Data from: Getting there and around: host range oscillations during colonisation of the Canary Islands by the parasitic nematode Spauligodon

Episodes of expansion and isolation in geographic range over space and time, during which parasites have the opportunity to expand their host range, are linked to the development of host-parasite mosaic assemblages and parasite diversification. In this study we investigated whether island colonisation events lead to host range oscillations in a taxon of host-specific parasitic nematodes of the genus Spauligodon in the Canary Islands. We further investigated if range oscillations also resulted in shifts in host breadth (i.e. specialization), as expected for parasites on islands. Parasite phylogeny and divergence time estimates were inferred from molecular data with Bayesian methods. Host divergence times were set as calibration priors after a priori evaluation with a global-fit method of which individual host-parasite associations likely represent cospeciation links. Parasite colonisation history was reconstructed, followed by an estimation of oscillation events and specificity level. The results indicate the presence of four Spauligodon clades in the Canary Islands, which originated from at least three different colonisation events. We found evidence of host range oscillations to truly novel hosts, which in one case led to higher diversification. Contemporary host-parasite associations show strong host specificity, suggesting that changes in host breadth were limited to the shift period. Lineages with more frequent and wider taxonomic host range oscillations prior to the initial colonisation event showed wider range oscillations during colonisation and diversification within the archipelago. Our results suggest that a lineage’s evolutionary past may be the best indicator of a parasite’s potential for future range expansions.寄生虫的地理分布范围在时空维度上反复经历扩张与隔离事件，在此期间寄生虫有机会拓展宿主范围，这一过程与宿主-寄生虫镶嵌组合（host-parasite mosaic assemblages）的形成以及寄生虫的物种多样化密切相关。本研究以加那利群岛（Canary Islands）中隶属于斯氏线虫属（Spauligodon）的一类宿主特异性寄生线虫类群为研究对象，探究岛屿定殖事件是否会引发宿主范围波动。本研究进一步考察了分布范围波动是否会如岛屿寄生虫的理论预期那般，引发宿主广度（即宿主特化程度）的转变。研究人员通过贝叶斯方法（Bayesian methods）分析分子数据，重建了寄生线虫的系统发育关系并估算其分化时间；在通过全局拟合方法（global-fit method）预先评估哪些宿主-寄生虫关联可能代表共成种关联（cospeciation links）后，将宿主分化时间设置为校准先验（calibration priors）。随后重建了寄生虫的定殖历史，并估算了其分布范围波动事件与宿主特异性水平。研究结果显示，加那利群岛中共存在4个斯氏线虫属（Spauligodon）演化支，其起源至少涉及3次独立的定殖事件。研究发现了寄生虫向全新宿主拓展宿主范围的波动证据，其中一次波动事件进一步推动了更高程度的物种多样化。当前的宿主-寄生虫关联呈现出极强的宿主特异性，这表明宿主广度的变化仅局限于波动发生的时期。在初始定殖事件前，分类学宿主范围波动更频繁、幅度更广的演化支，在群岛内的定殖与物种多样化过程中，其宿主范围波动幅度也更大。本研究结果表明，演化支的进化历史或许是预测寄生虫未来分布范围扩张潜力的最佳指标。