Centres of dispersal and evolution in the neotropical region

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Abstract
For the first time, centres of dispersal in the sense of De Lattin (1957) have been analysed for South and Central America. According to the results of this analysis, at least 40 centres have to be considered, the situation of which has been influenced by quaternary climatic fluctuations and vegetation fluctuations. The latest rate of differentiation of the faunal elements, which have to be associated with the centres (subspecific level) can be understood for a temporary indicator of the last function of the centres in the sense of centres of preservation of faunas and floras during regressive phases. The isolation of the montane forest centres occured before that of most of the lowland forest centres of the central and northern part of South America. During a postglacial arid phase, there has been a gene flow, via open migration roads, between numerous Amazonian Hylea‐Campo populations and populations of the costal savanna of Guiana, Venezuela and the Campo Cerrados. At the same time, these migration roads played the role of barriers of dispersal to the forest fauna and were reconquered by the forest at the end of the aridity phase. At the present time, transition zones of subspecificly differentiated forest populations can be found within the range of these old migration roads. Although the Campo Cerrado has been acting as a barrier of dispersal to forest species since the beginning of the postglacial arid phase, it had obviously been passed through by Amazonian and Serra‐do‐Mar faunal elements prior to that time. The location of the centres of dispersal and the differentiation of their faunal elements support the assumption that the great richness in species of neotropic biomes may be attributed to a large extent to quaternary biochore shifts and the resulting constant isolation of populations. Independent of this, however, numerous faunal elements indicate that this latest phase of differentiation is, in many cases, based on much older ones.