The influence of geographical distance on the decay of beetle community similarity: Native habitat and agricultural monocultures

Abstract 1. The replacement of native habitats by monocultures has led to the loss of insect biodiversity, including beetles. 2. In an attempt to minimize this loss, Brazilian legislation requires farmers to conserve a proportion of farmland as a Legal Reserve. 3. In this study, we investigated the decay of similarity in beetle communities of soybean monocultures compared to Legal Reserves. 4. To do this, we studied 77 sample points distributed across the transition zone between the Amazon and Cerrado biomes, with a maximum distance of 625 km between the farthest points. 5. Our results show that the transformation of forest areas into monocultures causes a drastic decrease in beta diversity for both herbivores and predators. 6. This pattern is not observed in Legal Reserves, where the communities are, for the most part, different in a short geographic space. 7. We noted an increase in beta diversity between sites at a shorter distance (200 km) compared with soybean monoculture areas (350 km). 8. In these environments, many species are generalist pests that benefit from the simplified landscape. 9. To verify the relationship between species dissimilarity and geographic distances, we used the Chord‐Normalized Expected Species Shared dissimilarity index, replacing Bray–Curtis due to its robustness in dealing with small samples or subsampling. 10. We reinforce the importance of Legal Reserves in conserving beetle biodiversity, emphasizing the need for preserved areas distributed throughout the landscape as they play a crucial role in maintaining beta diversity and preserving ecosystem services in anthropized landscapes.