Diversity of aquatic macroinvertebrates, with emphasis on insects, in different rice rotation systems in Uruguay

Rice cultivation is a fundamental agricultural activity in Latin America and occupies a prominent position in the agricultural economy of Uruguay. Rice fields, which are typically flooded for a significant portion of their growth cycle, are considered artificial wetlands with important ecological functions and biodiversity. Associated biodiversity comes mostly from wetlands existing in natural prairies before rice cultivation. Change in land-use for cultivation is the main cause of diversity loss in the world. Uruguayan traditional rice and pasture rotation system favored sustainability and diversity conservation by maintaining vegetation regeneration between crop periods. Recent rice intensification processes, like pasture shortage and crop incorporation in the rotation, threaten diversity conservation. The objective of this study was to identify aquatic macroinvertebrate communities, with an emphasis on insects, as bioindicators associated with different rice crop rotations in Uruguay. This study compared the composition of macroinvertebrate communities in different crop rotations of a long-term experiment and aimed to identify bioindicator groups by delving into their taxonomy. Rotations included: continuous rice, rice with short (1 year) or long (3 years) pasture, and rice-soybean. Found Macroinvertebrate species diversity varied depending on the crop rotation. Rice-pasture rotations exhibited greater diversity compared to continuous rice rotation. The Order Coleoptera (beetles) was the most abundant and diverse group among rotations, a group considered a good indicator of environmental quality. Differences were observed in the composition of insect functional groups among the rotations and sampling dates. Predators and collector-gatherers were the most abundant groups, indicating their probable importance in the biological control of rice pests. The results also revealed differences in the taxonomic richness of insects among the rotations, with greater diversity in rice with pastures. However, the number of collected individuals was low compared to other studies, suggesting the need to combine multiple sampling methods to adequately assess arthropod biodiversity. The study acknowledges certain limitations and suggests the need for more comprehensive and exhaustive sampling to obtain more precise results. In addition, the importance of acquiring a greater understanding of the interactions between aquatic organisms and rice cultivation is emphasized.