Informed dispersal of the dandelion

Animal migration is highly sensitised to environmental and biological cues, yet plant dispersal is considered largely passive. The common dandelion, Taraxacum officinale, is a classic example of a wind-dispersed plant and has an intricate haired pappus facilitating flight. This pappus facilitates enables the formation of a separated vortex ring (SVR) during flight (1); however, the pappus structure is not static but reversibly changes shape by closing in response to moisture. Here we characterise the biomechanical function of the pappus morphing regarding SVR dynamics and flight capacity. When the pappus closes, the falling velocity is greatly increased and the velocity deficit within the vortex decreased. To understand the implications of this structural-functional change, we used historic meteorological data to simulate dispersal distance. Dispersal distances were reduced with the pappus closed, and so was detachment. We propose that moisture-dependent pappus-morphing serves to retain seeds in favourable moist niches, providing a form of informed dispersal (2) that has not been characterised in plants on such a short-term, responsive time scale (3).

Prospecting and dispersal: their eco-evolutionary dynamics and implications for population patterns

Dispersal is not a blind process, and evidence is accumulating that individual dispersal strategies are informed in most, if not all, organisms. The acquisition and use of information are traits that may evolve across space and time as a function of the balance between costs and benefits of informed dispersal. If information is available, individuals can potentially use it in making better decisions, thereby increasing their fitness. However, prospecting for and using information probably entail costs that may constrain the evolution of informed dispersal, potentially with population-level consequences. By using individual-based, spatially explicit simulations, we detected clear coevolutionary dynamics between prospecting and dispersal movement strategies that differed in sign and magnitude depending on their respective costs. More specifically, we found that informed dispersal strategies evolve when the costs of information acquisition during prospecting are low but only if there are mortality costs associated with dispersal movements. That is, selection favours informed dispersal strategies when the acquisition and use processes themselves were not too expensive. When non-informed dispersal strategies evolve, they do so jointly with the evolution of long dispersal distance because this maximizes the sampling area. In some cases, selection produces dispersal rules different from those that would be ‘optimal’ (i.e. the best possible population performance—in our context quantitatively measured as population density and patch occupancy—among all possible individual movement rules) for the population. That is, on the one hand, informed dispersal strategies led to population performance below its highest possible level. On the other hand, un- and poorly informed individuals nearly optimized population performance, both in terms of density and patch occupancy.