Department of Zoology, National Museum, Cirkusová 1740, Prague, Czech Republic; Department of Zoology, Faculty of Science, Charles University, Viničná 7, Prague, Czech Republic.
Department of Zoology, National Museum, Cirkusová 1740, Prague, Czech Republic; Department of Zoology, Faculty of Science, Charles University, Viničná 7, Prague, Czech Republic.
Mol Phylogenet Evol. 2021 Feb;155:107012. doi: 10.1016/j.ympev.2020.107012. Epub 2020 Nov 18.
Large parts of the Sahara Desert and Arabia are covered by sand seas and sand dunes, which are inhabited by specialized animal communities. For example, many lizards have developed adaptations to life in loose sand, including sand-swimming behavior. The best-known sand swimmers of the Saharo-Arabia are the sandfish skinks (genus Scincus). Although there are currently only four Scincus species recognized, their phylogenetic relationships have not yet been addressed in detail. We use eight genetic markers (three mitochondrial, five nuclear) and a complete sampling of species to infer the relationships within the genus. We employ multiple phylogenetic approaches to reconstruct the evolutionary history of these skinks and to assess the level of reticulation at the onset of their radiation. Our results indicate the presence of five strongly supported species-level lineages, four represented by the currently recognized species and the fifth by S. scincus conirostris, which does not form a clade with S. scincus. Based on these results we elevate the Iranian and northern Arabian S. conirostris to the species level. The two Saharan species, S. albifasciatus and S. scincus, are sister in all analyses. Deeper relationships within the genus, however, remained largely unresolved despite the extensive genetic data set. This basal polytomy, together with the fact that we detected no sign of hybridization in the history of the genus, indicates that the diversification of the five Scincus species was rapid, burst-like, and not followed by secondary hybridization events. Divergence time estimations show a Middle Pliocene crown radiation of the genus (3.3 Mya). We hypothesize that the aridification of the Saharo-Arabia that began in the Late Miocene triggered the initial diversification of Scincus, and that the subsequent expansion of sand deserts enabled their dispersal over the large Saharan and Arabian range. We discuss the evolution of body form in sand swimming lizards and ponder how Scincus retained their fully limbed morphology despite being sand swimmers that are typically limbless.
撒哈拉沙漠和阿拉伯地区的大部分地区都被沙海和沙丘覆盖，这些地区栖息着专门的动物群落。例如，许多蜥蜴已经适应了松散的沙子生活，包括沙泳行为。撒哈拉-阿拉伯地区最著名的沙泳蜥蜴是沙鱼蜥蜴（Scincus 属）。虽然目前只识别出四个 Scincus 物种，但它们的系统发育关系尚未详细解决。我们使用了八个遗传标记（三个线粒体，五个核）和完整的物种样本来推断属内的关系。我们采用多种系统发育方法来重建这些蜥蜴的进化历史，并评估它们辐射开始时的网状程度。我们的研究结果表明，存在五个强烈支持的种级谱系，其中四个由目前公认的物种代表，第五个由 S. scincus conirostris 代表，它与 S. scincus 没有形成一个分支。基于这些结果，我们将伊朗和北部阿拉伯的 S. conirostris 提升为物种水平。所有分析中，两种撒哈拉蜥蜴 S. albifasciatus 和 S. scincus 都是姐妹种。然而，属内更深层次的关系在很大程度上仍然没有得到解决，尽管有广泛的遗传数据集。这种基本的多系现象，以及我们在属的历史中没有发现杂交迹象的事实，表明五个 Scincus 物种的多样化是快速的、爆发式的，并且没有发生二次杂交事件。分化时间估计表明，该属在中新世中期出现了一个冠辐射（330 万年前）。我们假设，中新世晚期开始的撒哈拉-阿拉伯地区的干旱化引发了 Scincus 的最初多样化，随后沙丘沙漠的扩张使它们能够在撒哈拉和阿拉伯大范围内扩散。我们讨论了沙泳蜥蜴的身体形态进化，并思考了 Scincus 如何在保持四肢完全形态的情况下成为沙泳蜥蜴。
