Fluctuating asymmetry in spider‐hunting wasps as a possible indicator of stress in Brazilian Atlantic Forest landscapes

Abstract Habitat loss and land‐use intensification are among the major drivers of biodiversity decline worldwide, leading to measurable effects on organismal morphology, physiology, behaviour and developmental stability that cascade to survival, reproduction and population dynamics. Using fluctuating asymmetry (FA), we analysed whether Trypoxylon ( Trypargilum ) opacum Brèthes, 1914 (Hymenoptera: Crabronidae), one of the species found in the Brazilian Atlantic Forest, reflects the level of stress experienced by certain spider‐hunting wasps. In addition, female wing size was analysed across 18 landscapes with varying characteristics between 2012 and 2024. The landscape metrics used in this analysis included forest, agricultural and pasture cover. FA was estimated using Procrustes scores, while wing size was measured by centroid size (CS). Simple regression analyses revealed a positive relationship between FA and agricultural cover, while CS was positively associated with forest cover and negatively related to agricultural cover ( p < 0.05). These results suggest that populations in more intensively farmed landscapes experience greater developmental instability. Habitat simplification and environmental stressors induced by intensive agricultural management in agricultural landscapes further impair insect developmental homeostasis, increasing the likelihood of reduced developmental stability and increased FA. Although T. opacum is considered a species related to open habitats, our results indicate that forested areas play an important role in promoting larger wing size, likely by providing key prey resources and foraging opportunities.