Résumé
In this chapter, we stress the gaps in our knowledge about dispersal evolution and suggest several promising research directions. (i) Both empirical and theoretical studies illustrate how different causes may result in the evolution of dispersal behaviour. Integrative approaches that study the interactions between these causes are, however, rare. Theoretical expectations must be clarified by a careful comparison with existing models and their specific assumptions. The importance and evolutionary significance of plasticity for dispersal has also been largely neglected. (ii) The evolution of dispersal cannot be understood simply as a change in a single trait. Changes in dispersal rate alter the demographic functioning of populations and their genetic structure, which, in turn, modify the selective pressures on dispersal. Theoretical studies incorporating both types of feed-back are rare, and empirical investigations of such interactions almost absent. Similarly, selective interactions between the evolution of dispersal and life histories are yet largely unexplored. (iii) Knowledge about the determinism and ontogeny of dispersal behaviour is likely to alter predictions concerning its evolution. This includes information ranging from the genetic determinism of dispersal, the effects of hormones on physiology and behaviour, and maternal effects, to the particular environmental cues used by individuals to asses habitat quality. (iv) Experimental evolution should provide information about the relative importance of different causes of the evolution of dispersal, the interaction between demography and the evolution of dispersal, and the joint evolution of other traits. These experiments may also indicate, from comparison of lines before and after selection, which are the genes and/or physiological mechanisms involved in dispersal behaviour.