In parasites that strongly rely on a host for dispersal, geographic barriers that act on the host will simultaneously influence parasite distribution as well. If their association persists over macroevolutionary time it may result in congruent phylogenetic and phylogeographic patterns due to shared geographic histories. Here, we investigated the level of congruent evolutionary history at a regional and global scale in a highly specialised parasite taxon infecting hosts with limited dispersal abilities: the microsporidians Dictyocoela spp. and their amphipod hosts. Dictyocoela can be transmitted both vertically and horizontally and is the most common microsporidian genus occurring in amphipods in Eurasia. However, little is known about its distribution elsewhere. We started by conducting molecular screening to detect microsporidian parasites in endemic amphipod species in New Zealand; based on phylogenetic analyses, we identified nine species‐level microsporidian taxa including six belonging to Dictyocoela. With a distance‐based cophylogenetic analysis at the regional scale, we identified overall congruent phylogenies between Paracalliope, the most common New Zealand freshwater amphipod taxon, and their Dictyocoela parasites. Also, hosts and parasites showed similar phylogeographic patterns suggesting shared biogeographic histories. Similarly, at a global scale, phylogenies of amphipod hosts and their Dictyocoela parasites showed broadly congruent phylogenies. The observed patterns may have resulted from covicariance and/or codispersal, suggesting that the intimate association between amphipods and Dictyocoela may have persisted over macroevolutionary time. We highlight that shared biogeographic histories could play a role in the codiversification of hosts and parasites at a macroevolutionary scale.

中文翻译：

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共享的地理历史和散布有助于两栖动物及其微孢子虫寄生虫在区域和全球范围内的一致系统发育。

在强烈依赖宿主传播的寄生虫中，作用于宿主的地理障碍也会同时影响寄生虫的分布。如果它们的关联在宏观进化时期内持续存在，由于共同的地理历史，可能会导致系统发育和系统地理学模式的一致性。在这里，我们在高度专业化的寄生虫分类群中研究了区域和全球范围内一致进化史的水平，这些寄生虫感染了传播能力有限的宿主：微孢子虫Dictyocoela spp。和他们的两栖动物宿主。梭菌可以垂直和水平传播，是欧亚大陆两栖动物中最常见的微孢子虫属。但是，对其分布在其他地方知之甚少。我们从进行分子筛查开始，以检测新西兰地方性两栖动物物种中的微孢子虫寄生虫；根据系统发育分析，我们确定了9种物种级的微孢子虫类群，其中6种属于小核藻。在区域尺度基于距离的cophylogenetic分析，我们确定了整体之间的系统发育一致Paracalliope，最常见的新西兰淡水足目类群，它们Dictyocoela寄生虫。同样，寄主和寄生虫也表现出相似的系统地理学模式，这表明它们具有共同的生物地理历史。同样，在全球范围内，两栖动物宿主及其双壁梭菌寄生虫的系统发育显示出广泛一致的系统发育。所观察到的图案可以导致从covicariance和/或codispersal，表明片脚之间的紧密缔合Dictyocoela可以具有优于宏观进化时间持续。我们着重指出，共享的生物地理历史可以在宏观进化规模的宿主和寄生虫的共生化中发挥作用。