Stable coexistence of equivalent nutrient competitors through niche differentiation in the light spectrum

What explains the coexistence of species? Answering this question may help ecologists to predict how natural communities will respond to environmental change. We transferred phytoplankton communities from the North Sea to laboratory competition experiments. The experiments resulted in coexistence of two species. Monocultures revealed that these two species were equivalent competitors for phosphorus. Yet, in competition, the species displayed stable coexistence rather than the random ecological drift predicted by neutral theory. Interestingly, the two species used different pigments absorbing different colors of light. Hence, coexistence of these equivalent nutrient competitors was stabilized by niche differentiation in the light spectrum.