Landscape and agri-environmental scheme effects on ant communities in cereal croplands of central Spain

Abstract

Agri-environmental schemes (AES) of the Common Agricultural Policy (CAP) aims at reversing the negative effects of agricultural intensification on biodiversity and ecosystem services. Landscape context may modulate, and even constraint, AES effectiveness. We evaluate AES effectiveness on ant abundance, diversity and community composition. Ants are an ecologically dominant group whose response to conservation efforts in farmland has been rarely evaluated, despite its role in weed control, particularly in Mediterranean farmland. Ants were sampled in the edge and in the centre of paired cereal fields, managed with and without AES in three study areas along a landscape complexity gradient. AES application had no significant effects on ant species richness or ant community composition. Richness increased in fields and landscapes with higher amounts of complex edges and decreased towards the centre of the fields. Specialist granivorous ants (harvester ants, Messor spp.) were the most abundant. Abundance of foraging ants increased with the amount of complex edges around fields and in the landscape. AES application increased ant abundance close to field edges but not in field centers. AES fields had less specialist granivorous foraging in their centers than in control field centers. Ant communities in Mediterranean cereal cropland were mostly constrained by the availability of complex edges, needed for nest building. AES increased the abundance of foraging ants, mostly specialist harvester ants, and its potential service of weed control, but close to field edges mainly. Measures promoting the abundance of stable edges rather than of ephemeral headlands in the landscape are essential to enhance the potential of AES for increasing ant-mediated ecosystem services of weed control