On the polymorphism for cyanogenesis in natural populations of Trifolium repens L. in The Netherlands. I. Distribution of the genes Ac and Li

The cyanogenic phenotypes of 19 populations of adult Trifolium repens plants were determined. Substantial differences were found, both in the frequency of Ac- as in Li-phenotypes. The differences found are not attributable to large climatic differences, but to factors acting on a local scale. Ac and Li are not independently assorted: six out of sixteen populations studied showed a positive linkage disequilibrium. As Ac and Li are not genetically linked, the association must be the result of epistatic selection favouring Ac-Li-phenotypes. The relative importance of deterministic forces, i.e. natural selection, and stochastic ones (founder effects, drift) in determining the phenotypic frequencies found in The Netherlands are discussed.