Heloísa Evangelista | Universidade Estadual de Maringa (original) (raw)

Papers by Heloísa Evangelista

Aquatic Sciences, 2021

Diverse communities are more productive than less diverse ones because of two overyielding mechan... more Diverse communities are more productive than less diverse ones because of two overyielding mechanisms: a selection effect and a complementarity effect, which operate in different ways. Moreover, ecosystem multifunctionality is expected to increase and become more stable with increasing species diversity. However, it is unclear how the aforementioned processes operate in aquatic ecosystems, where the overyielding mechanisms, ecosystem multifunctionality, and stability have been poorly explored. Here, we conducted an experimental study manipulating three levels of macrophyte richness to test two hypotheses: (i) the positive macrophyte richness effect on community biomass production is the result of the species complementarity effect; (ii) ecosystem multifunctionality and its stability increase with macrophyte richness. We found that macrophyte species increased their biomass production in high richness treatment, evidencing overyielding, which occurred through a significant complementarity effect. Macrophyte richness also enhanced ecosystem multifunctionality, and made it more stable over time, but only in high richness treatment. Our study shows that preserving high macrophyte richness is essential to preserving the ability of aquatic communities and ecosystems to sustain their functioning.

Aquatic Biology, 2012

Hydrilla verticillata is an aquatic macrophyte recently found in the Upper Paraná River floodplai... more Hydrilla verticillata is an aquatic macrophyte recently found in the Upper Paraná River floodplain. This species has a high potential to reproduce and disperse to new sites, mainly through stem fragments. In this study, we evaluated the colonization (the ability of roots to develop), regeneration (the ability of lateral shoots to develop) and growth rates of this species using fragments of different lengths that originated from different plant parts. We selected parts with and without apical tips, each 5 and 10 cm long, and the following hypothesis was tested: the fragments with apical tips have greater colonization and regeneration abilities than fragments without apical tips, and these abilities depend on the fragment length. Our results showed that both fragments with and without tips presented the same number and dry weight of roots and shoots and thus did not differ in their colonization or regeneration abilities. The length was important for the colonization ability, as 10 cm fragments produced more roots than 5 cm fragments. The high colonization and regeneration abilities from different fragments coupled with the high growth rates exhibited by H. verticillata may account for its rapid spread in novel habitats and its competitive success over native species. Thus, we suggest that the inadequate management of this species, resulting in the formation of fragments, especially of large lengths, may have important implications with regard to its infestation of new sites.

As áreas de transição entre os ecossistemas aquáticos e terrestres da planície de inundação do al... more As áreas de transição entre os ecossistemas aquáticos e terrestres da planície de inundação do alto rio Paraná são cobertas por extensos campos naturais, onde várias espécies de gramíneas dominam. No presente trabalho, foram medidas as taxas de produção primária de Paspalum sp, em áreas localizadas na várzea do rio Ivinheima e do rio Baía (alto rio Paraná). O método empregado baseou-se em medidas de alteração temporal de biomassa viva, morta e das taxas de decomposição. As medidas de produção encontram-se dentro do espectro de valores encontrados em outras áreas alagáveis do Brasil. Não houve efeito significativo dos locais de coleta sobre as taxas de produção primária, mas o tempo afetou de forma significativa esse processo na várzea do rio Ivinheima. A semelhança dos resultados entre as áreas investigadas sugere um grande potencial de extrapolação dos resultados para a planície, possibilitando sua utilização em modelos de fluxo de energia nesse trecho do rio Paraná.

Aquatic Invasions, 2014

In this study, we performed a scientometric analysis of published scientific papers on the biolog... more In this study, we performed a scientometric analysis of published scientific papers on the biological invasion of macrophytes in freshwater ecosystems to assess the main trends and gaps in research concerning this group of organisms. The analysis showed that publications on invasive macrophytes increased exponentially in the last decade. However, the activity index (a comparison of the quantitative trends of invasive macrophytes in relation to all of the papers on macrophytes) indicated that invasive macrophytes have not been consistently studied more than other topics in the field of limnology over the last decade. The most studied macrophyte species were Myriophyllum spicatum, Hydrilla verticillata, Phragmites australis and Eichhornia crassipes. Certain gaps were related to the limited number of studies on the important species threatening tropical ecosystems, under-representation of investigations on the impacts of invasive macrophytes on fish and lack of studies associating macrophytes with microorganisms (bacteria and fungi). Studies that encompassed several levels of biological complexity were also scarce, indicating that the studies were fragmented at specific levels. Finally, there was a clear geographical bias, with fewer studies occurring in Neotropical and Afrotropical regions. Identification of these gaps may be useful for addressing future studies that might help evaluate the causes of invasion by macrophytes and the impacts of such invasions on freshwater ecosystems.

Brazilian Journal of Physics, 2009

A family of entropy indices constructed in the framework of Tsallis entropy formalism is used to ... more A family of entropy indices constructed in the framework of Tsallis entropy formalism is used to investigate ecological diversity. It represents a new perspective in ecology because a simple equation can incorporate all aspects of α−diversity, from richness to dominance and can be also related to a measure of species rarity. In addition, a generalized Kullback-Leibler distance, constructed in the framework of a nonextensive formalism, is recalled and used as a measure of β−diversity between two systems. These tools are applied to data relative to the macrophytes collected from two not far apart arms of Itaipu Reservoir, in Paraná River basin.

Brazilian Archives of Biology and Technology, 2012

In this work, a recently proposed diversity index based on Patil and Taillie parametric diversity... more In this work, a recently proposed diversity index based on Patil and Taillie parametric diversity measure (or Tsallis entropy), S q* , was applied to samples (presence-absence data) of macrophytes from the Itaipu Reservoir, Brazil. This new index was the value of the family of indices S q for a specific evenness of a sample. Results demonstrated that the Shannon index and species richness showed expressively high correlation with the S q* ; however, the evenness had low correlation coefficients with the index S q* , indicating that S q* was particularly sensitive to rarity and species richness. On the other hand, the weak correlations of this index with evenness demonstrated that it was less sensitive to species relative abundances.

Aquatic Ecology, 2012

The propagation of most aquatic macrophytes occurs vegetatively, via fragments. After dispersal, ... more The propagation of most aquatic macrophytes occurs vegetatively, via fragments. After dispersal, the fragments may exhibit two survival strategies: colonization (the ability to develop roots) and regeneration (the ability to develop new propagules that can disperse). Invasive species, for example, Hydrilla verticillata, are known to have a high potential for dispersal and growth. We experimentally evaluated the colonization and regeneration abilities and growth rates of this species in the early stage of development and compared these properties to the corresponding characteristics of two native species of Hydrocharitaceae (Egeria densa and Egeria najas). The following hypotheses were tested: (1) fragments with apical tips have greater colonization and regeneration abilities and higher growth rates than fragments without apical tips and (2) H. verticillata has greater colonization and regeneration abilities and higher growth rates than other native species of Hydrocharitaceae. Our results showed that both types of fragments had the same ability to colonize, whereas fragments without tips had a higher ability to regenerate. However, fragments with apical tips showed higher growth rates. It is probable that these higher growth rates resulted from apical dominance. H. verticillata had the greatest propagation potential. Its colonization and regeneration abilities and growth rates were greater than those of the native species. These differences can produce competitive advantages for the exotic species in the early stages of development in new habitats and may contribute to understanding the success of the exotic compared to the native species.

Acta Limnol. Bras, 2009

Abstract: Aim: In this study, we used multiple statistical protocols to evaluate which nutrient c... more Abstract: Aim: In this study, we used multiple statistical protocols to evaluate which nutrient content best explains senescent macrophyte and detritus decomposition of several macrophyte species in a lake of the Upper Paraná River floodplain; Methods: Senescent macrophytes of different life forms were left to decompose in litter bags. Macrophyte nutrient contents were quantified before and after incubation. Simple regressions, multiple regressions and Akaike information criterion were used to evaluate which nutrient best ...

Journal of Applied Ecology, 2016

1. Riparian corridors are habitats that are prone to invasion by non-native plants, but the shade... more 1. Riparian corridors are habitats that are prone to invasion by non-native plants, but the shade provided by trees that grow in riparian zones may limit the success of invasive species. 2. In this investigation, we conducted three complementary experiments to test the effects of shade levels, along with sediment type and biotic resistance (and their interactions), on the establishment of a highly invasive grass (Urochloa arrecta (Hack. ex T. Durand & Schinz) Morrone & Zuloaga). 3. This invasive grass presented higher growth rates in sediment collected under riparian vegetation than in sediment collected at the sites devoid of vegetation. Shade levels similar to those found underneath riparian vegetation suppressed the establishment of U. arrecta. In addition, when native macrophytes were planted a priori (i.e. before U. arrecta propagules arrived), the establishment of the invasive species was suppressed, even at lower levels of shade. Thus, biotic resistance was sufficient to prevent the establishment of the invasive grass at low shade levels. Therefore, our results indicated that although the sediment from riparian zones may favour the establishment of U. arrecta, shading by trees and the presence of native macrophytes suppress it. 4. Synthesis and applications. Our results indicate that the shade provided by riparian trees and biotic resistance by macrophytes are likely the factors that negatively affect the establishment of the invasive macrophyte Urochloa arrecta. A recommendation for management arising from our results is that restoring riparian corridors to prevent invasion is most likely more efficient if native macrophytes are planted along with the trees. This would be an efficient strategy to prevent invasion by U. arrecta and other invasive Poaceae during the early stages of riparian vegetation regeneration.

Aim: In this study, we used multiple statistical protocols to evaluate which nutrient content bes... more Aim: In this study, we used multiple statistical protocols to evaluate which nutrient content best explains senescent macrophyte and detritus decomposition of several macrophyte species in a lake of the Upper Paraná River floodplain; Methods: Senescent macrophytes of different life forms were left to decompose in litter bags. Macrophyte nutrient contents were quantified before and after incubation. Simple regressions, multiple regressions and Akaike information criterion were used to evaluate which nutrient best explained initial macrophyte decomposition and the decomposition of detritus that was partially decomposed. In addition, multi-model inference was used to generate models that explained decomposition rates; Results: The results showed that initial concentrations of phosphorus and carbon are the best predictors of decomposition rates of senescent tissues. When we evaluated the decomposition of partially decomposed detritus, the nitrogen content assumed an important role in determining decomposition rates. However, all candidate models had high explanatory strength; Conclusions: We argue that multi-model inference is a powerful strategy for explaining the impact of nutrient quality on macrophyte decomposition in the Upper Paraná River floodplain.

Hydrilla verticillata recently invaded a protected area in the Upper Paraná River floodplain. In ... more Hydrilla verticillata recently invaded a protected area in the Upper Paraná River floodplain. In a rare opportunity, when this non-indigenous species co-occurred with the native Egeria najas in a secondary channel of the river, we assessed its effects on assemblage of small-sized fish. Traps were used to catch fish inside macrophyte patches in periods of low and high water. We assessed fish abundance, biomass, diversity, richness and the community composition (using a DCA). The number of fish species did not differ between plants. Fish abundance and biomass were significantly higher during the low water period but plant species did not affect these attributes. Similarly, fish assemblage composition differed only between seasons. Our results indicate that the oscillations in the water level had a greater effect on the small-sized fish assemblage than the presence of the non-indigenous macrophyte. In addition, H. verticillata favors small fish assemblages such as the native does; however, we contend that our conclusions are valid only for habitats scarcely colonized by native plant species. The invasion of other habitats colonized by a high diversity of native species of macrophytes, which are key for small-sized fish, is a matter of concern.