LOCAL PLANT DIVERSITY PATTERNS AND EVOLUTIONARY HISTORY AT THE REGIONAL SCALE

Abstract

The effect of evolutionary history on local-scale diversity patterns has often been suggested, but not shown. I explored whether widely described local-scale relationships between plant species richness and soil pH are related to evolutionary history. I expected positive relationships to occur between richness and pH if the pool of species that is suited for high pH soil is larger than the pool of species that is suited for low pH soil. In contrast, I expected negative relationships to occur between richness and pH if the pool of species that is suited for low pH soil is larger than the pool of species that is suited for high pH soil. I call this the species pool concept, because the direction of the relationship between richness and pH depends on whether the species pool has evolutionary origin on soils of high or low pH. I used 85 published studies from all over the world and found that positive relationships between richness and pH were significantly more probable in floristic regions where evolutionary centers were on high pH soils, and negative relationships between richness and pH were more probable in regions where evolutionary centers were on low pH soils. Because soil pH increases with latitude, I also found that the relationship between richness and pH was positive at high latitudes and negative at low latitudes. Consequently, local relationships between plant diversity and soil pH are clearly related to evolutionary history.