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Estudos que avaliam a importância da variacao intraespecifica na estrutura e funcionamento de comunidades de peixes de riachos ainda sao escassos. Entretanto, mensurar as caracteristicas ecologicas no nivel individual e de extrema importância, pois a resposta das especies frente as variacoes ambientais ocorre no nivel do individuo. Em riachos, onde as variacoes ambientais sao constantes, essa abordagem torna-se ainda mais necessaria. A variacao intraespecifica em peixes de riachos pode ser mensurada a partir de diferentes caracteristicas ecologicas, por exemplo, morfologia, dieta, historia de vida e uso do habitat, sendo que essas caracteristicas podem variar entre populacoes ou entre individuos da mesma populacao. O principal objetivo desse artigo foi apresentar metodologias e estudos que abordaram a variacao intraespecifica na ecologia trofica de peixes de riachos. Os estudos que relacionam o papel da variacao intraespecifica com a estrutura de populacoes e/ou comunidades foram selecionados, e suas principais implicacoes ecologicas, discutidas. As ferramentas de analise utilizadas para mensurar essa escala de variacao sao muitas, entre elas, os indices funcionais ( e.g. especializacao e originalidade intraespecifica), alem de analises multivariadas. Os resultados gerados a partir dessas analises individuais sao promissores e possuem grande potencial para explicar o funcionamento das populacoes e comunidades de peixes de riacho. INTRASPECIFIC VARIATION IN STREAM FISH WITH EMPHASIS ON TROPHIC ECOLOGY: Assessing intraspecific variability in community structure and functioning are still scarce for stream-dwelling fish. However, measuring ecological traits for individuals is important since species’ response for environmental conditions occurs at the individual level, especially in streams which suffers constantly physical disturbances. Intraspecific variability can be measured for several ecological traits, such as morphology, diet, life-history, and habitat use that varies between populations or within populations. Here, we present some methods and studies that evaluated intraspecific trophic variability in stream-dwelling fish. Results revealing the role of individual variation in structure of biological populations and/or assemblages were selected, and principal issues were discussed. There are a lot of statistical tools that can test individual variation including functional indexes and multivariate analyzes. Results generated from such individual analyzes have high potential to explain the functioning of stream fish populations and communities.

The effects of invaders on native species are usually tested using species mean trait values over long time scales. However, considering individual variation over short timescales can help us better understand the interaction between invaders and native species. We compared trophic traits of the non-native guppy (Poecilia reticulata) and the native Brazilian poeciliid Phalloceros harpagos using experiments simulating the early stages of an invasive process. We used short-term mesocosms to simulate an early invasion scenario, where the two species were placed together, and a pre-invasion scenario, where species were kept separated, and analyzed interspecific and intraspecific trophic variability. We also compared the foraging efficiency of species in laboratory experiments. We found no differences on the mean diet of both species between pre and early invasion treatments. At the individual level, in the early invasion scenario, individuals of both species reduced their trophic niche as a probable effect of the presence of the heterospecific. Phalloceros harpagos had higher consumption rates than guppies indicating greater efficiency in feeding on invertebrates. Our results suggest that non-native species were not intrinsically better consumers of high-quality resources. Instead, intraspecific variation might be playing an overlooked role in shaping interactions between species during the early stages of invasion.

Alien species often flourish and become invasive in urban ecosystems. How and why invaders succeed in urban systems is an important, yet poorly understood, question. We investigate whether the success of urban invaders is related to changes in species traits that enhance invasive potential. We also explore whether a trophic mechanism helps explain the success of invaders in urban systems. We use the guppy Poecilia reticulata, a globally distributed alien species that has invaded both urban and non‐urban systems, as our model.We first characterize the effect of urbanization on streams where guppies are present. We measure guppy invasion success using their population density and size‐frequency. Then we assess how traits that are related to the potential of guppies to invade (life history and condition) respond to urbanization. Next, we explore how urbanization affects the availability of food for guppies and their diets. We also test if the presence of other fish species grants biological resistance to invasion by dampening guppy invasive potential.We find that urban streams have high concentrations of ammonium and faecal coliforms, indicating contamination from sewage. On average, guppy populations from urban streams have 26× higher density and larger body sizes than non‐urban populations. Urban guppies are in better condition and have on average five more offspring than non‐urban guppies. Urbanization increases the availability and consumption of highly nutritious food (chironomid larvae) by guppies. We find a positive relationship between the consumption of chironomids and both fecundity and condition. The presence of other fish species in urban streams often has a negative but small effect on guppy traits and density.Our data suggest a relaxation of trade‐offs that shape life‐history traits which is related to increased food resources in urban streams. These indicate that urbanization enhances the invasive potential of guppies through a trophic mechanism that simultaneously increases reproduction and somatic investment. Such mechanism is likely widespread because chironomids are often highly abundant in urban systems. Thus, not only guppies but also other invasive species can take advantage of such a resource to invest in traits that enhance invasion success., This paper looks at how urbanization enhances the success of invaders by changing species traits. The authors find that urbanization provides high food quality and quantity, which allows invasive guppies to increase body size and condition, number of offspring and population density. This suggests that urbanization promotes a highly invasive phenotype.

We aimed to evaluate the relationship between form and function of two Loricariidae species (Hypostomus punctatus and Parotocinclus maculicauda) from a Neotropical coastal stream. We performed morphological-dietary analysis and discussed their coexistence strategies, as well. We hypothesized that both species use similar food resources according to their morphology but differences in habitat use facilitate their coexistence. In order to test this hypothesis, morphology, diet and habitat use were analyzed for both species. Trophic variance and the Pianka Niche Overlap index were calculated to explore the differences in trophic niche. Correlations between species abundance and water flow were applied to test habitat use. Principal Component Analysis and one Permutational Multivariate Analysis of Variance were applied to test differences between morphology and diet of both species. Morphological-dietary relationships were tested with Mantel test correlations. Total abundance of H. punctatus was higher in the stream channel with higher water flow. The dominant food items were sediment and organic matter for both species, and high trophic niche overlap was revealed. Additionally, morphology did not explain feeding habits for both species. Morphological characteristics were significantly different, especially for intestine length, relative area of the dorsal fin, ventral flattening and mouth attributes. The study site was rich in sand sediment, mud, and clay that are not considered good substrates to the establishment and growing of periphyton, which is an important trophic resource to Loricariidae species. Here, low consumption of periphyton can provide a possible explanation for the feeding similarity and the weak morphological-dietary relationships for both species. Thus, the environmental conditions can be more important for diet composition when compared to the similar and specialized morphology of loricariids.

The Mato Grosso is a typical Atlantic Forest stream located on the East coast of Brazil, approximately 70km from Rio de Janeiro city. From its source at about 800m a.s.l, the stream drains a 30km² area of the Northwestern part of the municipality of Saquarema, state of Rio de Janeiro and flows into the Saquarema Lagoon system. We hypothesized that fish species occupy distinct mesohabitats, with the prediction that their occurrences and densities differ among the microhabitats of riffles, runs and pools. A 250m-long stretch of the stream located in its uppermost part was selected for this study, where it becomes second-order. Mesohabitat description and their fish characterization were undertaken. Fish sampling was conducted by electroshocking and after their identification and counting, they were returned to the stream. For mesohabitat characterization, a Discriminant Function Analysis (DA) was applied. The total number of samples was estimated by the Zippin method and the recorded densities were used as an Indicator Species Analysis (ISA), followed by a Monte Carlo test for 1 000 permutations. The DA significantly separated the three predetermined mesohabitats (pool, riffle and run) (WL=0.13, F=187.70, p=0.001). We found five species of fishes, belonging to four families and three orders. The fishes Rhamdia quelen, Phalloceros harpagos, Pimelodella lateristriga and Astyanax taeniatus are indicators of the pool environment in the Mato Grosso stream, whereas Characidium cf. vidali is an indicator of the riffle environment. The Monte Carlo test detected non-random mesohabitat use only for P. lateristriga and A. taeniatus in the pools and for Characidium cf. vidali in the riffles. We concluded that the Mato Grosso stream contains three well-defined mesohabitats, with indicator species present in two of these mesohabitats. Rev. Biol. Trop. 58 (4): 1479-1487. Epub 2010 December 01.El estudio se realizó en el Río Mato Grosso (22º55‘ S-42º35‘ W), donde se encontraron cinco especies de peces, pertenecientes a cuatro familias y tres órdenes. Teniendo en cuenta la distancia filogenética y la evidente diferencia morfológica externa entre ellos, nuestra hipótesis es que ellos ocupan distintos mesohabitats y que las ocurrencias y densidades difieren entre mesohabitats, previamente definidos como corriente, rápido y remanso. La colección de peces fue realizada por pesca eléctrica, los peces fueron identificados, contados y devueltos al arroyo. Para la caracterización de mesohabitats se aplicó un análisis de función discriminante (AD). El número total de ejemplares fue calculado por el método de Zippin y las densidades fueron utilizadas para un análisis de especies indicadoras (AIE), seguido de la prueba MonteCarlo para 1 000 permutaciones. Los tres mesohabitats fueron separados de manera significativa por AD (WL=0.13, F=187.70, p=0.00), siendo las especies Phalloceros harpagos, Pimelodella lateristriga, Rhamdia quelen y Astyanax taeniatus indicativas del ambiente de remanso, mientras que Characidium cf. Vidali del ambiente rápido. Podemos concluir que este arroyo presenta tres mesohabitats bien definidos con la presencia de especies indicadoras en estos dos mesohabitats.

Deploying mosquito predators such as the guppy ( Poecilia reticulata ) into bodies of water where mosquitoes breed is a common strategy for limiting the spread of disease-carrying mosquitoes. Here, we draw on studies from epidemiology, conservation, ecology and evolution to show that the evidence for the effectiveness of guppies in controlling mosquitoes is weak, that the chances of accidental guppy introduction into local ecosystems are large, and that guppies can easily establish populations and damage these aquatic ecosystems. We highlight several knowledge and implementation gaps, and urge that this approach is either abandoned in favour of more effective strategies or that it is used much more rigorously. Controlling mosquitoes does not need to come at the expense of freshwater biodiversity.

In this work we aimed to characterise the diet of Astyanax taeniatus (Jenyns 1842) (Characiformes, Characidae) along the Mato Grosso stream and we hypothesised that the diet of this species would vary according to spatial, seasonal and ontogenetic differences. Specimens were collected every second month at three sites with different physical attributes. The feeding habits of 651 specimens were analysed using the Alimentary Index (IAi). Analysis of the diet showed an effect of spatial, temporal and ontogenetic factors. Vegetal allochthonous items were more important in the diet of Astyanax taeniatus in upstream sites while animal autochthonous items were more important downstream. Ontogenetic differences in the diet were significant only in upstream sites, where adults consumed a greater amount of vegetal matter than juveniles. These results reinforce the idea that Astyanax species are opportunistic and show trophic plasticity. Neste trabalho, objetivou-se caracterizar a dieta de Astyanax taeniatus (Jenyns 1842) (Characiformes, Characidae) ao longo do Rio Mato Grosso, com a hipótese de que a espécie apresente variações espaciais, sazonais e ontogenéticas. Os exemplares foram coletados bimestralmente em três localidades, que diferiram pelas variáveis físicas. As preferências alimentares foram analisadas a partir de 651 exemplares, utilizando-se o Índice Alimentar (IAi). Foram avaliadas diferenças espaciais, sazonais e ontogenéticas a partir dos dados de dieta. Os itens de origem vegetal e alóctone foram mais importantes na dieta da espécie para as localidades com maior altitude, enquanto os itens animais e autóctones, na localidade baixa. Na dieta de jovens e adultos, houve diferença significativa na contribuição de itens de origem vegetal e animal somente na localidade mais alta, onde os adultos consumiram maior quantidade de matéria vegetal. Os resultados reforçam a ideia de que as espécies de Astyanax possuem hábito alimentar onívoro e oportunista, evidenciando sua alta plasticidade alimentar ao longo do riacho.

High mortality rates have been observed in Teleost during early developmental stages, as well as great variations in reproductive tactics, which are related to adaptations towards environmental conditions and ecological niches for which different species have a specific response. The objective of this study was to describe reproductive tactics related to the survival of Cichlasoma orientale offspring, including aspects of body size, parental care, fecundity, oocyte size and spawning patterns. Samples were performed monthly from August 2011 to July 2013, in lentic and lotic environments at Curu river basin, Brazilian Northeastern semiarid region. Individual behavior (n=113) was observed underwater for over 50 hours by ad libitum sampling and focal-animal sampling. Collected individuals (males n=185, females n=95) were evaluated regarding the standard length, batch fecundity, oocyte size and spawning pattern. In females with mature ovaries, oocyte groups at different developmental stages were observed, these cells were counted and measured, and fecundity was estimated by the gravimetric method. Our results showed that the species displayed biparental care behavior and, on average, males were larger than females. Based on 46 ovaries, the average batch fecundity was 2 052±849 (range: 254-3 389). Standard length and batch fecundity were positively correlated, but no correlation was found between oocyte size and standard length. The maximum diameter observed in the most developed oocytes was 1.8mm. The observed distribution of oocyte size classes indicated synchronous oocyte development in three groups: previtellogenic, vitellogenic and mature, showing that C. orientale is a multiple spawner. Differences in the amount of oocytes among the three groups were observed, with the most developed group showing the smallest number of oocytes. The combination of low fecundity and large egg size is characteristic of demersal spawners due to a greater environmental stability. Multiple spawning increases chances of survival mainly because of increased fecundity per reproductive season, and the reduced competition among the offspring. We concluded that C. orientale makes a heavy investment in larval survival in detriment of the offspring number. Survival is favored by the large size of oocytes, large yolk reserve, biparental care and multiple spawning pattern.

The habitat use of a stream-dwelling Astyanax taeniatus from the State of Rio de Janeiro was investigated. We performed 12 h of underwater observation in a 200 m long stretch in the upper Roncador stream and quantified the following microhabitat descriptors: (i) water velocity, (ii) distance from the stream bank, (iii) substratum, and (iv) water column depth. Microhabitat selectivity was analyzed by comparing the microhabitat used by fish and the microhabitat available in the study site as well as by applying the Ivlev Electivity Index to the microhabitat use data. Differences in the use and availability of the various microhabitats revealed non-stochastic patterns of spatial occupation by A. taeniatus, which was selective for two of the four analyzed microhabitats. Our findings indicated that A. taeniatusis associated with habitats that have higher depths, low water velocity, and sand and bedrock substratum. O uso do micro-habitat por Astyanax taeniatus de riacho do estado do Rio de Janeiro foi investigado. Realizamos 12 h de observações subaquáticas em um trecho de 200 m do alto rio Roncador e quantificamos os seguintes descritores do micro-habitat: (i) velocidade da água, (ii) distância da margem, (iii) substrato, e (iv) profundidade da coluna d'água. A seletividade do micro-habitat foi analisada pela comparação do micro-habitat usado pelos peixes e o micro-habitat disponível na área de estudo, bem como pelo Índice de Eletividade de Ivlev aplicado aos dados de uso do micro-habitat. As diferenças no uso e disponibilidade dos diferentes descritores do micro-habitat revelaram um padrão não aleatório para a ocupação especial por A. taeniatus que foi seletivo para dois dentre quatro descritores analisados. Nossos registros indicaram que A. taeniatusestá associado à habitats com maior profundidade, baixa velocidade da água e substrato de areia e rocha.

In the present study we aimed to compare the feeding ecology of Hypostomus punctatus from a coastal stream from Southeast Brazil with data previously published for the same study site before environmental changes. Feeding preferences were assessed through a sample of 138 specimens (67 from the dry and 71 from the rainy season) using the Index of Alimentary Importance (IAi). We registered five different food items (detritus, plant fragments, Diatoms, Chloroficeae and Cianobacteries) composing the species diet. Detritus was the most abundant one both during the rainy and dry seasons (IAirainny = 90.34 and IAidry = 96.30). No significant differences were registered for the volume of food items consumed during the rainy and dry seasons. The Frequency of Occurrence analysis showed that four (detritus, plant fragments, Diatoms and Chloroficeae) among the five all other consumed ones, were always frequent. Comparing our own results with those available for the study site, we suggest that the feeding habit of H. punctatus has changed according to environmental changes and that the species diet is strongly dependent upon environmental conditions.