Comparative assessment of aquatic macroinvertebrate diversity in irrigated rice fields and wetlands through different spatial scales: an additive partitioning approach

Abstract

The role of rice fields as refuges for wetland macroinvertebrates was assessed at multiple spatial scales, and macroinvertebrate diversity was compared between fields and natural wetlands. Because irrigated rice fields are highly disturbed environments, and have lower environmental complexity and heterogeneity in the irrigated phase than do wetlands, we hypothesised that the fields would sustain lower diversity than do wetlands, especially at broader spatial scales. Wetlands and rice fields from three regions in southern Brazil were simultaneously sampled. In wetlands, the broadest scale (hydrographic basin) contributed the most to macroinvertebrate diversity. In rice fields, besides hydrographic basin level, narrower scales (site level) also contributed to macroinvertebrate g diversity. Different cultivation and management systems may be responsible for the contribution of narrower scales to g diversity in rice fields. Differences in community structure in both environments were determined by wetland drainage practices, and they were affected by the ENSO climatic phenomenon, which influenced macrophyte diversity in wetlands. Wetland communities were characterised by macrophyte-associated, passive-dispersing taxa, whereas rice fields contained short-lived, active-dispersing macroinvertebrates. The present study demonstrated that rice fields do not represent suitable refugia for wetland-expelled macroinvertebrates because they do not support similar community structure, at least under some management practices and climatic conditions influenced by ENSO.

Benthic macroinvertebrates and degradation of phytomass as indicators of ecosystem functions in flooded rice cropping

“…During the sampling period, sensitive organisms to environmental changes, such as Ephemeroptera (Kerans & Karr, 1994) were not found in the conventional systems, which corroborates data of Pires et al (2015).…”

“…The abundance of benthic macroinvertebrates was higher (p<0.05) in the natural wetland than in the cultivated fields, which is opposite to what was reported by Pires et al (2015), who evaluated irrigated rice farmings during the crop season, and reported drought problems at the time of the study. In the present work, abundancy in the site of the organic farming was higher (p<0.05) than in the conventional one, in accordance with the results obtained by Wilson et al (2008) during the crop season.…”

“…From these predators, Acari were the major representatives in the natural wetland, while Nematoda were predominant in the cultivated fields. Probably, this distribution is due to Acari sensitivity to physical disorders (Di Sabatino et al, 2000), according to the sensitivity range of macroinvertebrate families of Costa Rica (Rizo-Patrón V. et al, 2013). The comparison of the occurrence frequency (Table 4) with this scale showed that in the conventional rice cultivation, accessory and constant families are the only ones classified as sensitivity 3.…”

“…According to Pires et al (2015), the fauna recorded in the conventional system is usually rich and diversified; however, it is characterized by a high ecological dynamism, and by its composition of environmental disturbance-tolerant groups, with a high capacity for colonization. During the sampling period, sensitive organisms to environmental changes, such as Ephemeroptera (Kerans & Karr, 1994) were not found in the conventional systems, which corroborates data of Pires et al (2015).…”

Effects of wetland hydroperiod length on the functional structure of assemblages of Odonata

“…; Pires et al . ). Different life‐history strategies occur in freshwater insects in relation to habitat drying, and these include presence of diapause and changes in the life cycle (Batzer & Wissinger ; Verberk et al .…”