Aggregation of infective stages of parasites as an adaptation and its implications for the study of parasite-host interactions

The causes and consequences of aggregation among conspecifics have received much attention. For infecting macroparasites, causes include variation among hosts in susceptibility, and/or whether infective stages are aggregated in the environment. Here, we link these two phenomena and explore whether aggregation of infective stages in the environment is adaptive to parasites encountering host condition-linked defenses, and what effect such aggregations have for parasite-host interactions. Using simulation models, we show that parasite fitness is increased by aggregates attacking a host, particularly when investment into defenses is high. The fitness benefit of aggregation remains despite inclusion of factors that should curb the benefits of aggregation: namely, mortality of low condition hosts (those hosts expected to be most susceptible to parasitism) and costs of high coinfection. Using sample sizes common in studies, aggregation of infective stages reduces the likelihood of detecting h...

同种个体间聚集的成因与后果已受到学界广泛关注。对于寄生性大型寄生虫（macroparasites）而言，其聚集的成因包括宿主间易感性的差异，以及环境中感染期虫体是否呈现聚集分布。本研究将这两类现象加以关联，探讨环境中感染期虫体的聚集是否对寄生虫适应宿主条件相关防御策略具有适应性优势，以及此类聚集对寄生虫-宿主互作产生的影响。通过模拟模型，我们发现当宿主对防御的投入较高时，多虫体聚集攻击宿主可提升寄生虫的适合度。即便纳入可能抑制聚集收益的两类因素——即低条件宿主（这类宿主本应最易感染寄生虫）的死亡率，以及高共感染带来的成本——聚集带来的适合度优势依然得以保留。采用现有研究中常见的样本量开展分析，感染期虫体的聚集会降低检测到h...的可能性。