The realization of early biogeographers that similar environmental conditions would give rise to similar functional groupings of plants is the formative moment of modern biogeography. This simple notion has dramatically altered the trajectory of ecological research, with biomes, biogeographic realms, and ecoregions becoming central concepts of biotic organization. Recent data-intensive analysis has shown that, while ecoregions do delineate distinct biotic communities, their capacity to do so varies across regions or taxa. Given their central importance to global models of the earth system and to the development of conservation plans, it is key to understand when we might expect ecoregion classification schemes to be more useful or less useful, and what abiotic and biotic mechanisms drive this variability. In this paper we integrate ecoregion delineations with data on environmental conditions, biodiversity, and species traits to quantify the descriptive power of ecoregions. We do this by pairing two sources of biodiversity data, GBIF records and global range maps, with environmental layers spanning 4 classes (climate, topography, geochemistry, and human development). We then proceed to use generalized dissimilarity models to describe community dissimilarity across ecoregion borders, and how this varies by abiotic and biotic context.
Results/Conclusions:
From an abiotic standpoint, we report compelling evidence that ecoregion distinctness increases not only with geographic distance, but with greater differences in environmental conditions between ecoregions (p < 0.001). Furthermore, we show that these differences are heightened in warmer (average temperature – 8.2% of model variance explained), less seasonal areas (temperature seasonality – 4.5% of model variance explained). From a biotic perspective, we find that ecoregions are better suited to describe reptiles and amphibians than mammals and birds (p < 0.05). We further find that ecoregions to be more distinctive for smaller bodied organisms and species at lower trophic levels (p ≤ 0.043). Based on these findings we demonstrate how ecoregions can be a crucial tool for developing holistic conservation interventions by safeguarding biodiversity at large, rather than specific species and places. In particular, ecoregions seem well suited to describing changes to communities of small species in regions under-represented in the scientific literature, augmenting their capacity to preserve both biodiversity and the services it provides to humanity into the future.