Geographic barriers, such as mountain ranges, impede genetic exchange among populations, promoting diversification and speciation. The effectiveness of these barriers in limiting gene flow varies between lineages due to each species’ unique dispersal modes and capacities. Our understanding of how the Andes orogeny contributes to species diversification comes from well-studied vertebrates and a few insects, neglecting organisms unable to fly or walk long distances. Additionally, although the Andean altitude is usually assumed to be the driver of diversification, it is not often formally tested. This limits our understanding of how landscape changes, particularly altitude, influence population structure. Some arachnids, such as the colorful spider Gasteracantha cancriformis have been hypothesized to disperse long distances via ballooning (i.e., using their silk to interact with the wind). Still, we do not know how the environment and geography shape its genetic diversity. To address this question, we sampled thousands of loci across the distribution of this spider 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 elevation along the Andes, which decreases in some regions, facilitating cross-Andean dispersal and gene flow. Our findings support that elevation in the Andes plays a major role in structuring populations in South America, but the strength of this barrier can be defeated by organisms with long-distance dispersal modes together with altitudinal depressions

Paramos are a unique type of tropical alpine ecosystem. To understand how biodiversity, ecosystem services and community resilience in the paramo will be affected by ongoing environmental change we need to start identifying groups of species with shared characteristics (i.e. functional types or PFTs). This task is particularly challenging as paramos host the highest plant diversity of alpine ecosystems. We measured 22 traits on 42 species belonging to different growth forms in the Colombian Andes. Hierarchical Clustering on Principal Components performed in a Factor analysis of mixed data was used to identify species with similar functional traits and the number of PFTs present. We identified three PFTs; one composed of forbs and shrubs with tender leaves, one composed of only rosettes, and a third group composed by shrubs with tough leaves. If PFTs represent a group of plants that play similar roles in the ecosystem, and have similar responses to perturbation, our results imply that paramos might have limited physiological response and may be highly vulnerable to environmental changes. On the other hand, the presence of multiple species sharing functional traits could provide some resilience, if one species disappears, others may fill the same role and maintain the functionality of the paramo.