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.

在时空维度上发生的地理范围扩张与隔离事件，为寄生虫提供了拓展宿主范围的契机，此类事件与宿主-寄生虫镶嵌组合体（host-parasite mosaic assemblages）的形成以及寄生虫的物种分化密切相关。本研究以加那利群岛（Canary Islands）中隶属于Spauligodon属的宿主特异性寄生线虫类群为研究对象，探讨岛屿定殖事件是否会引发宿主范围的波动。本研究进一步探究了宿主范围波动是否会如岛屿寄生虫的预期那样，引发宿主广度（host breadth）的改变，即宿主专化性。研究基于分子数据，采用贝叶斯法（Bayesian methods）推断了寄生虫的系统发育关系与分化时间估算值；先通过全局拟合方法（global-fit method）进行先验评估，筛选出可能代表共分化关联的宿主-寄生虫配对，随后以宿主分化时间作为校准先验（calibration priors）。随后重建了寄生虫的定殖历史，并对宿主范围波动事件与宿主专化性水平进行了估算。研究结果显示，加那利群岛中存在4个Spauligodon演化支（clades），其起源至少涉及3次独立的定殖事件。本研究发现了寄生虫向全新宿主发生宿主范围波动的证据，其中一次波动事件甚至推动了更高程度的物种分化。当前的宿主-寄生虫关联呈现出极强的宿主专化性，这表明宿主广度的改变仅发生在宿主范围波动的阶段。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分化过程中，其宿主范围波动的幅度也更大。本研究结果表明，一个演化支的进化历史或许是预测寄生虫未来宿主范围扩张潜力的最佳指标。