Drivers of Elevational Richness Peaks, Evaluated for Trees in the East Himalaya

A mid‐elevation peak in species richness is common in many clades. Here, we studied trees of the east Himalaya and found a richness peak at 500–1,000 m. We argue that this results from a correlation of climate with both the numbers and kinds of species, coupled with a geometric constraint in which range expansions from the plains introduce few new species at the base, whereas just above the base, novel species have ranges extending from both above and below. We develop a mathematical model to derive conditions for this to happen. A prediction is that species’ elevational ranges should be smaller at lower elevations, as we find. These photographs illustrate the article “Drivers of elevational richness peaks, evaluated for trees in the east Himalaya” by Suresh K. Rana, Kevin Gross, and Trevor D. Price published in Ecology. https://doi.org/10.1002/ecy.254