Long-distance dispersal research: Building a network of yellow brick roads

This special issue of Diversity and Distributions presents six papers that contribute to the assembly of a general research agenda for studying long-distance dispersal (LDD) across a variety of taxonomic groups (e.g. birds, fish, aquatic invertebrates and plants), ecosystems (e.g. terrestrial and marine ecosystems, wetlands and grasslands) and thematic fields (e.g. biological transport, marine biology, biogeochemistry and biodiversity conservation). This editorial emphasizes the need to develop a network integrating different research approaches ('yellow brick roads') to address the great challenge ('finding the end of the rainbow') of quantifying, understanding and predicting LDD and its implications. I review the key avenues for future research suggested in the special issue contributions, and stress the critical importance of properly considering the spatial and temporal scales relevant to the process and system of interests. I propose combining absolute and proportional definitions of LDD as a default practice in any investigation of LDD processes. When LDD is defined primarily by an absolute critical distance that characterizes key feature(s) of the system of interest, a quantitative assessment of the proportion of dispersal events expected to move beyond this critical threshold distance should also be provided. When LDD is defined primarily by a certain small fraction of dispersal events that travel longer than all others, an estimate of the absolute distance associated with this high percentile at the tail of the dispersal curve should also be added.