Seasonal and habitat dynamics of parasitoid Hymenoptera in forest fragments and adjacent sugarcane fields

Abstract: Although hymenopteran parasitoids play a key role in biological control, their
responses to seasonal and habitat variation in agricultural landscapes remain poorly understood. Here, we evaluated temporal and spatial patterns in parasitoid abundance, family richness, and community composition in forest fragments and adjacent sugarcane fields in southeastern Brazil. Relationships between forest and sugarcane parasitoid communities were analyzed. Sampling was carried out quarterly using yellow pan traps that were placed four times a year (August, November, February and May) in ten forest fragments and ten adjacent sugarcane fields. Half of the forest fragments were gallery forests, characterized by greater vegetation complexity, and the other half were plateau type forests showing higher disturbance (cutting, wildfires, liana invasion). Generalized linear mixed models revealed that both parasitoid abundance and family richness were higher in forest fragments than in sugarcane fields, and higher in gallery forests compared to plateau fragments. Parasitoid abundance varied seasonally, with significantly lower abundance in November. Parasitoid community composition also showed significant temporal changes, while neither habitat nor fragment type influenced composition. Additionally, parasitoid abundance in forest fragments showed a marginal positive relationship with abundance in adjacent sugarcane fields, but the relationship depended on season and forest type, being stronger in gallery forests. Our results demonstrated that vegetation structure and seasonality are key determinants of parasitoid dynamics in agricultural landscapes of SE Brazil. Forest fragments, particularly structurally complex gallery forests, act as reservoirs for parasitoid communities, emphasizing the role of forest quality in sustaining ecosystem services.