Chapter 3.3 - Dispersal Strategies: Are They Responsible for Species Success in Arable Ecosystems?

Abstract

The relation between species success and dispersal can be seen as a feedback process: Efficient dispersal increases the species' success which again increases the species' chance to be dispersed. To be really successful a species first needs specific adaptations to dispersal media to get abundant enough and involved in accidental dispersal processes. A greater knowledge of diaspore dispersal may lead to a better understanding of species' success in agricultural landscapes. The most successful species are those whose dispersal is promoted or at least not disadvantaged by human activity. The existence of a strong selection pressure for high dispersal ability due to disruptive effects of today's farming is suggested. An increasing number of species with efficient dispersal strategies either in space (long distance dispersal) or in time (persistent seed bank) were found. There are two crucial factors which determine dispersal success: the species' dispersal ability and its opportunities to “catch” a dispersal agent. The first depends on the species' morphology and physiology, the second on the individual growing situation of a plant. In agricultural landscapes this growing situation is heavily influenced by human activity. Analyzing the dispersal agents which cause the dispersal processes inevitably leads to the entire spectrum of dispersed species and, therefore, revealing which species benefit from this agent and which do not. Such an analysis results in an estimation of the efficiency of a dispersal agent within a system. An estimation of the dispersal ability of a certain species requires an analysis of all its dispersal strategies and potential dispersal opportunities.