Roger Paulo Mormul

Removing the abyss between conservation science and policy decisions in Brazil

The executive and legislative branches of Brazilian government have either proposed or taken a variety of initiatives that threaten biodiversity and ecosystems. Opposition by the scientific community has largely been ignored by decision-makers. In this short essay, we present recent examples of harmful policies that have great potential to erode biodiversity, and we suggest ways to communicate scientific knowledge to decision- makers. If the current gap between conservation science and policies is not filled, the country will threaten the maintenance of its natural capital and, consequently, the sustainability of essential societal activities in the long term.

Epiphyton or Macrophyte: Which Primary Producer Attracts the Snail Hebetancylus moricandi?

Abstract: Relationships between snails, epiphyton, and macrophytes are widely studied because epiphytes decrease light for macrophytes, and snails may benefit the latter when they consume epiphytes. Thus, organic compounds released by macrophytes that attract snails could be an evolutionarily advantageous mechanism. This hypothesis was tested with three species of submerged macrophytes (natives: Egeria najas and Cabomba furcata; exotic: Hydrilla verticillata), which were maintained in microcosms in the presence of ancylid snails. However, the hypothesis of limpet attraction by macrophytes was rejected. Instead, epiphyton attached to E. najas attracted more snails than that attached to the other species. This attraction could be explained by chemical signals (organic compounds), released by certain species of algae that are detected by snails.

The “Tilapia Law” encouraging non-native fish threatens Amazonian River basins

Freshwater ecosystems in Brazil, arguably the most diverse on the planet, have been disturbed by several threats in the past years, particularly competition for water and subsequent water abstraction, urbanization, severe drought, dam construction/water diversion, pollution from different sources, commercial exploitation, and the introduction of non-native species (Agostinho et al. 2005; Vitule et al. 2015; Lima et al. 2015; Winemiller et al. 2016). A worrying example is the federal law 5989/2009 that intends to naturalize non-native fish species by decree in Brazil, some of which have a high invasion potential, such as the carps Aristichthys nobilis, Ctenopharyngodon idella, Cyprinus carpio, Hypophthalmichthys molitrix and tilapias Oreochromis spp. (Lima et al. 2012; Vitule

Propagule pressure, invasibility of freshwater ecosystems by macrophytes and their ecological impacts: a review of tropical freshwater ecosystems

In this review, we aim to draw parallels between the principal concepts of invasion biology, developed mainly for terrestrial plants in temperate regions, with findings for macrophytes recorded in tropical inland waters. In these ecosystems, the most important abiotic and biotic filters influencing invasion success are related to water and sediment conditions, light, disturbance, hydrology and the diversity and density of native species. The main impacts are related to direct and indirect changes in the populations and communities of native macrophytes and other associated organisms. Non-native ecosystem engineer species of macrophytes can affect ecosystems directly, and after affecting ecosystems, their effects can extend to populations and communities. High plant growth rates in the tropics could lead to rapid invasion and larger impacts compared to temperate ecosystems. Although we found many parallels between ecosystems regarding the general concepts of invasion, areas that should receive further investigation in the tropics include (i) the synergistic interaction of multiple invasive species, (ii) the effects of regime shift on invasion success and vice versa and (iii) how climate change will affect the dynamics of macrophyte invasion in tropical ecosystems.

Macrophyte Structural Complexity Influences Spider Assemblage Attributes in Wetlands

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.

Non-additive effects of macrophyte cover and turbidity on predator–prey interactions involving an invertivorous fish and different prey types

Habitat complexity, turbidity and prey type availability affect trophic dynamics, and an improved understanding of how these three factors work together could facilitate interpretations of trophic dynamics in environments with regime shifts. We conducted an experiment to cross these three factors, hypothesising that increasing both turbidity and macrophyte cover reduce consumption of Chironomids more than they reduce consumption of Cypridids. Our results did not support our hypothesis, suggesting that the effect of macrophyte cover on predation depends on turbidity. However, the magnitude of this combined effect is the same as that of turbidity alone. Moreover, turbidity affected predation on both prey types similarly. In addition, the effect of macrophyte cover on predation also depended on prey type. We argue that visual and physical refuges may be as effective as shelter, but macrophyte cover may benefit smaller prey items. This may lead to higher predation rates by small-sized fish on invertebrates during periods of low turbidity devoid of macrophyte cover and to similar predation rates on invertebrates during periods of low turbidity and abundant macrophytes, high turbidity and scarce macrophytes or high turbidity and abundant macrophyte cover.

Structural complexity and turbidity do not interact to influence predation rate and prey selectivity by a small visually feeding fish

Structural complexity and turbidity decrease predation by respectively providing a physical and visual refuge for prey. It is still unclear how the covariance between these variables could drive predation and prey selectivity. We experimentally simulated scenarios that are temporally observed in floodplain rivers. In the experiments, we crossed different prey types, structural complexity and turbidity. We hypothesised that the negative relationship between structural complexity and predation would become stronger with a linear increase in the turbidity level and that an increase in structural complexity and in turbidity would change prey selectivity from a selective to a random pattern. Our results showed that the effects of structural complexity and turbidity on predation may not covary; a linear increase in turbidity did not significantly change the patterns of predation or prey selectivity. In contrast, structural complexity significantly reduced prey consumption according to prey size. We argue that areas with low macrophyte cover may provide an efficient refuge for smaller prey, whereas an efficient refuge for larger prey can be attained only in areas with high macrophyte cover. In highly complex habitats, specificity in prey consumption is precluded because both prey species can hide amid the interstices of the macrophytes, leading to random prey selectivity.

Swimming and hiding regardless of the habitat: prey fish do not choose between a native and a non-native macrophyte species as a refuge.

The ability to respond to a predation threat may be the key factor influencing prey survival. Thus, small-sized fish may adapt to use macrophyte patches as refugia in ecosystems where they face predators. We evaluated the habitat choices of a small fish species (Serrapinnus notomelas) to determine whether these fish prefer native versus recently introduced submerged macrophyte stands in the context of predator avoidance. Specifically, we applied three predator cue treatments: no cue, chemical cue from a hungry predator and presence of a satiated predator. First, we empirically tested the theoretical assumption that the prey fish use vegetated habitats and that the presence of an actual predator has a stronger effect on the choice of habitat than simply a chemical cue. Then we tested the hypothesis that prey do not choose a habitat according to macrophyte species and whether this pattern changed as a result of increasing predation risk. We found that the prey fish preferred vegetated habitats; however, they did not appear to distinguish native from invasive macrophytes. Our results support the hypothesis that the physical structure of macrophytes is more important in determining habitat choice than the evolutionary relationship between the fish and the native macrophyte species.

Association of body size and behavior of freshwater ostracods (Crustacea, Ostracoda) with aquatic macrophytes

In aquatic systems, macrophytes play an important role in habitat structuring and can be relevant for the establishment and/or mobility of the organisms and might thus influence species composition. This study evaluates the influence of the structural complexity of aquatic plants on the community composition of Ostracoda in the upper Paraná River floodplain. We tested the hypothesis that non-swimming and small-sized species have a higher association with more complex plants by a threshold indicator taxa analysis. Some small and non-swimming ostracod species had a significant affinity for macrophytes with higher complexity, especially Eichhornia crassipes. However, most species did not show an association with the structure of aquatic macrophytes, and there was only a slightly distinction among the communities of different plants. The results show that structural complexity is in some cases an important determining factor for the community composition of Ostracoda, but other factors may interact with and even override the effects of complexity. It can thus be concluded that the relation between habitat complexity and the Ostracoda community composition is complex and not always responds to general predictions.

Podostemum rutifolium subsp. rutifolium como estruturador da comunidade de algas perifíticas em um rio neotropical

As plantas da familia Podostemaceae possuem carater riacofilo, crescendo sobre substrato rochoso. O presente estudo foi desenvolvido no rio Parana com o objetivo de registrar Podostemum rutifolium Warm. subsp. rutifolium e analisar a composicao, a riqueza e a densidade da comunidade de algas perifiticas nesta macrofita. Para amostragem, foi utilizado um quadrado de borracha (25 cm2), mergulho em apneia e a remocao da planta aderida a rocha. Posteriormente foi realizada a remocao, fixacao, identificacao e contagem das algas perifiticas deste substrato. Foram identificadas 137 especies de algas perifiticas distribuidas em nove classes. O maior numero de taxons pertenceu a classe Bacillariophyceae, seguida por Cyanophyceae. Esse padrao ja foi encontrado para a maioria dos ambientes loticos da planicie de inundacao do rio Parana. Embora seja uma especie de habito incrustante, a arquitetura de P. rutifolium fornece microhabitats para muitas especies de algas. Portanto, sugere-se que essa macrofita seja uma especie chave na estruturacao da comunidade algal perifitica e sua remocao poderia acarretar no declinio na diversidade do perifiton, principalmente por ser a unica especie presente como substrato vegetal na area amostrada.