Biodiversity and Ecological Theories

Abstract

Recent publications have pitted, on the one hand, the neutral theory of biodiversity – that leaves ample room for demographic processes such as reproduction, mortality, migrations, extinctions and speciation that have major random components – and, on the other hand, the ecological niche theory, more deterministic, that favours relationships with the environment and mechanisms between populations, especially competition. These two ecological theories, the foundations of which we review in Sections 5.1 and 5.2 of this chapter, do not truly include the other levels of biological organisation where, as we have seen, processes of diversification play a role. They are, in fact, complementary if we assume that the same niche can be shared by different species, phylogenetically close or not, and that, simultaneously, demographic processes – the keys to the neutral theory – play a major role. In fact and as is customary in demographic approaches, we introduce environmental constraints by varying the demographic parameters or by observing variations that we can attribute to environmental factors. First, here are some obvious facts.