Traditional almond orchards in contrasting landscapes maintain extremely diverse parasitoid communities threatened by abandonment

Abstract Hymenopteran parasitoids are an extremely diverse insect group, crucial for ecosystem functioning and pest control. Due to their high trophic level and high degree of specialization, parasitoids are particularly sensitive to disturbance and extinction events, which makes them good indicators of arthropod diversity. Different studies have shown that parasitoids can be affected by management practices and landscape composition and configuration but few have evaluated the consequences of agricultural abandonment, a process that threatens the high biodiversity associated with European High Nature Value Farmland. In this context, we aimed to determine the effects of traditional almond orchard abandonment on the hymenopteran parasitoid community (at genus level), the role of landscape complexity in mediating these effects, and the impact of several land-use variables at different scales, in Spain. Traditional almond orchards supported a highly diverse parasitoid community, more abundant and richer than that of abandoned orchards in certain months, particularly when surrounded by a high cover of semi-natural habitats. The landscape context influenced the effects of agricultural abandonment: abandoned orchards served as refuges in late summer only in simple landscapes, whereas complex landscapes generally favored parasitoid abundance, especially in traditional orchards. The strong seasonality drove a high turnover rate and shaped community responses to land-use variables at both 150 m and 500 m scales.