A unifying evolutionary theory for the biomass-diversity-fertility relationship

Although a widely accepted ecological theory predicts that more diverse plant communities should be better able to capture resources and turn carbon dioxide into biomass, the most productive communities known are low diversity agricultural ones. This paradox has fuelled a long running controversy in ecology surrounding the nature of the relationship between diversity, productivity and fertility. Here, an evolutionary computer model is used which demonstrates that given the opportunity, species-rich communities may evolve under high fertility conditions. In contrast to low diversity, highly productive agricultural communities are shown to probably be a recent phenomenon. In simulations where fertility was applied to communities that had evolved under lower nutrient conditions, a few species had the ability to become 'dominant'. These species were responsible for the loss of diversity and for the majority of biomass production. These results are consistent with complementarity theory applying in nature in old co-evolved low nutrient communities, whereas in recently established fertile agricultural communities, dominant species appear to regulate biomass production. Understanding the nature of these 'dominant' species throws light on our understanding of phenotypic plasticity and the ecology of invasive species.