Evolution of dispersal in asexual populations: to be independent, clumped or grouped?

The question Why to disperse? has been extensively investigated from an evolutionary perspective, and the strategy to disperse can be explained by several proximate and ultimate factors. The amazing diversity of dispersal mechanisms that animals, plants, fungi, peat mosses and other organisms have developed leads to the following question: How to disperse? In this article, we introduce an original modeling framework to study the evolution of dispersal in asexual populations where reproducing individuals release propagules and can adopt (by mutation) three strategies: independent movements of all propagules, clump dispersal (i.e. clumps of propagules attached together and settling at the same location), or group dispersal (i.e. groups of propagules simultaneously released and settling at different but positively correlated locations). We show how the spatial limits and fragmentation of the species’ habitat shape the frequencies of the three strategies in the population and the sizes of groups and clumps. The co-existence of the independent, clump and group dispersal strategies at the stationary state of the population dynamics is of particular note. However, group dispersal never appeared as a dominant strategy, whereas independent and clump dispersal were both dominant for different parameter ranges (essentially because dispersal is either adaptive or maladaptive) .