Effects of Atlantic Forest conversion to introduced pastures on abundance and body size of two Neotropical flower chafer beetle species

Abstract Land-use change is a major driver of biodiversity loss, yet its effects on intraspecific morphological and population responses in many insect groups remain poorly understood. In the Brazilian Atlantic Forest hotspot, native habitats continue to be rapidly converted into introduced pasturelands, potentially altering not only species abundances but also functional trait expression. Here, we evaluated how land-use change influences abundance and body size of two Neotropical flower chafer beetles, Gymnetis chalcipes Gory & Percheron, 1833 and G . pantherina Blanchard, 1837 (Coleoptera: Cetoniinae: Gymnetini). Beetles were sampled in native forests and introduced pastures (African grasses – Urochloa spp.), and abundance and body size were measured to assess demographic and morphological responses to habitat modification. Both species showed significantly higher abundances in native forests, indicating that pasture establishment negatively affects population size. However, morphological responses were species-specific: G . pantherina exhibited reduced body size in pastures, whereas G . chalcipes showed no significant difference between land-use types. These contrasting patterns reveal that abundance and body size do not respond uniformly to environmental change, suggesting differences in ecological strategies and sensitivity to environmental filtering. Our results provide evidence that incorporating trait-based metrics can uncover subtle effects of land-use change that may be overlooked when relying solely on abundance patterns. These findings highlight that native forests act as environmental filters that preserve morphological structure and enhance population resilience of flower chafer beetles in tropical landscapes affected by human activities.