Abstract. Macroecology seeks to understand broad-scale patterns in the diversity and abundance of organisms, but macroecologists typically study aboveground macroorganisms. Belowground organisms regulate numerous ecosystem functions, yet we lack understanding of what drives their diversity. Here, we examine the controls on belowground diversity along latitudinal and elevational gradients. We performed a global meta-analysis of 325 soil communities across 20 studies conducted along temperature and soil pH gradients. Belowground taxa, whether bacterial or fungal, observed along a given gradient of temperature or soil pH were equally likely to show a linear increase, linear decrease, humped pattern, trough-shaped pattern, or no pattern in diversity along the gradient. Land-use intensity weakly affected the diversity-temperature relationship, but no other factor did so. Our study highlights disparities among diversity patterns of soil microbial communities. Belowground diversity may be controlled by the associated climatic and historical contexts of particular gradients, by factors not typically measured in community-level studies, or by processes operating at scales that do not match the temporal and spatial scales under study. Because these organisms are responsible for a suite of key processes, understanding the drivers of their distribution and diversity is fundamental to understanding the functioning of ecosystems.

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AimBiomes, biogeographical realms and ecoregions have become central concepts of biotic organization and biodiversity research. Recent data‐intensive analysis has shown that, while ecoregions do delineate biotic communities, how distinct they are from one another varies considerably across regions and taxa. Given their central importance to global models of the earth system and to the development of conservation plans, it is key to understand in what regions, and for which taxa, ecoregion classification schemes best describe the underlying variability in biological communities.LocationGlobal.TaxaPlants, animals, fungi.MethodsIn this paper, we integrate ecoregion maps with data on spatially continuous changes in environmental conditions, biodiversity and species traits to quantify the descriptive power of ecoregions around the globe. Capitalizing on the troves of newly available global biodiversity data, we model the abiotic and biotic factors that describe how distinct ecoregions are from one another.ResultsFrom an abiotic perspective, we report compelling evidence that, first, ecoregions are more distinct in tropical zones with higher temperatures, less temperature seasonality and greater rainfall seasonality. Second, we also find that ecoregions are more distinct in regions with steeper slopes. From a biotic perspective, we find that ecoregions tend to be more distinct for reptiles and amphibians than they are for mammals or birds. Likewise, ecoregions tend to be more distinct for smaller‐bodied species and, to a lesser extent, species at lower trophic levels.Main conclusionsWhile ecoregion‐based conservation planning can provide a crucial tool for developing holistic conservation interventions, we show here that the ability to capture and describe communities is not uniform across regions or taxa. In particular, ecoregions tend to best describe communities of small‐bodied species, less vagile and tropical taxa that are typically underrepresented in the scientific literature. While ecoregion classification schemes will continue to provide invaluable conservation guidance, we must think critically about when an ecoregional approach is best suited to informing management.