Relationship between landscape structure and abundance of airborne beneficial arthropods in an olive agro-ecosystem

Abstract

Some of the groups of beneficial arthropods present in the olive grove canopy are hoverflies, hymenopteran parasitoids and bees. In this research we test the hypothesis that the abundance of these groups in olive groves increases with increasing landscape complexity. In spring 2015 and 2016 we determined the abundance of the beneficial insect groups in 15 olive groves by identification of insects captured on 4 yellow sticky traps in each olive grove. Indices of landscape structure were calculated in circular areas with radii ranging from 250 to 1500 m around the 15 olive groves selected. Preliminary results indicate that in both sampling dates, the abundance of hoverflies was negatively correlated with the patch size of the olive grove, but positively correlated with the total area of scrublands and oak forests and with the diversity index of land uses. The abundance of hymenopteran parasitoids and bees was also positively correlated with the total area of scrublands with oak, in both years, but negatively correlated with the patch size of olive groves in the case of bees. Not all these relationships were significant at all radii and years analysed. These results indicate that intermingling of spontaneous vegetation with olive groves favours the presence of beneficial arthropods.