SEASONAL DIFFERENTIATION - A CONSERVATIVE REPRODUCTIVE BARRIER IN 2 GRASSLAND GENTIANELLA (GENTIANACEAE) SPECIES

18 populations of the grassland biennials Gentianella amarella and G. campestris were cultivated to clarify the genetical vs. environmental components of the flowering phenology, and the reproductive isolation caused by seasonal differentiation. The influence of some environmenta l factors was tested. The seasonal variation persisted in cultivation, and the plants could normally be assigned to distinct aestival or aut umnal groups, with no reproductive contact. Flowering phenology was af fected by environmental factors, but not to such an extent that the re productive isolation was broken. The observed phenological variation w as not reflected by a corresponding variation in present management pr actices. Management history and possible non-anthropogenic factors are discussed as alternative explanations.