Department of Biology, Faculty of Natural Sciences, Universidad del Rosario, Bogotá, Colombia.
School of BioSciences, The University of Melbourne, Parkville, Victoria, Australia.
Mol Ecol. 2024 Jun;33(11):e17361. doi: 10.1111/mec.17361. Epub 2024 Apr 18.
Geographical barriers like mountain ranges impede genetic exchange among populations, promoting diversification. The effectiveness of these barriers in limiting gene flow varies between lineages due to each species' dispersal modes and capacities. Our understanding of how the Andes orogeny contributes to species diversification comes from well-studied vertebrates and a few arthropods and plants, neglecting organisms unable to fly or walk long distances. Some arachnids, such as Gasteracantha cancriformis, have been hypothesized to disperse long distances via ballooning (i.e. using their silk to interact with the wind). Yet, we do not know how the environment and geography shape its genetic diversity. Therefore, we tested whether the Andes contributed to the diversification of G. cancriformis acting as an absolute or semi-permeable barrier to genetic connectivity between populations of this spider at opposite sides of the mountain range. We sampled thousands of loci across the distribution of the species and implemented population genetics, phylogenetic, and landscape genetic analyses. We identified two genetically distinct groups structured by the Central Andes, and a third less structured group in the Northern Andes that shares ancestry with the previous two. This structure is largely explained by the altitude along the Andes, which decreases in some regions, possibly facilitating cross-Andean dispersal and gene flow. Our findings support that altitude in the Andes plays a major role in structuring populations in South America, but the strength of this barrier can be overcome by organisms with long-distance dispersal modes together with altitudinal depressions.
地理障碍，如山脉，阻碍了种群之间的基因交流，促进了多样化。由于每个物种的扩散模式和能力不同，这些障碍在限制基因流动方面的有效性在不同的谱系之间有所不同。我们对安第斯造山运动如何促进物种多样化的理解来自于对脊椎动物和少数节肢动物和植物的深入研究，而忽略了那些无法远距离飞行或行走的生物。一些蛛形纲动物，如 Gasteracantha cancriformis，据推测可以通过气球（即利用它们的丝与风相互作用）远距离扩散。然而，我们不知道环境和地理如何塑造它的遗传多样性。因此，我们测试了安第斯山脉是否作为绝对或半渗透的屏障，对这种蜘蛛在山脉两侧种群之间的遗传连通性起到了作用，从而导致了 G. cancriformis 的多样化。我们在该物种的分布范围内采样了数千个基因座，并实施了种群遗传学、系统发育学和景观遗传学分析。我们确定了两个由中央安第斯山脉构成的遗传上截然不同的群体，以及第三个在北安第斯山脉的遗传结构不太明显的群体，该群体与前两个群体有共同的祖先。这种结构在很大程度上可以用安第斯山脉的海拔来解释，在某些地区，海拔会降低，这可能促进了跨安第斯山脉的扩散和基因流动。我们的研究结果表明，安第斯山脉的海拔在南美洲的种群结构中起着重要作用，但具有远距离扩散模式的生物以及海拔下降可以克服这种屏障的强度。
