Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI 53706, USA.
Department of Biology, Western Connecticut State University, 181 White Street, Danbury, CT 06810, USA.
Syst Biol. 2022 Oct 12;71(6):1281-1289. doi: 10.1093/sysbio/syac021.
Scorpions constitute a charismatic lineage of arthropods and comprise more than 2500 described species. Found throughout various tropical and temperate habitats, these predatory arachnids have a long evolutionary history, with a fossil record that began in the Silurian. While all scorpions are venomous, the asymmetrically diverse family Buthidae harbors nearly half the diversity of extant scorpions, and all but one of the 58 species that are medically significant to humans. However, the lack of a densely sampled scorpion phylogeny has hindered broader inferences of the diversification dynamics of scorpion toxins. To redress this gap, we assembled a phylogenomic data set of 100 scorpion venom gland transcriptomes and genomes, emphasizing the sampling of highly toxic buthid genera. To infer divergence times of venom gene families, we applied a phylogenomic node dating approach for the species tree in tandem with phylostratigraphic bracketing to estimate the minimum ages of mammal-specific toxins. Our analyses establish a robustly supported phylogeny of scorpions, particularly with regard to relationships between medically significant taxa. Analysis of venom gene families shows that mammal-active sodium channel toxins (NaTx) have independently evolved in five lineages within Buthidae. Temporal windows of mammal-targeting toxin origins are correlated with the basal diversification of major scorpion mammal predators such as shrews, bats, and rodents. These results suggest an evolutionary model of relatively recent diversification of buthid NaTx homologs in response to the diversification of scorpion predators. [Adaptation; arachnids; phylogenomic dating; phylostratigraphy; venom.].
蝎子是一种具有魅力的节肢动物谱系，包含超过 2500 种已描述的物种。这些掠食性蛛形纲动物分布在各种热带和温带栖息地，具有悠久的进化历史，化石记录始于志留纪。虽然所有蝎子都有毒，但不对称多样化的 Buthidae 家族拥有现存蝎子的近一半多样性，以及对人类具有医学意义的 58 种蝎子中的除一种之外的所有物种。然而，由于缺乏对蝎子系统发育进行密集采样，因此阻碍了对蝎子毒素多样化动态的更广泛推断。为了解决这一差距，我们组装了一个由 100 个蝎子毒液腺转录组和基因组组成的基因组数据集，重点对高度有毒的 Buthidae 属进行采样。为了推断毒液基因家族的分歧时间，我们应用了一种基因组节点约会方法来推断物种树，同时结合系统发生学框定来估计哺乳动物特异性毒素的最小年龄。我们的分析建立了一个强有力的蝎子系统发育，特别是在与具有医学意义的分类群的关系方面。毒液基因家族的分析表明，哺乳动物活性钠离子通道毒素 (NaTx) 在 Buthidae 内的五个谱系中独立进化。哺乳动物靶向毒素起源的时间窗口与主要蝎子哺乳动物捕食者（如鼩鼱、蝙蝠和啮齿动物）的基础多样化相关。这些结果表明，在捕食者蝎子多样化的相对较近的时间内，Buthidae NaTx 同源物发生了多样化的进化模型。[适应；蛛形纲动物；系统发生年代测定；系统发生地层学；毒液。]
