Elevational Gradients in Species Richness

The abiotic and biotic gradients on mountains have enor-mous potential to improve our understanding of species distributions, species richness patterns and conservation. Here we describe how abiotic factors change with ele-vation, how flora and fauna respond to these changes and how elevational species richness patterns have been stud-ied to uncover drivers of biodiversity. There are four main trends in elevational species richness: decreasing richness with increasing elevation, plateaus in richness across low elevationsthendecreasingwithorwithoutamid-elevation peak and a unimodal pattern with amid-elevational peak. We discuss the history of elevational richness studies and overview the various hypotheses thought to be important in richness trends, including climatic, spatial, biotic and evolutionary factors