Structural simplification compromises the potential of common insectivorous bats to provide biocontrol services against the major olive pest Prays oleae

Abstract

Crop production intensification often leads to the structural simplification of production systems. This structural simplification is expected to have strong impacts on biodiversity and the provisioning of ecosystem services, but information about this topic is scarce. For instance, no information exists for Mediterranean olive (Olea europaea) groves, despite olive farming representing a significant share of the agricultural sector in some European countries. We investigated the impact of in-farm and landscape-level structural simplification on the potential of three common insectivorous bats (i.e., Pipistrellus kuhlii, P. pygmaeus and P. pipistrellus) to provide biocontrol services against one of the most harmful olive pests worldwide, the olive fruit moth Prays oleae. Bats and insect surveys were both carried out in olive groves representing increasing levels of structural simplification and during three sampling seasons (spring, summer and autumn). At grove-level, structural simplification was considered as resulting from reduced planting pattern variability (i.e., tree and row spacing) and tree features (diameter at breast height, height of the trunk and canopy area), while at landscape level was considered as resulting from reduced land-cover types. We found that the Kuhl’s pipistrelle was the most frequently recorded species in all types of olive groves and seasons. Moreover, the activity levels of pipistrelle bats as a whole significantly decreased with the structural simplification of olive groves. The abundance of P. oleae was highest at intermediate levels of structural simplification, irrespective of the season. Forest cover in the surrounding landscape had a significant positive influence on the activity levels of P. kuhlii, and a significant and negative influence on the abundance of P. oleae. Our study demonstrates that structural simplification differentially influences the activity patterns of both insectivorous bats and insect pests within olive groves. Moreover, it suggests that structural simplification may strongly compromise biocontrol services provided by bats on the major olive pest P. oleae.