Amblyomma is the third most diversified genus of Ixodidae that is distributed across the Indomalayan, Afrotropical, Australasian (IAA), Nearctic and Neotropical biogeographic ecoregions, reaching in the Neotropic its highest diversity. There have been hints in previously published phylogenetic trees from mitochondrial genome, nuclear rRNA, from combinations of both and morphology that the Australasian Amblyomma or the Australasian Amblyomma plus the Amblyomma species from the southern cone of South America, might be sister-group to the Amblyomma of the rest of the world. However, a stable phylogenetic framework of Amblyomma for a better understanding of the biogeographic patterns underpinning its diversification is lacking. We used genomic techniques to sequence complete and nearly complete mitochondrial genomes –ca. 15 kbp– as well as the nuclear ribosomal cluster –ca. 8 kbp– for 17 Amblyomma ticks in order to study the phylogeny and biogeographic pattern of the genus Amblyomma, with particular emphasis on the Neotropical region. The new genomic information generated here together with genomic information available on 43 ticks (22 other Amblyomma species and 21 other hard ticks–as outgroup–) were used to perform probabilistic methods of phylogenetic and biogeographic inferences and time-tree estimation using biogeographic dates. In the present paper, we present the strongest evidence yet that Australasian Amblyomma may indeed be the sister-group to the Amblyomma of the rest of the world (species that occur mainly in the Neotropical and Afrotropical zoogeographic regions). Our results showed that all Amblyomma subgenera (Cernyomma, Anastosiella, Xiphiastor, Adenopleura, Aponomma and Dermiomma) are not monophyletic, except for Walkeriana and Amblyomma. Likewise, our best biogeographic scenario supports the origin of Amblyomma and its posterior diversification in the southern hemisphere at 47.8 and 36.8 Mya, respectively. This diversification could be associated with the end of the connection of Australasia and Neotropical ecoregions by the Antarctic land bridge. Also, the biogeographic analyses let us see the colonization patterns of some neotropical Amblyomma species to the Nearctic. We found strong evidence that the main theater of diversification of Amblyomma was the southern hemisphere, potentially driven by the Antarctic Bridge's intermittent connection in the late Eocene. In addition, the subgeneric classification of Amblyomma lacks evolutionary support. Future studies using denser taxonomic sampling may lead to new findings on the phylogenetic relationships and biogeographic history of Amblyomma genus.

中文翻译：

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基于丝裂基因组和核序列对 Amblyomma 蜱（螨：蜱科）的分子系统发育、生物地理学历史和多样化的新见解

Amblyomma 是蜱科第三个最多样化的属，分布在印度马拉雅、非洲热带、澳大利亚 (IAA)、近北冰洋和新热带生物地理生态区，在新热带地区达到了最高的多样性。之前发表的线粒体基因组、核 rRNA、两者组合和形态学的系统发育树中已经暗示，澳大利亚 Amblyomma 或澳大利亚 Amblyomma 加上来自南美洲南锥体的 Amblyomma 物种，可能是 Amblyomma 的姐妹群世界其他地区。然而，缺乏一个稳定的 Amblyomma 系统发育框架，以便更好地理解支撑其多样化的生物地理模式。我们使用基因组技术对完整和接近完整的线粒体基因组进行了测序 - 大约。15 kbp – 以及核核糖体簇 – ca。8 kbp – 用于 17 个 Amblyomma 蜱，以研究 Amblyomma 属的系统发育和生物地理模式，特别强调新热带地区。这里生成的新基因组信息与 43 种蜱虫（22 种其他 Amblyomma 物种和 21 种其他硬蜱——作为外群——）的基因组信息一起用于执行系统发育和生物地理推断的概率方法以及使用生物地理日期的时间树估计。在本文中，我们提出了迄今为止最有力的证据，表明澳大利亚Amblyomma确实可能是世界其他地区Amblyomma（主要出现在新热带和非洲热带动物地理区域的物种）的姐妹群。我们的结果表明，除了 Walkeriana 和 Amblyomma 之外，所有 Amblyomma 亚属（Cernyomma、Anastosiella、Xiphiastor、Aenopleura、Aponomma 和 Dermiomma）都不是单系的。同样，我们最好的生物地理情景支持 Amblyomma 的起源及其在南半球的后多样化，分别为 47.8 和 36.8 Mya。这种多样化可能与南极陆桥连接澳大利亚和新热带生态区的结束有关。此外，生物地理学分析让我们看到了一些新热带 Amblyomma 物种到近北极的殖民模式。我们发现强有力的证据表明，Amblyomma 多样化的主要区域是南半球，这可能是由始新世晚期南极桥间歇性连接所驱动的。此外，Amblyomma 的亚属分类缺乏进化支持。未来使用更密集的分类学采样的研究可能会对 Amblyomma 属的系统发育关系和生物地理学历史产生新的发现。