The effect of environmental heterogeneity on species richness depends on community position along the environmental gradient

Publisher's version/PDFEnvironmental heterogeneity is among the most important factors governing community structure. Besides the widespread evidence supporting positive relationships between richness and environmental heterogeneity, negative and unimodal relationships have also been reported. However, few studies have attempted to test the role of the heterogeneity on species richness after removing the confounding effect of resource availability or environmental severity. Here we constructed an individual-based spatially explicit model incorporating a long-recognized tradeoff between competitive ability and stress-tolerance ability of species. We explored the impact of the level of resource availability (i.e. the position of the community along a gradient of environmental severity) on the heterogeneity-diversity relationship (HDR). The results indicate that the shape of HDR depends on the community position along the environmental gradient: at either end of the gradient of environmental severity, a positive HDR occurred, whereas at the intermediate levels of the gradient, a unimodal HDR emerged. Our exploration demonstrates that resource availability/environmental severity should be considered as a potential factor influencing the shape of the HDR. Our theoretical predictions represent hypotheses in need of further empirical study.The work was financially supported by the National Natural Science Foundation of China (41201050, 31570426 and 31000199) and the Fundamental Research Funds for the Central Universities (lzujbky-2013-k15). CC also benefited from the Program for New Century Excellent Talents in University (NCET-12-0248). JTL was supported by a Discovery Grant from the Natural Sciences and Engineering Research Council of Canada