Scaling laws predict global microbial diversity

Abstract: Scaling laws underpin unifying theories of biodiversity and are among the most predictively powerful relationships in biology. However, scaling laws developed for plants and 8 animals often go untested or fail to hold for microorganisms. As a result, it is unclear whether scaling laws of biodiversity will span evolutionarily distant domains of life that encompass all 10 modes of metabolism and scales of abundance. Using a global-scale compilation of ~35,000 sites and ~5.6·106 species, including the largest ever inventory of high-throughput molecular data and 12 one of the largest compilations of plant and animal community data, we demonstrate similar rates of scaling in commonness and rarity across microorganisms and macroscopic plants and 14 animals. We document a universal dominance scaling law that holds across 30 orders of magnitude, an unprecedented expanse that predicts the abundance of dominant ocean bacteria. In 16 combining this scaling law with the lognormal model of biodiversity, we predict that Earth is home to upwards one trillion (1012) microbial species. Microbial biodiversity seems greater than 18 ever anticipated yet predictable from the smallest to the largest microbiome. 20 Significance statement: Ecological scaling laws are intensively studied for their predictiv