Demography, reproductive biology and adaptive traits in Gentianella campestris and G. amarella: evaluating grassland management for conservation by using indicator plant species

The status of Gentianella campestris and G. amarella (sensu latu) in the central and southern parts of Sweden is evaluated by studying changes in their distribution and abundance over the last 50 years, the reproductive system, and the effects of various types of grassland management on seed production and demography. Both species are highly specific to grassland habitats and the results obtained for the genitians can be useful for evaluating grassland status and grassland management in general. G. campestris and G. amarella have disappeared from 88-98% of the localities from which they have been recorded 50 years ago. This decline is mainly due to ceased grassland management, but the extinction rate is considerable also in habitats with continued management. Both species are phenologically variable and cultivation experiments revealed that the phenology had genetic components and was little affected by environmental conditions. In addition, seasonal differentiation provided a conservative reproductive barrier between early flowering and late flowering ecotypes. G. campestris and G. amarella are hapaxanths and thus dependent on regular recruitment. Pollination experiments showed that most populations were autofertile and obtained full seed set without external pollination. The rosettes and adult plants appeared to be negatively affected by high turf and the seedlings by thick litter layer. Consequently, the genitans are exceedingly depending on management that keep the vegetation low and counteract litter accumulation. However, different management methods yielded large differences in seed production, demography and population viability. These parameters were affected by type of management (grazing, mowing and mowing with subsequent grazing) as well as by the timing of mowing or grazing. Seed production was determined by the plant's ability to deal with damage caused by grazing or mowing. Two alternative strategies were found in G. campestris: the plants either avoided damage by flowering early, or tolerated damage by high capacity for compensatory regrowth in combination with late flowering time.