Habitat fragmentation, caused by human activity such as land conversion, is affecting many plant species by increasing the spatial isolation between the remaining populations and by decreasing population sizes. Fragmentation is believed to affect the fitness of plant species through decreased genetic diversity, decreased reproductive output and disturbed plant-pollinator interactions. Yet, strong empirical evidence on the negative impact of habitat fragmentation on the viability of the remaining forest plant populations is scarce. This might be explained by the relatively slow responses of forest plants due to their clonal character and long generation times. Recent limited empirical and theoretical suggests that it may take 50 up to 100 years or even more after the initial fragmentation of a landscape before populations in small and isolated patches decline to the level of extinction. Therefore, it is likely that an extinction debt, defined as incongruence between the patch occupancy of a species and the present landscape structure, exists for plant populations in the fragmented forests of Western Europe. Thus, in the relatively short term substantial extinction of forest plants due to historical fragmentation can be expected. The general objective of this research project is to examine the effects of forest fragmentation on forest plant species and to identify a possible extinction debt. We will use an integrated ecological and population genetic approach on three model species with different life history traits (Geum urbanum, Mercurialis perennis and Circaea lutetiana). The following points will be realised.Relating fragment sizes, population sizes and isolation of the fragmented populations at the landscape scale with their genetic structure, reproductive success and plant-pollinator interactions. Close integration of the ecological and genetic data. At present, this integration is usually lacking in many studies. All variables regarding genetics, reproduction and fruiting success will be measured in the same populations and of possible on the same individuals This allows an estimation of the relative importance and the interaction between several fragmentation-related processes Determine minimal area and maximal isolation parameters to guarantee population persistence in the fragmented landscape. Propose guidelines for conservation.