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Skora F.,Federal University of Parana | Abilhoa V.,Grupo de Pesquisas em Ictiofauna | Padial A.A.,Federal University of Parana | Vitule J.R.S.,Federal University of Parana
Diversity and Distributions

Aim: We examined fish establishment trends in the aftermath of the connection of two Neotropical freshwater ecoregions. Darwin's conundrum was used to examine whether taxonomic and functional relatedness would explain establishment or whether the establishment of new populations was driven by ecological interactions (Darwin's naturalization hypothesis, DNH) or by shared environmental requirements (adaptation hypothesis, AH). Location: Paraná River, south-eastern South America. Methods: Taxonomic relatedness was investigated using a one-tailed Fisher exact test, considering all species and monophyletic groups. Functional traits were used to estimate niche dissimilarities among non-native species and across the entire set of native species, generating distributions that were fitted to exponential or logarithmic curves, based on a new conceptual model. Results: Of the 213 species from the Lower Paraná River that had the opportunity to reach the Upper Paraná River, 25% - 53 spp. - were successfully established. The ratios of unshared to shared genera for both successful and unsuccessful non-native species were not different, but 7% of type I error probability for Characiformes and 8% for all species, would favour DNH. Our results indicate that both DNH and AH could explain successes but that DNH was more likely to explain failures in establishment. Main conclusion: Darwin's naturalization hypothesis is more likely to explain the non-native establishment in invasion processes. Both the DNH and AH explain successful colonization, but DNH provided the best explanation for failed non-native establishments. Non-native species that were functionally similar to native species (i.e. with similar traits) were more likely to fail, suggesting that biotic resistance was directly linked to ecological similarity. Biotic resistance could be the most important mechanism for explaining establishment or failure of non-native species. The conceptual model proposed here can be used to predict which non-native species are least likely to establish, based on the functional traits of species in the native community. © 2015 John Wiley & Sons Ltd. Source

Vitule J.R.S.,Federal University of Parana | Skora F.,Grupo de Pesquisas em Ictiofauna | Skora F.,Federal University of Parana | Abilhoa V.,Grupo de Pesquisas em Ictiofauna
Diversity and Distributions

Aim We quantify biotic homogenization of fish fauna caused by the elimination of a natural barrier between two freshwater ecoregions. We also evaluated fish introductions by different mechanisms such as aquaculture, angling and the aquarium trade in the homogenization of fish assemblages. The relative importance of native extinctions in the homogenization process was assessed by simulating the exclusion of threatened species in the data set. Location Paraná River, south-eastern South America. Methods A fish species list of the Parana River Basin was organized in a subset of species distributions, according to pre- and post-introductions caused by the elimination of the natural barrier and by other mechanisms. Biotic homogenization was verified by the use of Jaccard's and Bray-Curtis's coefficients, Whittaker's beta diversity index, non-metric multidimensional scaling analysis (NMDS) and nonparametric tests. Results For all subsets of species distributions, we observed an increase in the number of non-native species in common related to the introductions. Between 40 and 52% of the species currently present in the Upper Paraná Basin dispersed upstream from the Lower Paraná after the construction of Itaipu Dam, including at least 1 class, 2 orders, 4 families and 16 genera of fish. Jaccard's coefficient between the Upper and Lower Parana River increased by 6-7.5% only considering the Itaipu Dam influence and 10.5% considering all mechanisms of fish introductions. More than 50% of the increase in similarity was caused by the elimination of the barrier. Our results indicated functional homogenization related to large-bodied Siluriformes (catfish). Main conclusions Itaipu Lake flooded a natural barrier and allowed hydrologic connectivity between the Upper and Lower Paraná River, and many fishes of the lower part of the river were able to colonize the upper stretches. The homogenization of the two assemblages between these adjacent aquatic regions was an unpredicted result of hydropower implementation. Introductions by dam can also shift longitudinal and latitudinal body size patterns (i.e. Bergmann's rule). © 2011 Blackwell Publishing Ltd. Source

Vitule J.R.S.,Federal University of Parana | da Silva F.F.G.,Federal University of Parana | Bornatowski H.,Grupo de Pesquisas em Ictiofauna | Bornatowski H.,Federal University of Parana | And 2 more authors.
Environmental Biology of Fishes

Feeding ecology of fish assemblage in a costal river of the Atlantic Rain Forest in Southern Brazil was investigated. Monthly samples using different fishing techniques were completed on a section of the river characterized as a freshwater environment, and an adjacent tide-influenced estuarine section. Species were grouped into three major Feeding Mode Functional Groups: Zoobenthivore, Omnivore and Detritivore. The river section with the greatest occurrence was the site where the most abundant species are likely to feed most intensively. Freshwater strangler species (Cyphocharax santacatarinae - detritivorous, Rhamdia quelen and Oligosarcus hepsetus - zoobenthivorous) presented higher stomach repletion in the freshwater environment while marine migrants (Genidens genidens and Etropus crossotus - zoobenthivorous) and estuarine residents (Bairdiella ronchus - zoobenthivorous) presented higher repletion in the tide-influenced estuarine stretch. Use of food resources was influenced by spatial and temporal variations linked to environmental characteristics such as salinity, habitat heterogeneity, life history evolution, feeding specialization and resource partitioning. Hypotheses concerning potential keystone species, ecosystem engineers or strong interactors were also discussed. © 2012 Springer Science+Business Media Dordrecht. Source

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