The Andes as a semi‐permeable geographical barrier: Genetic connectivity between structured populations in a widespread spider

• Published in: Molecular ecology 2024-06, Vol.33 (11), p.e17361-n/a
• Main Authors: Salgado‐Roa, Fabian C., Pardo‐Diaz, Carolina, Rueda‐M, Nicol, Cisneros‐Heredia, Diego F., Lasso, Eloisa, Salazar, Camilo
• Format: Article
• Language: English
• Subjects: Altitude; arachnid; Arthropods; colour polymorphism; Dispersal; Gene flow; Genetic analysis; Genetic diversity; Genetics; Geographical distribution; Geography; Mountains; Orogeny; Permeability; Phylogeny; phylogeography; Population genetics; Populations; Spiders; Vertebrates
• ISSN: 0962-1083; 1365-294X
• DOI: 10.1111/mec.17361

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. Resumen Las barreras geográficas como las cordilleras montañosas impiden el intercambio genético entre poblaciones, promoviendo la diversificación. La efectividad de estas barreras para limitar el flujo genético varía entre linajes debido a los modos y capacidades de dispersión de cada especie. Nuestra comprensión de cómo la orogenia de los Andes contribuye a la diversificación de especies proviene de vertebrados y algunos artrópodos y plantas bien estudiados, descuidando a los organismos incapaces de volar o caminar grandes distancias. Se ha hipotetizado que algunas arañas, como Gasteracantha cancriformis, se dispersan a grandes distancias mediante la técnica de “ballooning” (es decir, utilizando su seda para interactuar con el viento). Sin embargo, no sabemos cómo el entorno y la geografía han dad