Leonardo Maltchik

Environmental Factors as Predictors of Aquatic Macrophyte Richness and Composition in Wetlands of Southern Brazil

The main goal of this study was to determine how much variation in macrophyte richness and composition is explained by wetland area, altitude, water conductivity, and nitrate and total phosphorus concentrations in wetlands in southern Brazil, and to compare these variations in two wetland subsystems (palustrine and lacustrine). A total of 126 wetlands were sampled distributed in two subsystems: 87 palustrine and 39 lacustrine wetlands. A total of 153 species of aquatic macrophytes was found in wetlands of southern Brazil and the mean number of macrophyte species per site was 8.7 (range 1–23). From the variables tested, the altitude and area were the only predictor of macrophyte richness and explained 23.1% of variation in richness. The two first axes generated by CCA explained only 4.4% of the variation in the aquatic macrophytes distribution. The macrophyte richness was similar across lacustrine and palustrine subsystems. While altitude, area and conductivity explained 33.2% of variation in macrophyte richness in the palustrine subsystem, none of the variables were associated with macrophyte richness in the studied lacustrine wetlands.

Influence of area, habitat and water chemistry on richness and composition of macrophyte assemblages in southern Brazilian wetlands

Abstract Questions: Two hypotheses were tested: (1) physical features, such as wetland surface area and habitat diversity, together with water chemistry, are important determinants of species richness and composition of macrophyte assemblages and (2) species richness and composition of macrophyte assemblages differ between wetlands of different types (i.e., palustrine versus lacustrine) and between wetlands of different hydrologies (i.e. permanent versus intermittent). Location: A subtropical coastal plain segment (2500 km2) of southern Brazil. Methods: Quarterly collections were carried out in 15 wetlands (2004–2005) in southern Brazil. Differences in richness over time were tested using repeated measures ANOVA. Stepwise multiple regression was performed to investigate relationships between total richness and environmental variables. Significance of differences between wetland types and hydroperiods on species composition was verified by MRPP (Multi-Response Permutation Procedure). The influence of the environmental variables on species composition was assessed using CCA (Canonical Correspondence Analysis). Results: Macrophyte species richness changed with time, was not significantly different between wetland types, but was higher in permanent wetlands than in intermittent ones. Area, habitat diversity and soluble reactive phosphorus concentration explained 76% of the variation in species richness. Species composition was different between permanent and intermittent wetlands, although it was not significantly different between wetland types. Area, habitat diversity and water chemistry explained 50.1% of species composition. Conclusions: Species richness and composition of wetland macrophytes were mainly determined by area, habitat diversity and hydroperiod. These results can be used for the development of conservation and management programs in southern Brazil. Nomenclature: Irgang & Gastal (1996).

Spatial and Temporal Patterns of Waterbird Assemblages in Fragmented Wetlands of Southern Brazil

Abstract Understanding the composition and abundance pattern of species across sites is a central question in community ecology. However, the structure of waterbird assemblages in fragmented wetlands has been poorly documented. We carried out twelve monthly censuses to describe the composition and abundance patterns in 42 wetland fragments and two lagoons in the coastal zone of Rio Grande do Sul, South Brazil. A total of 142,000 birds from 66 species, 18 families and 18 orders were recorded. Most species were either resident (29) or partial migrants (19). All migrant species (8 nearctic, 4 austral and 5 summer breeders) were recorded in small numbers and most of them were restricted to lagoons. The lagoons had more species (60) than the wetland fragments (55), even though the total fragment area (1,426 ha) was about twice the censed area in the lagoons (743 ha). Principal Coordinate Analysis revealed strong temporal and spatial gradients of abundance and composition that were similar in fragments and lagoons. The number of species varied among sites and showed no seasonal pattern. Abundances were higher in the wintering period (min. of 2,500 birds in March and max. of 23,000 in July) due to the increased abundance of Gruiformes and Anseriformes. The White-faced Whistling-duck (Dendrocygna viduata) and the Common Moorhen (Gallinula chloropus) were the most abundant and frequent species over the year, comprising together 69% of the total. The census captured 76% and 60% of the waterbird species listed for the region and the Rio Grande do Sul State, respectively. The study area shared more than 90% of the species with the nearby States and 76% with the Pantanal region. The beta-diversity among sites was 94% when only fragments are considered, and 38% when the lagoons are included in the calculation, showing that a great proportion of the waterbird richness at the landscape scale is accommodated as a beta component. The local abundance and composition of waterbird assemblages seemed to be affected by the interplay of several factors, including the rich regional pool of species, their wide range, the fragment area, the surrounding matrix and the presence of core refuges. A landscape perspective is essential on building sound conservation programs for waterbird assemblages.

Effects of hydrological variation on the aquatic plant community in a floodplain palustrine wetland of southern Brazil

This study analyzed macrophyte richness, biomass, and composition under flooding of brief duration (less than 3 days) and drawdown events over an annual cycle in a floodplain palustrine wetland in the south of Brazil. The study was carried out to test the hypothesis that floods of brief and very brief duration are not long enough to compromise the richness and the biomass of aquatic macrophytes and that the alternation between wet and drawdown phases may cause variations in the macrophyte richness and composition. A total of 26 aquatic macrophyte species were observed from April 2003 to May 2004: 13 species were observed during the wet phase, and 24 during the drawdown phase. The mean richness was higher during the drawdown phase than during the wet phase, however, the mean biomass was similar in both phases. Although macrophyte richness was not modified after the three flooding events, mean biomass was modified after two events. The number of macrophyte species of which the biomass was modified after the first flooding event increased with subsequent floods. These results illustrate the importance of the dynamics between brief floods and drawdown events to the aquatic plant community in floodplain wetlands in southern Brazil.

Environmental predictors of macroinvertebrate communities in coastal wetlands of southern Brazil

The rapid degradation of wetlands worldwide accentuates the urgent need for ecological data to help manage and protect the threatened biodiversity in the remaining often-fragmented wetlands. In the Neotropics where fragmentation is common, environmental factors structuring aquatic macroinvertebrate communities are poorly known. We tested the hypothesis that physical features, such as wetland area, habitat diversity, water depth and temperature, and water and sediment chemistry are important correlates with richness, density and composition of wetland macroinvertebrate assemblages in Brazil. If so, do these correlations differ between summer and winter? A total of 16 895 individuals across 61 families were collected. Richness was positively associated with habitat diversity and water depth and negatively associated with water temperature. Macroinvertebrate density was negatively associated with water depth, and positively correlated with habitat diversity, percentage of sediment organic matter and water conductivity. Macroinvertebrate composition was associated mainly with wetland area and habitat diversity in the wetlands studied; these relationships persisted in both seasons. Our data illustrate environmental factors that potentially structure and maintain aquatic macroinvertebrate biodiversity in southern Brazil wetlands, and should be managed because 90% of these ecosystems have already been lost as a result of human activities.

Influence of area, altitude and hydroperiod on macroinvertebrate communities in southern Brazil wetlands

Wetlands are important ecosystems in southern Brazil because they show high productivity and biological diversity. However, conservative data indicate that ~90% of the wetlands have disappeared as a result of agricultural expansion. In this sense, the understanding of species composition and richness patterns in fragmented and natural wetlands is a priority for biodiversity conservation strategies. The main goal of the present study was to determine how much variation in macroinvertebrate richness and composition is explained by wetland area, hydroperiod and altitude. This survey was carried out in an extensive area of the Neotropical region (~280000 km2 – southern Brazil) with a large number of wetland systems (72) and covering a wide gradient of altitude and wetland surface area. The macroinvertebrate richness was higher in permanent wetlands than intermittent ones, and intermittent wetlands supported a macroinvertebrate composition that clearly differed from those of permanent wetlands. Macroinvertebrate richness was positively affected by wetland area; however, this relationship was significant only in permanent wetlands. There is a need to promote conservation of all wetland systems in southern Brazil, regardless of their hydroperiod and area. These arguments are essential to develop conservation and management programs of wetlands in this region.

Species-area relationship and environmental predictors of fish communities in coastal freshwater wetlands of southern Brazil

In the Neotropics where fragmentation is common, environmental factors structuring fish communities are poorly known. In this study two hypotheses were tested in 13 coastal wetlands of southern Brazil: 1) physical features (such as wetland area, habitat diversity, water depth and temperature, and water and sediment chemistry) are important determinants of richness, density and composition of fish assemblages; and 2) species richness and composition of fish assemblages differ between wetlands with different hydroperiods (i.e. permanent versus intermittent). A total of 1,597 individuals distributed among 20 species were collected. Richness was positively associated with wetland area and water depth and it was negatively associated with water conductivity. The species-area power function explained 27.3% of the variation in richness. Fish richness was similar between permanent and intermittent wetlands. The density was negatively associated with water depth and temperature, and it was positively correlated with water nitrate concentration. The first three axes from the CCA accounted for 55.5% of total variation in fish composition. The most important variables related to fish composition were percentage of sediment organic matter, phosphorus concentration, habitat diversity and water depth. Composition of fish species changed among permanent and intermittent wetlands. Understanding the environmental factors that shape and maintain the biodiversity in these ecosystems is essential to develop conservation and management programs of wetlands in this region, where more than 90% of wetland systems have already been lost due to anthropogenic activities.

Factors influencing anuran distribution in coastal dune wetlands in southern Brazil

We investigated the potential role of hydroperiod and habitat structural complexity as explanatory factors defining richness, abundance and spatial and temporal distribution of anurans in wetlands of coastal dunes. This survey was performed in 15 wetlands along the Atlantic coastal zone of southern Brazil. We identified 10 anuran species (nine in the adult and eight in the tadpole stage) distributed in seven genera from five families. The adult richness and abundance varied among the hydroperiod classes, but without temporal variations. Both tadpole richness and abundance varied temporally and both were influenced by hydroperiod. Adult anuran composition was associated with dry months and wetland area, whereas tadpole composition was associated with emergent and floating macrophytes, wetland area and vegetation cover. This study identified the importance of habitat structural complexity and hydroperiod in spatial–temporal distribution models of anurans.

Check-list of diversity of anurans in Rio Grande do Sul (Brazil) and a classification propose for larvals forms

As ocorrencias de novas especies de anuros, aliadas as recentes revisoes taxonomicas de diversos generos, estimulam a elaboracao de uma atualizacao na lista de especies de anuros ( check-list ) para o Rio Grande do Sul. Essas informacoes sao valiosas para o conhecimento de sua diversidade, principalmente quando se trata de um grupo tao ameacado de extincao. O conhecimento sobre a diversidade biologica de anuros poderia ser maior se houvesse mais estudos realizados sobre seus estagios larvais. A utilizacao de uma chave de identificacao de girinos para o estado pode contribuir muito para o conhecimento dessa diversidade. Nesse sentido, os objetivos desse estudo foram elaborar uma lista atualizada das especies de anuros para o RS com informacoes sobre a descricao das formas larvais e elaborar a primeira chave artificial de identificacao de girinos baseada nas caracteristicas morfologicas externas. Atualmente, conhecem-se 84 especies de anuros para o RS, distribuidos em dez familias, das quais 50 possuem suas larvas conhecidas, sendo a maior parte larvas exotroficas aquaticas (47 spp.). Porem, somente cinco especies foram descritas baseada em populacoes do estado. Com a reuniao das informacoes sobre as especies e a caracterizacao de suas larvas, espera-se atenuar o esparso conhecimento sobre a anurofauna no Rio Grande do Sul. A chave de identificacao apresentada e um primeiro esforco no sentido de auxiliar trabalhos de monitoramentos e impactos ambientais, alem de estudos academicos. Palavras-chave: levantamento da biodiversidade, Anura, girino, regiao Neotropical.

Responses of freshwater molluscs to environmental factors in Southern Brazil wetlands

Freshwater molluscs play an important role in aquatic ecosystems, providing food for many fish species and vertebrates. Investigations on factors that determine mollusc species richness and distribution in wetland systems are scarce in the Neotropical region. The main goal of this study was to determine how much variation in mollusc richness and composition is explained by area, hydroperiod, altitude, water conductivity, and dominant aquatic vegetation. This survey was performed in an extensive area of a Neotropical region (approximately 280,000 km(2) in southern Brazil), with a large number of wetland systems (111) and covering a wide gradient of altitude and wetland surface area. The mollusc richness was positively associated with wetland area and negatively associated with altitude. The richness and composition of the freshwater molluscs were similar between permanent and intermittent wetlands and it did not differ significantly between aquatic bed and emergent wetlands. The first three axes of CCA explained 16.2% of the total variation in the composition of the freshwater mollusc observed. The variation in the composition had a correlation with wetland area, altitude and water conductivity. Our results showed that the wetlands are important habitats for molluscs in southern Brazil, and that the richness and the composition of molluscs were associated with area, altitude, water conductivity and dominant vegetation.