LB 4-34 - CANCELLED - Macro-organism biodiversity mediates micro-organism biodiversity on tropical Pacific coral reefs

Interactions between diverse microbes and macro-organisms (or macrobes) underpin important biosphere processes, yet our understanding of what controls this biodiversity is artificially divided between microbes and macrobes. Established drivers of macrobial diversity (e.g., isolation and area) translate inconsistently to microbes. However, limited attempts to make this translation have not accounted for how microbe-macrobe interactions may result in drivers influencing microbial diversity indirectly, via their influence on macrobial diversity. To identify the drivers of microbial and macrobial biodiversity we applied a structural equation model – model selection approach to multi-gene metabarcoding data from Pacific coral reefs. Our results suggest that, contrary to expectations, isolation, area and anthropogenic stress have weak direct effects on microbial biodiversity and mainly act indirectly via their effects on macrobial biodiversity. We suggest that decreasing macrobial biodiversity decreases the niches available to microbes, which results in decreased microbial biodiversity and may have implications for how ecosystems respond to and recover from environmental change.