Perspectives for Primula fragmented populations in agricultural and urban habitats

Self-incompatible, insect-pollinated plant species are particularly sensitive to habitat fragmentation and pollination disruption because of the need of cross-pollination by pollinators for producing seeds. In Belgium, three Primula species can be found: the rare and endangered Primula vulgaris, the common but locally rare P. veris and the common P. elatior. These distylous, insect-pollinated perennial herbs occur in extremely fragmented habitats, especially in Flanders (small forest fragments or elements of the intensively used agricultural landscape) and Brussels (forest fragments in urban zone). The study of reproductive success, genetic diversity, spatial genetic structure and pollen dispersal patterns revealed genetic erosion, reduced seed production, restricted seed and pollen flow in small and isolated populations of all three species, even to a greater extent for the common ones (P. veris and P. elatior). Being common is thus not a guarantee for long-term survival in fragmented habitats, and conservation efforts should also take common species into account. The local processes (genetic drift, inbreeding) affecting small populations appear to be strengthened when there is recruitment. The distylous breeding system (morph type and ratio, partial self-compatibility) also appear to affect seed set and genetic diversity and structure. Restoration of isolated small populations by increasing population size through regeneration by (inbred) seedling recruitment may lead to negative genetic consequences despite ecological management improving habitats quality. In urban and intensively used agricultural landscapes, restoring large continuous habitat surfaces is unrealistic. So additional management strategies should be considered to compensate the loss of genetic diversity and to reduce inbreeding in these extremely fragmented habitats, such as (1) restoration of gene flow and pollinator movements between isolated populations, by ensuring connectivity through biological corridors, where small populations, especially when they still retain genetic diversity, can act as relay for pollinators; (2) genetic rescue through active population reinforcements

Jaar van publicatie:2008