Distance-decay differs among vertical strata in a tropical rainforest

Area of Science:

• Ecology
• Biodiversity Science
• Zoology

Background:

• The distance-decay relationship, where species similarity decreases with geographic distance, is a fundamental ecological pattern.
• Previous studies have explored distance-decay across various ecosystems and organisms, but its variation across forest vertical strata remains poorly understood.
• Understanding how forest stratification influences biodiversity patterns is crucial for comprehensive ecological assessments.

Purpose of the Study:

• To investigate the influence of ground versus arboreal amphibian assemblages on the general forest distance-decay relationship.
• To explain differences in distance-decay relationships between forest strata based on vertical stratification of composition, richness, and abundance.
• To determine if biodiversity patterns in horizontal space are consistent across vertical forest space.

Main Methods:

• Surveyed amphibians across vertical rainforest strata (ground, understory, canopy) in Madagascar.
• Defined species assemblages for ground-dwelling, understory, and canopy strata for each tree.
• Calculated horizontal distance-decay in similarity across all trees and within each forest stratum.

Main Results:

• Within-stratum comparisons revealed a classic distance-decay relationship for canopy and understory amphibian communities.
• No significant distance-decay relationship was observed for ground amphibian communities.
• The above-ground amphibian assemblage was identified as the primary driver of the classical distance-decay relationship in tropical rainforests.

Conclusions:

• Biodiversity patterns in horizontal space are not consistent across vertical forest strata.
• Canopy amphibian assemblages may follow different ecological rules compared to ground-dwelling conspecifics.
• Local habitat heterogeneity and arboreal traits likely influence dispersal and distribution, leading to variations in distance-decay relationships across strata.