Article

Current distributions of many European plants are reduced to a mosaic of small isolated populations which have to face the demographic and genetic consequences ofhabitat fragmentation. Apart from environmental and demographic stochasticity, inbreeding depression is considered as an important fa et or determining extinction risks offragmented plant populations. Despite the important theoretical background rega rding the evolutionary dynamics of inbreeding, there is a considerable lack of empirical data to understand how real plant populations respond to inbreeding. In this paper, we suggest that individuai-leve I va riati on in inbreeding depression may play a significant role in decreasing extinction probabi lities of fragmented plant populations, as not ali individuals within a population can be negatively affected by inbreeding depression . We present an overview about conservation genetics, paying special attention to the theoretical significance of family-Ievel variation in inbreeding depression for plant conservation biology. We illustrate theory with preliminary resu lts oftwo ongoing research projects focusing on the conse rvation of plant species in fragmented habitats.