The Evolutionary Ecology of Dispersal

Dispersal is a life-history trait that has profound consequences for populations. Viewed from an ecological perspective, dispersal influences the dynamics and persistence of populations, the distribution and abundance of species, and community structure. From an evolutionary perspective, dispersal determines the level of gene flow between populations and affects processes such as local adaptation, speciation, and the evolution of life-history traits. In fact, it is difficult to imagine any ecological or evolutionary problem that would not be affected by dispersal. The various consequences of dispersal are extensively discussed in the ecological and evolutionary literature (a search in the Science Citation Index gave more than 1000 occurrences of 'dispersal' in the abstract or title of papers for the year 1997 alone). Surprisingly, however, the question of why particular dispersal strategies evolved has received much less attention. Part of the problem is that many of the mechanisms proposed to affect the evolution of dispersal (Box 1) are notoriously difficult to test in the field. Consequently, there exists a serious gap between theory and data, and our understanding why particular organisms disperse in specific ways is still limited. A recent workshop in Finland provided an opportunity to survey the state of the field.