Article

After a presentation of recent studies on gene tlow and on pattems of genetie variation in pl ants, a brief evaluation is given of the effects of fragmentation of the landseape on the genetic variation in pianI species and the consequential effects or in breeding depression. Data show that reduced fitness in small and isolated populations oceurs, owing to reduced reproduetive success (Iower fruiI or seed set) and beeause of inbreeding. It is also suggested that the stili poorly studied mechanism of outbreedi ng depression may also have negati ve effects. In partieular, outbreeding speeies that used to be widespread and common, suffer more from fragmentation and isolation than endemie and naturally rare species or predominant selfers. More emphasis should be plaeed on the eonservation of new rare species, beeause their ecotypic variation and manifold , but often undiscovered local adaptations may get lost, and eonsequently also their long-term evolutionary perspectives.