Effects of population size and genetic variation on the response of Succisa pratensis to eutrophication and acidification

1 Succisa pratensis , a characteristic plant species of biodiverse, slightly acidic grasslands (NARDETEA), has declined in the Netherlands over recent decades. This process has mainly been attributed to environmental stress caused by anthropogenic acidification and eutrophication, although genetic deterioration and decreasing population size may also be involved. 2 We analysed the combined effects of environmental stress, genetic variation and population size on the performance of Succisa pratensis . 3 Individual plant performance was negatively affected by eutrophication and, to a smaller extent, by acidification. Plants originating from smaller populations performed less well and showed less genetic variation and higher inbreeding coefficients than plants from large populations. Strong interactions between population size and stress treatments reflected the fact that plants from small populations suffered more from deteriorating soil conditions than those from large populations. 4 abitat fragmentation may reinforce the negative effects of environmental stress, leading to even the less effective treatment (acidification) having serious consequences.