Data from: Whether larval amphibians school does not affect the parasite aggregation rule: testing the effects of host spatial heterogeneity in field and experimental studies

Almost all macroparasites show over-dispersed infections within natural host populations such that most parasites are distributed among a few heavily-infected individuals. Despite the importance of parasite aggregation for understanding system stability, the potential for population regulation, and super-spreading events, many questions persist about its underlying drivers. Theoretically, aggregation results from heterogeneity in host exposure, resistance, and tolerance. However, few studies have examined how host spatial arrangement – which likely affects both parasite encounter and density-dependent interactions – influences infection and dispersion, representing a critical gap in our current knowledge regarding the possible drivers of parasite aggregation. Using field data from over 165 ponds and 8,000 hosts, we evaluated how the spatial clustering of amphibian larvae within ponds 1) varied among different amphibian species, and 2), affected the distribution of parasites within the host population using Taylor’s Power Law. A complementary mesocosm experiment used field-guided manipulations of the spatial arrangement of larval amphibians to create a gradient in host clustering while controlling host density, thereby testing for spatial effects on both infection success and aggregation by three different trematode species. Our field data indicated that larval amphibians exhibited significant spatial clustering that was well captured by Taylor’s Power Law (R2 0.92 to 0.97 for different host species), but the residual variation only weakly correlated with observed patterns of trematode parasite over-dispersion. Correspondingly, experimental manipulation of host clustering had no effects on parasite infection success or the degree of parasite aggregation among cages or mesocosms. Given the importance of parasite over-dispersion for host populations and disease dynamics, we advocate for further investigations of host and parasite spatial aggregation, particularly studies that incorporate and/or control for heterogeneity in exposure and susceptibility.几乎所有大型寄生生物在自然宿主种群中均呈现过分散布（over-dispersed）的感染模式，即绝大多数寄生物仅分布于少数重度感染个体内。尽管寄生虫聚集现象对于理解生态系统稳定性、种群调控潜力以及超级传播事件均具有重要意义，但目前学界对其背后的驱动机制仍存在诸多未解之谜。从理论层面而言，寄生虫聚集源于宿主在暴露程度、抗性与耐受性上的异质性。然而，鲜有研究探讨宿主空间分布格局——这一因素可能同时影响寄生虫的宿主接触概率与密度依赖相互作用——如何作用于感染过程与寄生物分布，这一研究空白正是当前我们对寄生虫聚集驱动机制认知的关键短板。本研究依托覆盖165余个池塘与8000余只宿主的野外调查数据，借助泰勒幂法则（Taylor’s Power Law），探究了两点：其一，池塘内两栖类幼体的空间聚集程度是否因物种而异；其二，该聚集程度如何影响宿主种群内的寄生物分布格局。本研究配套开展了一项中宇宙（mesocosm）模拟实验：基于野外实际场景调控两栖类幼体的空间分布格局，在控制宿主密度的前提下构建宿主聚集程度梯度，以此检验空间因素对三种不同吸虫（trematode）的感染成功率与寄生聚集程度的影响。野外调查数据显示，两栖类幼体存在显著的空间聚集现象，且该聚集程度可通过泰勒幂法则得到良好拟合（不同宿主物种的拟合R²介于0.92至0.97之间），但模型残差与观测到的吸虫过分散布模式仅存在微弱相关性。与之对应，对宿主聚集程度的实验调控并未在围隔或中宇宙实验中对寄生虫感染成功率或寄生聚集程度产生显著影响。鉴于寄生虫过分散布模式对于宿主种群与疾病传播动态的重要意义，本研究呼吁学界进一步开展宿主与寄生物空间聚集相关研究，尤其是纳入并/或控制暴露程度与易感性异质性的相关工作。