Martínez Núñez, Carlos; Rey, Pedro
Understanding how agricultural intensification affects different groups of species and different types of interactions (e.g., pollination and predation) is an interesting challenge, which can also help us to improve management in agricultural landscapes.
In this study, we use bee hotels (artificially provided cavities such as reed stems where some bees and wasps nest) to study how pollination and predation vary across olive groves under conventional and organic management. To do this, we build interaction networks that include all the studied groups and types of interactions (called hybrid networks) that occur in these bee hotels. Then, we dissect these hybrid networks to see how many different interactions of each type we find. For instance, how many different mutualistic interactions, or intraguild predation (predators eating other predators), or competition for prey, are there in each network?
We analyse how the frequency of each type of interaction varies on farms under different management regimes. Last, we also calculate functional spaces of networks defined by the frequency of different types of interactions, to see how these functional spaces vary and overlap between sites and conditions.
Results showed that mutualistic pollination interactions were more frequent in organic olive groves, and that these types of interactions were relatively stable across sites compared to predation interactions. In contrast, although direct predation interactions were more frequent on organic farms, intraguild predation was more frequent in conventional groves.
This study shows how agricultural intensification can jeopardize both mutualistic interactions and direct predation interactions but, at the same time, can benefit predators that can feed on many different species in these bee hotel systems.