Resolving the Context-Dependency of Local Heterogeneity-Diversity Relationships across Rocky Reefs WorldwideMacroecology

Jordi Sola¹, John Griffin²

¹King Abdullah University of Science and Technology, Saudi Arabia - ²Swansea University, UK

Environmental heterogeneity is widely hypothesized to enhance biodiversity, but significant variability in this relationship has limited its predictive utility. To resolve this context-dependency, we developed a common framework synthesising global literature and identified key factors or moderators driving these patterns. Heterogeneity, defined as spatial variability within a given area, was classified into facets based on proxies such as three-dimensional structure (e.g., substrate rugosity), complexity (e.g., fractal dimension), and feature variability (e.g., mussel size classes). Analyzing data from 144 rocky reef studies (over 3,000 effects), we found that all heterogeneity facets positively influenced biodiversity. Among these, three-dimensional structures had the strongest impact, likely due to enhanced niche provision and increased substrate area. Responses varied by organismal traits, with small-bodied and swimming species benefitting most, while larger-bodied benthic species exhibited weaker responses. Environmental moderators further shaped these effects, with biogenic substrates and stressful conditions—particularly in intertidal zones and equatorial regions—amplifying biodiversity gains. Our findings reveal that the effects of heterogeneity on biodiversity are context-dependent, driven by heterogeneity facets, organismal traits, and environmental stressors. This refined understanding enables more accurate predictions of biodiversity patterns and highlights where and how heterogeneity can most effectively promote biodiversity, resilience and functioning.