Speirochore Ackerwildkräuter: von ökologischer Spezialisierung zum Aussterben )

Abstract

Until recently the most important weeds of cereal and flax cultures in Central Europe were those with diaspores adapted to dispersal with crop seeds (speirochores). Such weeds obviously originated through the selection pressure in arable fields and persisted there thanks to the traditional methods of cultivation. Studies of the segetal vegetation in the Gorce Mts. (Polish Western Carpathians) in the 1950-ties demonstrated that at that time the speirochores formed the major part of weeds strictly associated with cereal and flax fields, and that their diaspores dominated in the seed of local origin which was used by the farmers for sowing their crops. Lateron qualified sowing material was generally introduced, and very soon a sharp decline of speirochoric weeds was noticed. Specialized linicolous weeds became extinct as early as in 1960-ties. According to the phytosociological survey of cereal fields in 1985 several speirochoric weeds formerly occurring in this type of habitats also disappeared, and many others became much less common than 30 years ago. Thus a narrow ecological specialization of these species turned out to be the ultimate cause of their extinction.