徙、游牧与居留型有蹄类动物(ungulate)的寄生虫群落。研究发现，即便在控制了已知会影响寄生虫多样性的其他因素（如宿主体型与地理分布范围）后，迁徙型物种的寄生虫物种丰富度(parasite species richness)仍高于居留型或游牧型物种。进一步分析验证了一项全新的“环境追踪”假说，即迁徙行为可使寄生虫全年处于利于其传播的环境中。此外，助力迁徙的社会聚集行为与大种群规模，可能会提升迁徙个体的感染风险。与之相反，在本次跨物种尺度的哺乳动物宿主移动与寄生关系分析中，此前提出的迁徙逃逸(migratory escape)、个体淘汰(culling)等假说均未得到足够证据支持。本研究结果证实了物种层面长距离移动与寄生虫丰富度升高之间的机制性关联，或可用于预测未来环境变化对迁徙动物寄生状况的影响。