Connectivity of cropped vs. semi-natural habitats mediates biodiversity: A case study of carabid beetles communities

Abstract

Green-veining policies aiming at restoring biodiversity in agricultural landscapes mainly focus on the connectivity of semi-natural habitats. However, little is known about the potential role of crop connectivity for the biodiversity using cropped habitats. The goal of the present study was to investigate the effects of habitat connectivity related to annual crops vs. semi-natural habitats (woody elements) on insect biodiversity (carabid beetles) in agricultural landscapes, considering contrasted groups of species in terms of habitat preference and dispersal ability. Results showed that the spatial configuration and connectivity of annual crops in the landscape (here, up to 500 m) can contribute to increased abundance of some groups of carabid species. Spatial continuities between spring and winter crops (in 250 m radius circles) had beneficial effects on farmland species with low mobility (brachypterous) in maize crops, possibly reflecting resource complementation processes. The connectivity of annual crops also had positive effects on abundances of dimorphic farmland species in maize crops and of forest species in woodland, but at contrasted spatial scales (in 250 m vs. 50 m radius circles respectively). The present study also revealed antagonistic effects of landscape patterns related to both crops (edge length between winter and spring crops) and semi-natural habitats (percent cover of woodland) on farmland and forest species, highlighting critical issues regarding the conservation of such contrasted ecological species groups in agricultural landscapes.