The relationship of environmental (ED) or habitat (HD) diversity of a landscape with its species richness (S) is of much interest. Based on underlying speciesarea (SA) curves, we show that the standard linear relationship lacks theoretical support. The SED relationship is the product of numerous SA curves per habitat and number of distinct habitats in the landscape. We recognize three basic SED patterns: convex, unimodal, concave, based on three fundamental SA curves: power, logarithmic and sigmoid. The preponderance of positive linear or absence of SED/HD relationships reported so far can be attributed to six causes. These include: only testing for linear relationships; limited data sets that exclude small, unique or isolated habitats; regressions are against non-causal variables; and use of biased data that have not been ground-truthed. Hump-backed SED curves should apply widely in regions with species-rich biota and need to resurrected, provided data collected are sufficiently comprehensive and accurate.

This is a preprint of an article published in Nature Communications. The final authenticated version is available online at: https://doi.org/10.1038/s41467-021-27749-9 Large mammal herbivores are important drivers of plant evolution and vegetation patterns, but whether current plant traits and ecosystem geography reflect the historical distribution of extinct megafauna is unknown. We address this question for Southern America (Neotropical biogeographic realm) by relating plant defense trait information at the ecoregion scale to climate, soil, fire, and the historical distribution of megafauna. Here we show that megafauna history explains substantial trait variability and detected three distinct regions (called “Antiherbiomes”) characterized by convergent plant defense strategies, environmental and megafauna patterns. We also identified ecoregions that experienced biome shift, from grassy- to forest- dominated, following the Pleistocene megafauna extinction. These results suggest that extinct megafauna left a significant imprint in the current plant trait and ecosystems biogeography of Southern America.