Biology session

Global biodiversity loss is a growing concern worldwide which threatens ecosystem stability and functioning. With insect decline, processes such as pollination and biological control (reducing pests through natural enemies) are impaired, and the loss of these processes has a substantial effect on agricultural production. At the same time, changes in landscape structure associated with intensive agriculture is one of the main drivers of insect declines, therefore researching and understanding the effects of these factors are of paramount importance.

In this study, we examine the effect of landscape structure on cavity-nesting solitary wasps, bees and their parasitoids in Hungarian villages. We placed trap nests in the centre and the edge of 16 villages surrounded by complex (forested) landscape structure and 16 villages surrounded by simple (agricultural) landscape structure, in order to assess the abundance of solitary wasps, bees and their parasitoids in the area. We also examined the effect of the Normalized Difference Vegetation Index (NDVI) measured in the villages, representing the density and health of the vegetation in a given location.

The number of wasps and parasitoids was significantly higher in villages surrounded by complex landscape structure, while the number of bees remained unaffected. Furthermore, the number of wasps was higher at the edge of the villages in complex landscape structure, while in simple landscape structure the number of individuals was independent of the position of trap-nests within the village. There was a positive relationship between NDVI and the number of bees in both complex and simple landscape structures. In contrast, the number of wasps was mostly unaffected by the vegetation in the villages. Only in villages located in simple landscape structure could we observe a slight increase in the number of wasps with the increase of NDVI. The amount of parasitoids in simple landscape structure increased significantly with the increase of NDVI.

Due to their different lifestyles and environmental needs, landscape structure affects solitary bees and wasps differently. Larger-scale landscape factors were found to be crucial for wasps, whereas local vegetation played a more important role for bees. The parasitoids showed a similar pattern to that of their hosts (bees and wasps), suggesting that the amount of hosts has the most important effect on them. In simple landscapes dominated mainly by agricultural areas, villages with rich vegetation can serve as a potential habitat for wasps, bees, and presumably for other animals as well, thus contributing to the conservation of biodiversity.