Is declining Campanula glomerata threatened by genetic factors?

Changes in land use lead to increasing destruction and fragmentation of natural habitats. As a consequence, many plant species become rare. Remnant populations are often too small and too isolated to persist over time, and face a high risk of extinction because of genetic, demographic or environmental problems. As the decline of rare species is always a focal point in plant conservation, the aim of this study was to investigate the relative importance of genetics for the probability of survival of Campanula glomerata populations, which are not yet rare but are increasingly on the decline because of land-use changes. We studied 20 populations in three regions in Germany (Saxony-Anhalt, Baden-Wuerttemberg and North-Rhine Westphalia) to assess: (i) whether there is significant genetic differentiation among and between populations; (ii) whether genetic similarity of populations is associated with the geographic distance separating them; and (iii) whether there are relationships between genetic variation and either population size and/or fitness parameters. The results show that the genetic structure of C. glomerata populations is strongly differentiated on a large, but not on a local, scale. As we found neither a correlation between genetic variation and population size parameters, nor between genetic variation and fitness components such as flower number or seed viability/seed germination, we conclude that to date, C. glomerata populations have remained almost unaffected by isolation, inbreeding or genetic drift and are not as yet threatened by genetic factors. We assume that particular life history traits preserve the variability of the populations.