Distribution of ant assemblage, microclimate and microhabitat along vertical gradients

Abiotic and biotic factors structure species assembly in ecosystems both
horizontally and vertically. However, the way community composition
changes along comparable horizontal and vertical distances in complex
three-dimensional habitats, and the factors driving these patterns,
remains poorly understood. By sampling ant assemblages at comparable
vertical and horizontal spatial scales in a tropical rain forest, we
tested hypotheses that predicted differences in vertical and horizontal
turnover explained by different drivers in vertical and horizontal space.
These drivers included environmental filtering, such as microclimate
(temperature, humidity, and photosynthetic photon flux density) and
microhabitat connectivity (leaf area) which are structured differently
across vertical and horizontal space. We found that both ant abundance and
richness decreased significantly with increasing vertical height. Although
dissimilarity between ant assemblages increased with vertical distance,
indicating a clear distance-decay pattern, the dissimilarity was higher
horizontally where it appeared independent of distance. The pronounced
horizontal and vertical structuring of ant assemblages across short
distances is likely explained by a combination of microclimate and
microhabitat connectivity. Our results demonstrate the importance of
considering three-dimensional spatial variation in local assemblages and
reveal how highly diverse communities can be supported by complex
habitats.