Relict serpentine populations of Knautia arvensis s. l. (Dipsacaceae) in the Czech Republic and an adjacent area of Germany

Several distinct populations of Knautia arvensis (L.) Coulter s. l. restricted to serpentine outcrops have been found in the Czech Republic and an adjacent area of Germany. They have been determined as diploids or tetraploids despite the fact that only common, non-serpentine tetraploids occur in the area. These plants differ also in their morphology, florogenesis, and in their behaviour within a plant community from all other known taxa within the species. Their origin has been explained by the hypothesis of microevolution of a relict diploid ancestor. The isolated relict populations have not expanded their range, being confined to the place where they originated.