| Summary: | Explaining spatial variation of species richness is a central goal of ecology. Recently it has been shown that the number of species is related to energy availability. There are two major categories of hypotheses concerning possible processes behind this relationship: i) hypotheses based on an assumption that the total number of species at given site is limited by the total amount of resources, and ii) hypotheses assuming that evolutionary and historical processes are mainly responsible for the current species richness patterns. We tested possible explanations concerning both resource limitation and evolutionary history using datasets of herbaceous plants, trees and dragonflies, varying in their scale and extent. Within local communities of herbaceous plants, the number of species was influenced by the total amount of available resources (productivity), through its effect on the total number of individuals and the intensity of interspecific competition. However, the role of resource limitation was not strong, and the form of the resulting species-productivity relationship was affected by habitat heterogeneity acting independently of productivity. Historical processes affecting the size of species pool appeared also as important at this scale (Chapter 1). Within local communities of trees...
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