Natural triploidy in Centaurea and Cheirolophus (Asteraceae).

Abstract

Sporadic triploid counts have been an intriguing constant in our researcb on karyology of the subtribe Centaureinae. We present in this paper some uew triploid records anda survey of the documented triploidy in the group. On the basis of these and other examples in the subtribe, a tentative hypothesis on the origin of triploidy in Centaurea s. 1. is elaborated. Our hypothesis is that triploidy in the group is closely related to the pattern of growth in some sections of Centaurea. These sections, especially Acrocentron, grow in scattered small populations in which genetic drift may lead to incompatibility.