Data from: Ecological host fitting of Trypanosoma cruzi TcI in Bolivia: mosaic population structure, hybridization and a role for humans in Andean parasite dispersal

An improved understanding of how a parasite species exploits its genetic repertoire to colonize novel hosts and environmental niches is crucial to establish the epidemiological risk associated with emergent pathogenic genotypes. Trypanosoma cruzi, a genetically heterogeneous, multi-host zoonosis, provides an ideal system to examine the sylvatic diversification of parasitic protozoa. In Bolivia, T. cruzi I, the oldest and most widespread genetic lineage, is pervasive across a range of ecological clines. High-resolution nuclear (26 loci) and mitochondrial (10 loci) genotyping of 199 contemporaneous sylvatic TcI clones was undertaken to provide insights into the biogeographical basis of T. cruzi evolution. Three distinct sylvatic parasite transmission cycles were identified: one highland population among terrestrial rodent and triatomine species, composed of genetically homogenous strains (Ar = 2.95; PA/L = 0.61; DAS = 0.151), and two highly diverse, parasite assemblages circulating among predominantly arboreal mammals and vectors in the lowlands (Ar = 3.40 and 3.93; PA/L = 1.12 and 0.60; DAS = 0.425 and 0.311, respectively). Very limited gene flow between neighbouring terrestrial highland and arboreal lowland areas (distance ~220 km; FST = 0.42 and 0.35) but strong connectivity between ecologically similar but geographically disparate terrestrial highland ecotopes (distance >465 km; FST = 0.016–0.084) strongly supports ecological host fitting as the predominant mechanism of parasite diversification. Dissimilar heterozygosity estimates (excess in highlands, deficit in lowlands) and mitochondrial introgression among lowland strains may indicate fundamental differences in mating strategies between populations. Finally, accelerated parasite dissemination between densely populated, highland areas, compared to uninhabited lowland foci, likely reflects passive, long-range anthroponotic dispersal. The impact of humans on the risk of epizootic Chagas disease transmission in Bolivia is discussed.深入解析寄生虫物种如何利用其遗传基因库侵染新型宿主与生态位，对于明确新兴致病基因型相关的流行病学风险至关重要。克氏锥虫（Trypanosoma cruzi）是一种遗传异质性的多宿主人畜共患病原，是研究寄生原虫野外演化分化的理想模型系统。在玻利维亚境内，作为最古老且分布最广的遗传谱系的克氏锥虫I型（TcI）广泛存在于多种生态梯度中。本研究对199株同期野生TcI克隆株开展了高分辨率核基因（26个位点）与线粒体基因（10个位点）分型，以解析克氏锥虫演化的生物地理学基础。研究共鉴定出3种独立的野生寄生虫传播循环：其一为高地种群，分布于陆生啮齿类与锥蝽（triatomine）物种之间，由遗传均一的虫株构成（Ar = 2.95; PA/L = 0.61; DAS = 0.151）；另外两种为高度多样化的寄生虫类群，主要在低地的树栖哺乳动物及其传播媒介间循环流行，其对应参数分别为Ar = 3.40和3.93、PA/L = 1.12和0.60、DAS = 0.425和0.311。相邻陆地高地与树栖低地生境（距离约220 km; FST = 0.42和0.35）间的基因交流极度有限，而生态特征相似但地理分隔遥远的陆地高地生态小区（距离＞465 km; FST = 0.016–0.084）间却存在强连通性，这一结果强烈支持生态宿主适配作为寄生虫分化的主要驱动机制。不同种群的杂合度估计值存在显著差异（高地种群杂合过剩，低地种群杂合缺失），且低地虫株间存在线粒体基因渐渗现象，这可能表明不同种群间的交配策略存在根本性差异。最后，相较于无人定居的低地疫源地，人口稠密的高地区域间的寄生虫扩散速度更快，这大概率反映了寄生虫经人类活动实现的被动长距离扩散。本文讨论了人类活动对玻利维亚境内恰加斯病（Chagas disease）兽疫传播风险的影响。