Eduardo R Cunha | Universidade Estadual de Maringa (original) (raw)

Papers by Eduardo R Cunha

We investigated the potential effects of an invasive alien Poaceae (Urochloa arrecta) on the abun... more We investigated the potential effects of an invasive alien Poaceae (Urochloa arrecta) on the abundance, richness, and composition of native macrophytes and fish. Samples were collected in patches of macrophytes dominated by the invasive species and in others dominated by a native macrophyte (Eichhornia azurea). We assessed the potential effects of these two species on macrophyte and fish abundance and richness, as well as in fish assemblage composition. The effects of both macrophytes did not differ when they were in similar, low bio-masses. Consistent with our expectations, however, the abundance of native macrophytes and fish decreased with increasing U. arrecta biomass, and both assemblages were eliminated at the extreme high levels of biomass attained by this species. In contrast, E. azurea did not affect the assemblages because this native species never reached levels of biomass as high as those recorded for the invasive species. Competition for space and light most likely determines the elimination of macrophytes in patches that are extensively colonized by U. ar-recta, whereas fish assemblages do not occupy these patches due most likely to the limited space available for movement and foraging. Thus, U. arrecta is a source of concern for biodiversity conservation because it has negative influences on both assemblages when it is well developed, which is true in the later stages of the invasion process. Abstract in Portuguese is available in the online version of this article

Natureza & Conservação, 2014

Paraná River A B S T R A C T Several species of aquatic macrophytes have invaded ecosystems outsi... more Paraná River A B S T R A C T Several species of aquatic macrophytes have invaded ecosystems outside their ranges, producing a variety of impacts on native biota. In this study, we tested the role of the invasive macrophyte Hydrilla verticillata as a foraging habitat for small fish species. To achieve this goal, we assessed the feeding activity and diet composition of fish captured in patches of the invasive H. verticillata and of a similar native macrophyte (Egeria najas). Feeding activity did not differ significantly between H. verticillata and E. najas, indicating that foraging activity was not affected. However, differences in diet composition were significant in three out of five fish species and marginally significant in one species, suggesting that the invasive and native macrophytes provide different types of food resources for fish. Thus, although H. verticillata does not affect the foraging activity, it has the potential to affect the assemblages of small-sized fish through changes in the proportions of food resources.

Fish species distribution is commonly influenced by aquatic macrophytes. Despite of the usage of ... more Fish species distribution is commonly influenced by aquatic macrophytes. Despite of the usage of these plants as habitats for refuge, feeding and reproduction by fish, too dense macrophyte stands make microhabitats unsuitable for certain fish species. Moreover, the distance from the open water within macrophyte stands may also affect fish species distribution because of increasingly harsh conditions. In order to test differences in species distribution of small-sized fish within macrophyte stands we sampled stands of Eichhornia spp presenting low and high levels of macrophyte density and at several distances from the open water (0, 3, 6, 9, 12 and 15 m). We measured depth, temperature, dissolved oxygen, conductivity and pH of the water column and attributes of the fish assemblages. We captured 1,167 individuals of fish belonging to 24 species. Oxygen was significantly higher in lower levels of macrophyte density and similar patterns were found for fish abundance and species richness. These results indicate that, in general, small sized-fish prefer less dense macrophyte stands. In addition, both depth and oxygen were significantly higher at the closest distance from open water, where the composition of fish species was also distinct from those found in other distances. In accordance with changes in species composition, different fish species showed divergent distribution along distances from the open water. Together these results demonstrate that oxygen content influences fish species composition, and indicate that fish species are able to use less suitable microhabitats most likely because of morphological, physiological and behavioral adaptations.

Aquatic macrophytes colonize a variety of environments, and they play important roles in ecosyste... more Aquatic macrophytes colonize a variety of environments,
and they play important roles in ecosystem
function and in community structure. One key challenge
for aquatic ecologists is to investigate the environmental
factors that drive the richness and distribution of these
plants. In this study, we assessed the importance of selected
morphometric variables and of the canopy openness of the
riparian vegetation to explain macrophyte species richness
and composition. We sampled macrophytes along gradients
of depth, littoral slope, distance from the connection with
the river, and canopy openness in floodplain lakes connected
with the Upper Parana´ River. We used quadrats to
survey a total of 40 sites in 11 lakes. We recorded 31
macrophyte species and found that macrophyte richness
was best and positively correlated with canopy openness.
This correlation suggests that canopy openness plays an
important role as an environmental filter, regulating the
amount of light availability for macrophytes. Macrophyte
species composition was best correlated with depth, indicating
that zonation of macrophyte species also occurs in
these shallow lakes. These findings emphasize the importance
of morphometric variables and canopy openness for
structuring macrophyte assemblages. In addition, our results
suggest that canopy openness and depth may be
considered in management strategies aiming to recover
macrophyte diversity and the processes mediated by
aquatic macrophytes in small and shallow floodplain lakes.

Ilha Grande National Park is an important conservation unit localized in the Southern part of the... more Ilha Grande National Park is an important conservation unit localized in the Southern part of the upper Paraná river floodplain (Brazil) that includes diverse aquatic environments. Oligochaeta (Annelida) is a large group of invert ebrates, with several small specimens inhabiting almost every possible niche at most freshwater ecosystem. The goal of the present study was to examine the spatial variation of Oligochaeta community in five floodplain lakes from the Ilha Grande National Park and relate the distribution with abiotic variables. Samples were taken at five sampling stations using a modified Petersen grab. Thirteen species of Oligochaeta belonging to two families Naididae and Tubificidae were recorded. Different patterns of richness and abiotic factors were identified among the lakes located in the island and at the margin of Paraná river. The different patterns of granulometric texture affected directly the distribution of the Oligochaeta assemblage of theses en vironments. The results of this study permit to infer that the Oligochaeta assemblage, in preserved areas, pr esent a higher richness in relation to long term studies with more frequent samplings. We concluded th at Ilha Grande National Park contributes for the preservation of benthic invertebrates.

Macrophytes increase structural complexity in aquatic ecosystems and their emergent structures pr... more Macrophytes increase structural complexity in aquatic ecosystems and their emergent structures provide habitats for spiders. We sampled spiders in three species of macrophytes (Eichhornia azurea, Eichhornia crassipes and Limnobium laevigatum) and measured five traits indicative of structural complexity: horizontal structure, vertical structure, plant height, macrophyte richness and macrophyte biomass. We tested the hypothesis that spider density and diversity increase and guild composition changes along a gradient of structural complexity provided by macrophytes. Vertical and horizontal structure and macrophyte richness covaried with the attributes of spider assemblages. However, vertical structure was an important habitat-complexity trait because it covaried with all spider attributes investigated, positively affecting density and taxa richness and changing guild composition. Our findings suggest that the increase in macrophyte structural complexity, primarily through vertical structure, provides additional habitat and microhabitat variability. These forms of variability may increase the availability of prey and shelter and even reduce intraguild predation between spiders, thereby potentially increasing density and taxa richness. Moreover, an increase in vertical complexity provides available structures for web attachment, favoring web-building spiders and consequently affecting guild composition. Thus, habitat structure plays an important role in structuring spider assemblages and specific traits may mediate changes in particular attributes of spider assemblages.

Habitat complexity has long been known to inﬂuence animal community structure by increasing the n... more Habitat complexity has long been known to inﬂuence animal community structure by increasing the number of available habitats. Fifty years have passed since MacArthur brothers published the sem-inal paper ‘‘On bird species diversity’’, which revolutionized studies of habitat structure. This paper ﬁrst evidenced and quantiﬁed the relationship between species diversity (birds) and habitat structural com-plexity (the number of stratiﬁed layers of landscape vegetation). In this article, we aim to pay homage to R. H. MacArthur’s contribution and to brieﬂy analyze the citation history and inﬂuence of ‘‘On bird species diversity’’, focusing primarily on aquatic studies. We searched for all papers that cited ‘‘On bird species diversity’’ on Thomson Reuters (ISI—Web of Knowledge) and analyzed them for temporal citation trends. In addition, considering only aquatic papers, we explored whether and how habitat complexity was measured, as well as the ecological organization level, attributes of organisms, taxonomic groups and study design (observational or experimental). ‘‘On bird species diversity’’ citations increased over time, but this paper was less cited by limnologists compared to terrestrial and marine scientists. The majority of investigations in aquatic ecosystems quantiﬁed habitat complexity, but few used mathematical modeling. The high number of citations, which continues to increase, shows the great inﬂuence of ‘‘On bird species diversity’’ on ecological studies and typiﬁes it as a classic in the ecological literature. However, the low citation frequency found in papers devoted to freshwater ecosystems indicates that limnologists in general neglect this original contribution in studies of habitat complexity.

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.

Aquatic macrophytes play an important role in structuring communities in aquatic environments. Th... more Aquatic macrophytes play an important role in structuring communities in aquatic environments. These plants provide physical structure, increase habitat complexity and heterogeneity and affect various organisms like invertebrates, fishes and waterbirds. The complexity provided by macrophytes has been exhaustively studied in aquatic environments. However, macrophyte complexity has rarely been measured in a standardized fashion, making comparisons among different studies and the establishment of general conclusions difficult. To address this issue, this review is focused on questions related to the habitat structural complexity provided by these plants, exploring: i) how complexity has been viewed by ecologists, with an emphasis on macrophyte studies; ii) the pros and cons of several methods used to quantify plant complexity; iii) the consequences of habitat structuring by macrophytes on invertebrates and fish and possible causes, mediated by habitat complexity, that lead to changes in these animal assemblages; iv) potential impacts of non-native macrophyte species on habitat complexity and v) the importance of complexity provided by macrophytes to management strategies for maintaining aquatic biodiversity. We examined literature produced in both temperate and tropical regions, but prioritized the latter. We found a great variety of habitat complexity measurements that are applied to aquatic macrophytes to understand their influence on attached animal assemblages. A lack of standardization (considering the wide range of techniques and scales of resolution used) limits comparisons between different studies exploring this subject, in which biological samples and physical substrates were used to explore these relationships. Macrophytes affect animal assemblages and promote biodiversity through a chain of mechanisms, related to habitat complexity, that involve the availability of shelter and feeding sites. Invasive macrophyte species may modify habitat structure and thus influence associated organisms. In this sense, they are suitable as the main focus of management strategies aimed at biodiversity restoration and conservation.

Natureza & Conservação, 2014