Abstract
The intensification of agricultural practices has induced the local, national and regional extinction of many species and also affected ecosystem services provided by biodiversity such as biological control of agricultural pests. We model the population dynamics of Pterostichus melanarius (Coleoptera: Carabidae), a carabid beetle often used as indicator species of habitat changes, by a joint model that combined a matrix model of population dynamics including local dispersal with an explicit model of the patchy landscape of the polders of the Bay of Mont St. Michel (Brittany, France). We used this model to evaluate the effects of landscape composition and configuration on the spatial population dynamics of this carabid beetle, and also investigated the consequences that different management strategies of the structure and composition of an agricultural landscape can have on its abundance and spatial distribution. The results of this study highlight that semi-habitats (field edges, dykes, hedgerows) usually considered as shelters for wintering play a key role as well for summer recruitment. We find that there is an optimal cluster size of patches for population viability that is induced by the seasonal movement of P. melanarius. However, the effect of increasing the amount of semi-natural habitats patches on the viability of this population critically depend on the spatial arrangement, connectivity and spatial alternation of the network of semi-natural habitats, a feature that should be considered in the conservation and management actions in the landscape context.