Data from: Evolutionary associations between host traits and parasite load: insights from Lake Tanganyika cichlids

Parasite diversity and abundance (parasite load) vary greatly among host species. However, the influence of host traits on variation in parasitism remains poorly understood. Comparative studies of parasite load have largely examined measures of parasite species richness and are predominantly based on records obtained from published data. Consequently, little is known about the relationships between host traits and other aspects of parasite load, such as parasite abundance, prevalence and aggregation. Meanwhile, understanding of parasite species richness may be clouded by limitations associated with data collation from multiple independent sources. We conducted a field study of Lake Tanganyika cichlid fishes and their helminth parasites. Using a Bayesian phylogenetic comparative framework, we tested evolutionary associations between five key host traits (body size, gut length, diet breadth, habitat complexity and number of sympatric hosts) predicted to influence parasitism, together with multiple measures of parasite load. We find that the number of host species that a particular host may encounter due to its habitat preferences emerges as a factor of general importance for parasite diversity, abundance and prevalence, but not parasite aggregation. In contrast, body size and gut size are positively related to aspects of parasite load within, but not between species. The influence of host phylogeny varies considerably among measures of parasite load, with the greatest influence exerted on parasite diversity. These results reveal that both host morphology and biotic interactions are key determinants of host–parasite associations and that consideration of multiple aspects of parasite load is required to fully understand patterns in parasitism.

不同宿主物种间的寄生虫多样性与丰度（统称寄生虫负荷（parasite load））差异极大。然而，宿主性状对寄生现象变异的影响仍未得到充分解析。过往针对寄生虫负荷的比较研究，大多仅考察了寄生虫物种丰富度指标，且主要基于已发表文献中的记录数据。因此，学界对于宿主性状与寄生虫负荷其他维度（如寄生虫丰度、感染率（prevalence）及聚集度（aggregation））之间的关联仍知之甚少。与此同时，从多独立来源整合数据的局限性，可能会干扰我们对寄生虫物种丰富度的认知。
本研究针对坦噶尼喀湖慈鲷鱼类及其携带的蠕虫寄生虫（helminth parasites）开展野外调查。我们采用贝叶斯系统发育比较框架（Bayesian phylogenetic comparative framework），检验了五种被认为可影响寄生现象的关键宿主性状——体型（body size）、肠长（gut length）、食性宽度（diet breadth）、生境复杂度（habitat complexity）以及同域宿主数量（sympatric hosts）——与多种寄生虫负荷指标之间的进化关联。
研究发现，特定宿主凭借其生境偏好可能接触到的宿主物种数量，是影响寄生虫多样性、丰度与感染率的普遍重要因素，但对寄生虫聚集度并无显著作用。与之相反，体型与肠大小仅与物种内的寄生虫负荷维度呈正相关，而在物种间则无此关联。宿主系统发育对寄生虫负荷各指标的影响差异显著，其中对寄生虫多样性的影响最为突出。
本研究结果表明，宿主形态与生物相互作用均是调控宿主-寄生虫互作关系（host–parasite associations）的关键因素，且只有综合考量寄生虫负荷的多个维度，才能全面解析寄生现象的分布格局。