Post-dispersal predation of Taraxacum officinale (dandelion) seed

1 The importance of predation in determining the fate of post-dispersal dandelion (Taraxacum officinale) seed was investigated. Flowering, seed dispersal, seedling establishment, seed predation and seed predator abundance were recorded in 2002 and 2003, at two sites. Number of flowers were counted in 1-m2 plots, wind-borne seeds were collected in water traps, invertebrate seed predation was estimated from the rate of removal of dandelion seeds exposed on the ground and invertebrate activity density was determined by using pitfall traps. The censuses were made at 2- to 3-day intervals. 2 Seed dispersal occurred 10 days after flowering. Although some seeds were blown away, 3.7-24.2 x 10(3) seeds m(-2) fell to the ground. Four weeks after the peak in seed dispersal 0.7-3.1% of these seeds germinated. Three weeks later only 11-13% of the dispersed seed remained on the ground and most of these were damaged, the remainder presumably having been removed by predators. 3 Predation of exposed seeds was low before seed dispersal but increased after its onset, in parallel with increases in the number of seeds present on the ground and in the activity density of adults of a seed-consuming carabid, Amara montivaga. 4 In cafeteria experiments in which the seeds of 28 perennial and annual herbs were provided A. montivaga consumed the most dandelion seeds, followed by nine other Amara species. In no-choice experiments, under field conditions, A. montivaga consumed six seeds day(-1). 5 Post-dispersal predation, mainly due to aggregation of a single ground beetle species, was more important than that which occurred prior to dispersal. Although predators destroyed c. 97% of the seeds, the effect on dandelion population biology is likely to be small. 6 Post-dispersal seed predation may nevertheless be important in other species, as aggregates of large invertebrate predators can consume large quantities of seed.