Effects of Landscape Structure on Abundance and Family Richness of Hymenopteran Parasitoids in the Olive Agroecosystem

Farming systems maintain ecosystem services related to arthropod biodiversity, which need to be understood for its effective conservation. Some of these arthropods may also be enemies of crop pests. It has been shown that farming systems surrounded by other types of natural or semi-natural land covers/uses are less affected by pests. The abundance and richness of hymenopteran parasitoid (HP) families in olive groves were analysed along a gradient of complexity of the landscape surrounding these agroecosystems. The working hypothesis was that landscape structure is related to the abundance and richness of HP families. Through principal component analysis of samples analysed in 15 olive groves during the springs and autumns of 2015 and 2016, we found that a higher richness of HP families is associated to simple landscapes with olive grove predominance and a lower richness in landscapes with higher diversity of land uses. The most abundant families in olive-dominated landscapes were Pteromalidae, Encyrtidae and Eulophidae , and the least abundant were Elasmidae, Eupelmidae, Chrysididae, Platygastridae and Eurytomidae . In the most diverse olive grove landscapes only three families appeared: Mymaridae , the most abundant, and Diapriidae and Signiphoridae with lower abundance. Scelionidae was the most abundant family in all olive landscapes, both simple and complex, suggesting that their presence is more related to geographical components of latitude and longitude, which were also analysed. The greater richness and abundance of HP in olive-dominated landscapes does not guarantee biological control, but it does provide conservation of arthropod biodiversity as a cross-cutting ecosystem service.