Aggregation of symbionts on hosts depends on interaction type and host traits

Symbionts tend to be aggregated on their hosts, such that few hosts harbor the majority of symbionts. This ubiquitous pattern can result from stochastic processes, but aggregation patterns may also depend on the type of host-symbiont interaction, plus traits that affect host exposure and susceptibility to symbionts. Untangling how aggregation patterns both within and among populations depend on stochastic processes, interaction type and host traits remains an outstanding challenge. Here, we address this challenge by using null models to compare aggregation patterns in a neutral system of Balanomorpha barnacles attached to patellid limpets and a host-parasite system of Trinidadian guppies (Poecilia reticulata) and their Gyrodactylus spp. monogeneans. We first used a model to predict patterns of symbiont-host aggregation due to random partitioning of symbionts to hosts. This null model accurately predicted the aggregation of barnacles on limpets, but the degree of aggregation varied acros...

共生体（symbionts）往往在宿主表面聚集，呈现出少数宿主承载绝大多数共生体的分布格局。这种广泛存在的模式既可由随机过程导致，也可能依赖于宿主-共生体互作类型，以及影响宿主暴露风险与共生体易感性的宿主性状。厘清种群内部与种群间的聚集格局如何受随机过程、互作类型及宿主性状的调控，仍是一项尚未解决的突出难题。本研究通过采用零模型（null models），对比分析了两类系统的聚集模式：一类是附着于帽贝科（patellid）帽螺的围胸目藤壶（Balanomorpha barnacles）中性系统，另一类是特立尼达孔雀鱼（孔雀花鳉，Poecilia reticulata）与其三代虫属（Gyrodactylus spp.）单殖吸虫（monogeneans）构成的宿主-寄生虫系统。我们首先构建了一个模型，用于预测因共生体随机分配至宿主而形成的宿主-共生体聚集格局。该零模型能够准确预测藤壶在帽螺上的聚集程度，但聚集强度随……