Gisele Daiane Pinha

Temporal nestedness in Chironomidae and the importance of environmental and spatial factors in species rarity

Biological communities are composed of a few common and many rare species. An understanding of the mechanisms that govern the distribution of these species is fundamental to knowledge regarding community ecology. Our hypothesis is that chironomid larvae follow a nested distribution in relation to hydrological periods in Neotropical floodplain lakes, whereby the flood period composition is a subset of the drought periods with a predominance of common species. We collected samples from 18 lakes in 2011 in a flood month and three drought months. The community followed a nested distribution where the spatial factors were more important for rare and common species during the flood and for the common species during all months. Thus, with the increasing connectivity and similarity of environments during the flood, neutral processes, as the dispersal, would govern the community. Conversely, environmental factors were more important for rare species in the drought, which suggest that these species are more specialists, largely influenced by niche-related processes. Thus, our study emphasizes the complexity of biological communities specifically concerning how environmental, spatial, and temporal factors influence community dynamics among species groups.

Habitats and trophic relationships of Chironomidae insect larvae from the Sepotuba River basin, Pantanal of Mato Grosso, Brazil

Benthic habitats are linked by physical processes and are essential elements in assessing of the distribution dynamics of Chironomidae dipteran insects and their role in aquatic ecosystems. This work presents results of distribution patterns of chironomids larvae in 38 sites that are abundant in the study site, inhabiting the substrate of the main river channel, rapids, tributary brook, floodplain lakes and reservoir along the Sepotuba River from its mouth at the Paraguay River to the headwater region. A total of 1,247 larvae was registered. The most abundant taxa were Polypedilum (Tripodura) sp. (25.2%), Cricotopus sp.3 (23.0%) and Tanytarsus sp. (15.0%). Fissimentum desiccatum were found only in the reservoir; Fissimentum sp.2 and Tanytarsus cf. T. obiriciae sp.2 in floodplain lakes, and Goeldichironomus sp. in the main channel. The low diversity of the sites S06 and S35 is caused by the near-exclusive presence of the species Cricotopus sp.3, alone or together with one or another taxon (Tanytarsus sp., Djalmabatista sp.3). Collectors-filterers represent 16%, collectors-gatherers 15%, predators 11% and scrapers only 1%. The predators dominated in the secondary channel (±88 ind/m2), corresponding to 40% of the total of this group. Cryptochironomus sp.2 (34%) and Ablasbemyia gr. annulata (26%) were the most abundant among the predators. The differences along the river course are decisive for the formation of distinct or discontinuous communities and the limits become obvious though the interrelations between the populations in the community, as for instance, competition for food and habitats.

Dispersal mode and flooding regime as drivers of benthic metacommunity structure in a Neotropical floodplain

The metacommunity approach emerged with the interest in investigating how local and regional processes interact to determine community structure. However, species distribution may differ according to biological features (e.g., dispersal mode) or system connectivity. We investigated the distribution patterns and the importance of environmental and spatial variables for benthic invertebrate metacommunity structures in a Neotropical floodplain according to hydrological periods (flood and drought) and dispersal modes (active or passive). We sampled 18 lakes during flood and drought periods in 2011. In both hydrological periods, we found a Clementsian pattern for active dispersers, with environment as the main structuring factor. The high environmental heterogeneity of this floodplain is an important factor providing high availability of favorable habitats for the establishment of active dispersers. Passive dispersers were randomly distributed in both hydrological periods. The importance of only spatial factors during the drought may indicate a restricted dispersal by inability of tracking environmental gradients. We emphasize that understanding biological community determinants could rely on trait-based analysis (i.e., dispersal mode) and complementary approaches (i.e., variance partitioning, and metacommunity structure), considering their variations over time.

Effect of habitat heterogeneity in the composition and distribution of Chironomidae (Diptera) assemblage in different microhabitats of preserved streams in the Brazilian Atlantic Forest

AIM: This study aimed at to evaluate the influence of habitat heterogeneity on the attributes of richness, abundance, diversity and equitability of Chironomidae assemblage and also the biological differences in faunistic composition related to each microhabitat. METHODS: The sampling was performed in summer (February) and winter (August) 2010, with Surber sampler, in three headwaters streams at Atlantic Forest, in southern Brazil. RESULTS: In the total 6,429 Chironomidae larvae were identified and classified into 96 taxa belonging to Chironominae, Tanypodinae and Ortocladiinae subfamilies. Among the microhabitats, the highest richness was observed in the deposits of litter, and the highest number of exclusive species took place in the pool regions. CONCLUSIONS: Thus, the composition and structure of the Chironomidae assemblage are directly related to the availability and heterogeneity of habitats in streams.

Chironomidae feeding habits in different habitats from a Neotropical floodplain: exploring patterns in aquatic food webs

Ecological studies on food webs have considerably increased in recent decades, especially in aquatic communities. Because Chironomidae family are highly specious, occurring in almost all aquatic habitats is considered organisms-key to initiate studies on ecological relationships and trophic webs. We tested the hypothesis that the diversity of the morphospecies diet reflects differences on both the food items available among habitats and the preferences of larval feeding. We analyzed the gut content of the seven most abundant Chironomidae morphospecies of the different habitats from the Upper Paraná River. We categorized the food items found into algae, fungal spores, fragments of plants, algae and animal fragments and sponge spicules. We observed the algae predominance in the gut content of morphospecies from lakes. Considering the different regions from each lake, we registered the highest food abundance in the littoral regions in relation to the central regions. From the variety of feeding habits (number of item kinds), we classified Chironomus strenzkei, Tanytarsus sp.1, Procladius sp.1 as generalist morphospecies. We found a nested pattern between food items and Chironomidae morphospecies, where some items were common to all taxa (e.g., Bacillariophyceae algae, especially), while others were found in specific morphospecies (e.g., animals fragments found in Procladius sp.1). The algae represented the most percentage of gut contents of Chironomidae larvae. This was especially true for the individuals from littoral regions, which is probably due to the major densities of algae associated to macrophytes, which are abundant in these regions. Therefore, the feeding behavior of these morphospecies was generalist and not selective, depending only of the available resources.

Benthic invertebrates nestedness in flood and drought periods in a Neotropical floodplain: looking for the richest environments

Aim Floodplains are among the most biologically diverse systems in the world, where hydrological regime is recognized as crucial to structure aquatic communities. We predicted that i) structure of benthic metacommunity is nested in the drought and random in the flood season in a Neotropical floodplain. We expected to find ii) environmental homogenization during the flood season which may disrupt the nested pattern. Moreover, we identified habitats of high taxa richness of benthic invertebrates and characterized them by habitat type and fluvial systems. Methods We sampled benthic invertebrates from 36 habitats in the Upper Parana River floodplain. We tested nestedness using NODF index and evaluated the environmental variability using the multivariate homogeneity of group dispersions (PERMDISP), separately for flood and drought periods. Results The environmental variability was lower during the flood. We found a nested distribution among benthic invertebrates in both flood and drought periods. The highest species richness values were recorded in small and unconnected lakes from Parana fluvial system and some rivers and secondary channels, independent of the fluvial system. Chironomidae, Oligochaeta and Ostracoda were the most frequent taxa and were recorded in all habitats. Conclusion The nested distribution of benthic invertebrates is a consistent pattern for this metacommunity because its distribution was not disrupted by floods that homogenize limnological conditions and increase the connectivity among habitats. We also found that habitats with high taxa richness were both lotic and lentic in the three fluvial systems. Our findings emphasize that different habitats in different subsystems sustains the richness of the benthic invertebrates metacommunity in the Upper Parana River floodplain over time.

Influência da heterogeneidade ambiental sobre os atributos da comunidade de Chironomidae em lagoas de inundação neotropicais

The environmental structure is an important factor influencing the communities distribution. In this context, physically more complex environments sustain higher species richness than those simpler. We aimed to evaluate the influence of environmental heterogeneity on the atributes of Chironomidae community, such that to determe their spatial distribution in different lakes from the Upper Parana River floodplain. Samples were collected quarterly from March to December 2011 in six environments (three lakes with connection and three lakes without connection to main river). We determined the lacustrine heterogeneity, by the Environmental Score of each lake, which was calculated by summing of chemical, physical and biological features of the lakes. The correlations between the environmental heterogeneity with the richness, density and diversity of chironomid species were significant. These results suggest that the lakes with the greatest environmental heterogeneity (or highest Environmental Score) are more able to support a higher number of individuals and taxa.

First records of Freshwater Bivalves of Ilha Grande National Park, Paraná, Brazil

The Ilha Grande National Park, Parana, Brazil, is located in the Upper Parana River and has characteristics typical of a floodplains. This protected area includes lagoons connected and disconnected to the Parana River, although the latter also connect during periods of high water level, thus composing a heterogeneous group of lacustrine environments. The enormous potential the flora and fauna diversities are still little known to the region, as can be seen through benthic invertebrates, inclunding bivalves mollusks. The granulometric composition of these floodplain lagoons was formed mainly by mud and very fine sand. Furthermore, organic matter composition was predominantly of fine particulate. The other abiotic factors differed from lagoons located within the island of the park to those located in the left margin of Parana River. The results demonstrated the importance of abiotic factors such as the physical composition of granulometric texture, organic matter and macrophyte banks, to the establishment of bivalves in these floodplain lagoons. We recorded bivalves of Pisidium (native), Diplodon (native), and Corbicula (invasive). The highest values of Diplodon sp. density were observed at Sao Joao/C lake, for Pisidium sterkianum (Pilsbry, 1897) at Sao Joao/M lake, and to Jatoba/C lagoon with high density of invasive species Corbicula fluminea (Muller, 1774). This study to obtain conduct the first records of freshwater bivalves in floodplains lagoon in the Ilha Grande National Park, and provides contributions to better understanding the ecology of these mollusks. The recording of native species in the region of Upper Parana River floodplain after a lomg period without new records, demonstrated the importance of protecting the lagoons of the Ilha Grande National Park as they can be a possible refuge to some species of native freshwater bivalves.

Extreme drought events can promote homogenization of benthic macroinvertebrate assemblages in a floodplain pond in Brazil

Extreme weathers tend to become frequent following global warming and may promote important changes in species composition. We used benthic macroinvertebrates to test the hypothesis that extreme drought events could lead to local biotic homogenization in a floodplain pond. We took sediment samples in three sampling areas of a floodplain pond during a period of the usual hydrological cycle and during an extreme weather event that caused an atypical hydrological cycle with prolonged drought period. We found that community composition significantly differs between usual hydrological cycle and extreme drought periods, in which only species adapted to unfavorable environmental conditions remained. The spatial beta diversity decreased during the extreme drought periods, presenting lower variability compared to the usual hydrological cycle. However, species density, richness, and diversity increased during the droughts. We expect that, in scenarios of climate change with frequent extreme weathers, droughts may cause permanent negative impacts on aquatic communities, leading to biotic homogenization. Moreover, our findings indicate that prolonged droughts could increase the time needed to community recovery, suggesting lower community resilience to environmental stressors. Therefore, increasing frequency of extreme drought events may result in an alternative community structure.

Correction to: Extreme drought events can promote homogenization of benthic macroinvertebrate assemblages in a floodplain pond in Brazil

Due to an unfortunate turn of events, the surname of the first author appeared incorrectly in the original publication as it should have read A. P. S. Bertoncin. The original article has been corrected and the proper representation of the authors’ names and their affiliation is also listed here. We apologize to the authors and readers for the inconvenience.