Local-scale dispersal constraints promote spatial structure and
arthropod diversity within a tropical sky-island
Abstract
Physical disruption of gene flow among mountains is commonly viewed as
an important process for the generation of hyperdiverse tropical
mountain biotas. However, the role of in situ diversification
within mountains has been seldom explored. Here we evaluate spatially
fine-scale patterns of arthropod community assembly within a single
mountain to understand the role of dispersal limitation and landscape
features as drivers of tropical mountain diversity. We focus on a single
tropical sky-island of the Transmexican Volcanic Belt, where we sampled
whole-communities of arthropods for eight orders with a comparable
design at a spatial scale ranging from 50 m to 20 km, using 840 pitfall
traps and whole community metabarcoding. We explored multiple
hierarchical levels, from individual haplotypes to lineages at 0.5, 1.5,
3, 5, 7.5% similarity thresholds, to evaluate patterns of richness,
turnover and distance decay of similarity with isolation-by-distance and
isolation-by-resistance approaches. Our results showed that distance and
altitude influence distance decay of similarity at all hierarchical
levels. This holds for arthropod groups of contrasting dispersal
abilities, but with different strength depending on the spatial scale.
Our results suggest long-term persistence of lineages within sky
islands, combined with local-scale differentiation, may be an important
driver of high arthropod biodiversity in tropical mountains.