Data from: Distance-decay differs among vertical strata in a tropical rainforest

1. Assemblage similarity decays with geographic distance—a pattern known
as the distance-decay relationship. While this pattern has been
investigated for a wide range of organisms, ecosystems, and geographical
gradients, whether these changes vary more cryptically across different
forest strata (from ground to canopy) remains elusive. 2. Here, we
investigated the influence of ground vs arboreal assemblages to the
general distance-decay relationship observed in forests. We seek to
explain differences in distance-decay relationships between strata in the
context of the vertical stratification of assemblage composition,
richness, and abundance. 3. We surveyed for a climate sensitive model
organism, amphibians, across vertical rainforest strata in Madagascar. For
each tree, we defined assemblages of ground-dwelling, understory, or
canopy species. We calculated horizontal distance-decay in similarity
across all trees, and across assemblages of species found in different
forest strata (ground, understory, and canopy). 4. We demonstrate that
within stratum comparisons exhibit a classic distance-decay relationship
for canopy and understory communities but no distance-decay relationships
for ground communities. We suggest that differences in horizontal turnover
between strata may be due to local scale habitat and resource
heterogeneity in the canopy, or the influence of arboreal traits on
species dispersal and distribution. 5. Synthesis: Biodiversity patterns in
horizontal space were not consistent across vertical space, suggesting
that canopy fauna may not play by the same set of ‘rules’ as their
conspecifics living below them on the ground. Our study provides
compelling evidence that the above-ground amphibian assemblage of tropical
rainforests is the primary driver of the classical distance-decay
relationship.