Joana Darc Batista

Community assembly of adult odonates in tropical streams: an ecophysiological hypothesis.

Community assembly theory is founded on the premise that the relative importance of local environmental processes and dispersal shapes the compositional structure of metacommunities. The species sorting model predicts that assemblages are dominated by the environmental filtering of species that are readily able to disperse to suitable sites. We propose an ecophysiological hypothesis (EH) for the mechanism underlying the organization of species-sorting odonate metacommunities based on the interplay of thermoregulation, body size and the degree of sunlight availability in small-to-medium tropical streams. Due to thermoregulatory restrictions, the EH predicts (i) that larger species are disfavored in small streams and (ii) that streams exhibit a nested compositional pattern characterized by species’ size distribution. To test the EH, we evaluate the longitudinal distribution of adult Odonata at 19 sites in 1st- to 6th-order streams in the Tropical Cerrado of Brazil. With increasing channel width, the total abundance and species richness of Anisoptera increased, while the abundance of Zygoptera decreased. The first axis of an ordination analysis of the species abundance data was directly related to channel width. Mean and maximum thorax size are positively correlated to channel width, but no relationship was found for the minimum thorax size, suggesting that there is no lower size constraint on the occurrence of these species. Additionally, a nested compositional pattern related to body size was observed. Our results support the EH and its use as an ecological assembly rule based on abiotic factors. Forest cover functions as a filter to determine which species successfully colonize a given site within a metacommunity. As a consequence, the EH also indicates higher treats for small-bodied zygopterans in relation to the loss of riparian forests in tropical streams.

Baetidae (insecta: ephemeroptera) de nova xavantina, Mato Grosso, Brasil: novos registros e descrição de uma nova espécie de cloeodes traver

Studies carried mainly in the municipality of Nova Xavantina, Mato Grosso State, have lead us to the discovery of several species of Baetidae. While one of them represents a new species of the genus Cloeodes and is herein described, the others represent new records for the state or even for Brazil. The new species, Cloeodes auwe sp. nov., can be differentiated from the other known species of the genus by the following characteristics: body color pattern, long and two-segmented maxillary palp, third segment of labial palp robust and apically truncate, long tarsal claws (0.5 times the length of the respective tarsus), hind wing pads absent, and number of spines on the posterior margin of the third tergite and on the paraproct. Besides this new species, the following taxa of Baetidae were also found: Adebrotus amazonicus, Americabaetis alphus, Apobaetis sp., Aturbina georgei, Baetodes sp., Callibaetis sp.1, Callibaetis sp.2, Camelobaetidius janae, Cryptonympha sp., Harpagobaetis gulosus, Paracloeodes binodulus, Spiritiops silvudus, Waltzoyphius fasciatus, and Zelusia principalis.

Longitudinal Distribution of the Functional Feeding Groups of Aquatic Insects in Streams of the Brazilian Cerrado Savanna.

We demonstrate that the distribution of the functional feeding groups of aquatic insects is related to hierarchical patch dynamics. Patches are sites with unique environmental and functional characteristics that are discontinuously distributed in time and space within a lotic system. This distribution predicts that the occurrence of species will be based predominantly on their environmental requirements. We sampled three streams within the same drainage basin in the Brazilian Cerrado savanna, focusing on waterfalls and associated habitats (upstream, downstream), representing different functional zones. We collected 2,636 specimens representing six functional feeding groups (FFGs): brushers, collector–gatherers, collector–filterers, shredders, predators, and scrapers. The frequency of occurrence of these groups varied significantly among environments. This variation appeared to be related to the distinct characteristics of the different habitat patches, which led us to infer that the hierarchical patch dynamics model can best explain the distribution of functional feeding groups in minor lotic environments, such as waterfalls.

Effects of environmental factors on community structure of Leptophlebiidae (Insecta, Ephemeroptera) in Cerrado streams, Brazil

O efeito de fatores ambientais sobre a abundância, riqueza de especies e grupos funcionais alimentares de Leptophlebiidae foi analisado em 16 locais pertencentes a quatro corregos de Cerrado, a partir de coletas de substrato em tres periodos de 2005. Foram amostradas 5.492 larvas distribuidas em 14 especies, classificadas em tres grupos funcionais alimentares: raspadores, coletores-filtradores e fragmentadores. A abundância e riqueza de especies nao foram afetadas por nenhum dos fatores ambientais investigados, mas a integridade dos habitats exerceu efeito positivo sobre a abundância dos fragmentadores, consequencia da intrinseca interacao desses organismos com a mata ciliar. Dessa forma, acreditamos que este trabalho agrega informacoes bioecologicas sobre as especies e grupos funcionais de insetos aquaticos e podera contribuir no monitoramento e conservacao de riachos do Cerrado.

Taxonomic and Numerical Resolutions of Nepomorpha (Insecta: Heteroptera) in Cerrado Streams

Transformations of natural landscapes and their biodiversity have become increasingly dramatic and intense, creating a demand for rapid and inexpensive methods to assess and monitor ecosystems, especially the most vulnerable ones, such as aquatic systems. The speed with which surveys can collect, identify, and describe ecological patterns is much slower than that of the loss of biodiversity. Thus, there is a tendency for higher-level taxonomic identification to be used, a practice that is justified by factors such as the cost-benefit ratio, and the lack of taxonomists and reliable information on species distributions and diversity. However, most of these studies do not evaluate the degree of representativeness obtained by different taxonomic resolutions. Given this demand, the present study aims to investigate the congruence between species-level and genus-level data for the infraorder Nepomorpha, based on taxonomic and numerical resolutions. We collected specimens of aquatic Nepomorpha from five streams of first to fourth order of magnitude in the Pindaíba River Basin in the Cerrado of the state of Mato Grosso, Brazil, totaling 20 sites. A principal coordinates analysis (PCoA) applied to the data indicated that species-level and genus-level abundances were relatively similar (>80% similarity), although this similarity was reduced when compared with the presence/absence of genera (R = 0.77). The presence/absence ordinations of species and genera were similar to those recorded for their abundances (R = 0.95 and R = 0.74, respectively). The results indicate that analyses at the genus level may be used instead of species, given a loss of information of 11 to 19%, although congruence is higher when using abundance data instead of presence/absence. This analysis confirms that the use of the genus level data is a safe shortcut for environmental monitoring studies, although this approach must be treated with caution when the objectives include conservation actions, and faunal complementarity and/or inventories.

Does the damming of streams in the southern Amazon basin affect dragonfly and damselfly assemblages (Odonata: Insecta)? A preliminary study

Our goal was to investigate whether the loss of riparian forests alters the structure of assemblages and populations of dragonflies and damselflies. We tested the hypothesis that the composition of the odonate assemblages found upstream from dams are significantly different from those found downstream of these barriers. To test the hypothesis, we investigated stream sectors upstream and downstream of three dams located at the extreme of the southern Amazon basin, in the Brazilian state of Mato Grosso. We collected 111 adult odonates, 45 upstream and 69 downstream, representing 18 species, 12 upstream and 10 downstream. The most abundant species was Epipleoneura williamsoni Santos, 1957 (n = 41, 36.9%), followed by Epipleoneura metallica Rácenis, 1955 (n = 20, 18%) and Hetaerina curvicauda Garrison, 1990 (n = 17, 15.3%). Statistical ordination separated the different sectors, with the greatest dissimilarity being found between the upstream and downstream I (DS I), and our hypothesis was further supported by the fact that six of the 18 species recorded in the study did not occur in the upstream sector. As this process may lead to the local extinction of part of the biodiversity of the Amazon–Cerrado transition, even before it is fully understood, we would recommend that the observed pattern be verified through the analysis of other taxonomic groups and on a more ample spatial scale.

Odonata (Insecta) from Nova Xavantina, Mato Grosso, Central Brazil: Information on species distribution and new records

Odonates are found in all freshwater environments, and are specially species rich in tropical freshwater ecosystems. Currently about 800 odonate species are known to Brazil, but only 29% of the Brazil territory have been surveyed for this group. Here we provide a species list with information on distribution and new records for Odonata in nine streams in Nova Xavantina, Mato Grosso, Central Brazil. We used the scan procedure with a fixed area for three days in each stream between 10:00 and 14:00h. We collected 1038 dragonfly specimens belonging to 67 species, which represents 8% of the known Brazil odonate fauna. Additionally, five new records for the study area are presented.

Mayfly assemblage structure of the Pantanal Mortes–Araguaia flood plain

The diversity of lakes, rivers and streams of flood plain sustains great taxonomic and functional diversity. The Bananal flood plain is located mainly in the State of Mato Grosso, in the southern region of the Cerrado Biome and north of the Cerrado–Amazonia transition zone, two very diverse ecosystems. In the present study, to test the hypothesis that composition, richness and functional groups would differ between regions (south and north), as well as between environments (lentic and lotic), always being greater in the northern area and in lotic environments, immature Ephemeroptera individuals were collected from 12 aquatic environments, 6 streams and 6 lakes, in the northern and southern regions of the plains. Composition differed only between regions; the richness of genera and the number of functional feeding groups was higher in the northern region, and did not differ between environments. The greater diversity in the northern region may be because of its location in the ecotone of two highly diverse ecosystems, whereas the similarity between the lentic and lotic environments may be because of the homogenisation temporarily caused by floods during the flood period, increasing fluvial connectivity. Knowledge of the diversity patterns in these inhospitable regions spatially minimises knowledge gaps and provides empirical evidence of the importance of areas such as the Cerrado–Amazon transition for conservation, as shown in the present study.