Diversity by temporal oscillations in plant communities with a differential timing of reproduction

Abstract

Background and Aims: Species can coexist at non-equilibrium circumstances, for instance by oscillations in population densities or chaos, caused by non-linear responses of species to their environment. We analyzed whether plant genotypes that vary in their timing of reproduction can coexist under equilibrium or non-equilibrium circumstances when competing for light. Methods: We used a game theoretical approach, based on a biologically mechanistic model of plant growth. Key Results: In our model, the genotype switching to reproduction slightly later than its competitor attained a higher fitness. This caused a succession from early switching genotypes to those switching later to reproductive investment. However, there were cyclic opportunities for extinct genotypes that switch early to reproduction to re-establish and grow into the community. The cause was that genotypes that switched very late produced relatively very little seed because of an overinvestment in vegetative growth; especially when competing against individuals of the same genotype. Because the very early switch genotypes could establish, circumstances were such that other extinct switch genotypes could re-enter the vegetation as well. In this way the diversity of genotypes was maintained over time by temporal oscillations of genotype abundances. Conclusions: We show that within a model, an externally undisturbed plant community can produce its own temporal cyclic or chaotic disturbances to promote diversity, rather than converge to a stable equilibrium when competing for light. Cyclic fluctuations in species composition can occur in a model community of plants sharing the same growing season and that are limited just by light as a single resource.