The structure of a local community is determined by two main components: (1) the pool of species present, i.e. a subset of the regional fauna; (2) the environmental structure as it is perceived by the species. The composition of each regional fauna is determined by the history of its formation. This includes the biogeographic history of a region (invasions and/or extinctions of some taxa) as well as the processes of adaptive evolution of its constituent taxonomic elements. The environmental component of community structure is determined both by historical and current processes. Historical processes include the history of landscape evolution and the evolution of specific responses to this landscape. Current processes include relationships between landscape diversity and species distribution. In other words, community structure is determined by the occurrence of specific environmental diversity on one hand, and by the manner in which the local species perceive this diversity on the other. As a result, the structure of each local community is ecologically specific (the ratio between specialist and generalist species, types of ecological specialization, etc.). Historical processes play an important role in community structure and lead to the diversification of community structure. In contrast, there are common ecological rules governing desert rodent communities that lead to the convergence of community structure. Thus far we do not know the relative importance of these two processes either generally or in each particular case.
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