Multispecies resource competition

The main focus of this thesis is the study of competition for resources among many species, from a theoretical position. This is accomplished using the “nutrient storage model” of algal competition. This model is of considerable relevance in plankton ecology and in the field of ecological stoichiometry. Unfortunately, previous research considered just a few species in contrast with the hundreds that are present in real communities. Thanks to analytical and numerical approaches, we can conclude that multispecies competition models with nutrient storage display a rich and complicated dynamics including oscillations, chaos and the coexistence of many species on few resources. To a great extent, the different dynamics are the consequence of specific trade-offs in the species consumption policies, which is also the case for less realistic models of resource competition. In addition, the comparison with other models reveal that there are general rules governing the multispecies dynamics, and such rules are independent of the underlying mechanisms. This robustness is good news for a niche based perspective of community ecology, in which diversity is the consequence of the species properties. However, the addition of more mechanistic detail, like the introduction of nutrient storage, reveals that predictability becomes rather difficult, not to say pointless, because very small variation in biological parameters or initial conditions can lead to equilibrium coexistence, nonequilibrium coexistence, chaotic dynamics, or competitive exclusion. The implication of these contrasting results is that competitive communities may behave in a consistent way from a statistical perspective, but not in a case by case basis.