Non-crop habitats modulate alpha and beta diversity of flower flies (Diptera, Syrphidae) in Brazilian agricultural landscapes

Non-crop habitats play a key role in maintaining functional diversity and ecosystem services in farmland. However, the interplay between beneficial insects and landscape variables has rarely been investigated in Neotropical agroecosystems. We used flower flies as a model group to investigate the effects of landscape attributes on beneficial insects in agroecosystems across a gradient of landscape complexity. We specifically ask: (i) Do the abundance and species richness of flower flies in cereal crops increase with increasing landscape complexity? (ii) Do the effects of landscape variables on local flower fly communities differ between spatial scales? (iii) How do landscape complexity and local factors (crop size, altitude and insecticide applications) affect beta diversity? We sampled flower flies in 54 edges within 18 wheat crops in Parana State, southern Brazil. The percentage of non-crop habitats, landscape diversity and edge density were the explanatory variables, which were calculated at multiple spatial scales for each landscape. We collected 8340 flower flies, distributed in 12 genera and 52 species. Species richness was positively associated with the percentage of non-crop habitats, but total abundance presented non-clear pattern. However, abundance without the dominant species was also positively associated with the percentage non-crop habitats. Similarly, beta diversity was related to non-crop habitats, suggesting that the reduction in non-crop habitats implies in species loss. We have provided the first insights into the importance of non-crop habitats on the conservation of beneficial insects within Neotropical farmlands. To guarantee high levels of biodiversity within agroecosystems we need to promote the conservation and restoration of non-crop habitats in the surrounding landscapes.