Metacommunity composition of web-spiders in a fragmented neotropical forest : relative importance of environmental and spatial effects

The distribution of beta diversity is shaped by factors linked to environmental and spatial control. The relative importance of both processes in structuring spider metacommunities has not yet been investigated in the Atlantic Forest. The variance explained by purely environmental, spatially structured environmental, and purely spatial components was compared for a metacommunity of web spiders. The study was carried out in 16 patches of Atlantic Forest in southern Brazil. Field work was done in one landscape mosaic representing a slight gradient of urbanization. Environmental variables encompassed plot- and patch-level measurements and a climatic matrix, while principal coordinates of neighbor matrices (PCNMs) acted as spatial variables. A forward selection procedure was carried out to select environmental and spatial variables influencing web-spider beta diversity. Variation partitioning was used to estimate the contribution of pure environmental and pure spatial effects and their shared influence on beta-diversity patterns, and to estimate the relative importance of selected environmental variables. Three environmental variables (bush density, land use in the surroundings of patches, and shape of patches) and two spatial variables were selected by forward selection procedures. Variation partitioning revealed that 15% of the variation of beta diversity was explained by a combination of environmental and PCNM variables. Most of this variation (12%) corresponded to pure environmental and spatially environmental structure. The data indicated that (1) spatial legacy was not important in explaining the web-spider beta diversity; (2) environmental predictors explained a significant portion of the variation in web-spider composition; (3) one-third of environmental variation was due to a spatial structure that jointly explains variation in species distributions. We were able to detect important factors related to matrix management influencing the web-spider beta-diversity patterns, which are probably linked to historical deforestation events

Estabilidade e persistência de uma comunidade de peixes em lagoa costeira neotropical

Studies approaching the temporal variation of fish community structure on coastal lagoons give us the opportunity to access its stability and persistence, besides of being important tools to monitor the quality of environment. However, few researches use a temporal approach to evaluate this kind of ecosystems. The present study aimed to compare the fish community structure of Caconde lagoon, north coast of RS, at two time periods (1992-1994 and 2009-2011). A Student’s t-test was used to compare the proportion of abundance and of biomass of each species between the two time periods. Additionally, we performed an ordination with the fish species compositions of the two periods. Five new species occurrences were registered for Caconde lagoon at the recent sample, three of which are allochthonous. Eight species found at the original sample were not found at the recent one. Results of t-test revealed significant differences on the abundances of four species as well as a temporal partition between the two temporal samples. Besides the presence of allochthonous species, we found differences in the stability of the community characterized by decreasing relative abundances of original dominant species. Notwithstanding the inability to clearly explain the causes of the observed changes, we infer they can be partly explained by the presence of allochthonous species as well as by land-use changes at lagoon surroundings.Estudos que avaliam comunidades de peixes em lagoas em intervalos distintos no tempo nos fornecem uma oportunidade para o exame de sua estabilidade e persistência, além de serem úteis como indicadores de qualidade ambiental. Porém são poucos os trabalhos feitos com o enfoque na avaliação temporal desses ecossistemas. Este trabalho objetivou comparar amostragens da ictiofauna da lagoa Caconde, litoral norte do RS, feitas em dois períodos distintos (1992-1994 e 2009-2011), visando avaliar possíveis mudanças na estrutura da comunidade de peixes deste sistema. Fez-se a comparação entre as amostragens do primeiro (1992-1994) e segundo (2009-2011) períodos, através de teste t, entre a abundância proporcional de espécies constantes, tanto em número de indivíduos quanto em biomassa. Além disso, foi feita uma análise de ordenação entre a composição de espécies da lagoa em cada período amostral. Registraram-se cinco novas ocorrências na lagoa Caconde, sendo que três delas foram de espécies alóctones. Oito espécies registradas no primeiro período não foram capturadas no segundo. O teste t realizado revelou diferenças significativas na abundância de quatro espécies, bem como uma partição temporal entre amostragens dos dois períodos. Além da presença de espécies alóctones, a maior diferença encontrada entre os dois períodos amostrais refere-se a alterações na estabilidade, através da mudança de espécies que, antes dominantes na comunidade, diminuíram suas abundâncias relativas. Apesar de não poder indicar claramente as causas das alterações registradas, é possível que estas mudanças sejam em decorrência da presença das espécies alóctones, além das mudanças do uso do solo do entorno da lagoa

Anthropogenic influences on the distribution of a threatened apex-predator around sustainable-use reserves following hydropower dam installation

Although previous studies demonstrate declines in many large bodied species following hydropower dam installation, others suggest that some species, including the giant otter (Pteronura brasiliensis) may return to newly created reservoir habitats. Yet, there is a lack of evidence to support such theories. Here, we analyzed the effects of a hydropower dam on giant otters using a before-after control-impact study design in the eastern Brazilian Amazon. We collected data 3 years before (2011–2012 and 2015) and after (2017–2019) dam construction, totaling 6,459 km of surveys along rivers with 43 direct sightings of giant otters. Contrary to expectations, our results revealed that giant otters did not remain nor did they return to the dam reservoir. Beyond the zone directly impacted by the dam giant otter occurrence and relative abundance declined next to sustainable-use reserves where the river was more intensely used by people. Our study showed that in the absence of active management sustainable-use reserves and low human density were not sufficient to maintain this apex-predator. Our findings suggest a need to proactively create and maintain areas with low levels of anthropogenic disturbance to enable sustainable coexistence between energy demands and biodiversity across Amazonia

Functional redundancy of non-volant small mammals increases in human-modified habitats

Aim: Humans are rapidly altering natural habitats across much of the globe. Here we compared 264 globally distributed communities in natural and human-modified habitats to detect changes in community richness and functional diversity with human influence. Location: Global. Taxon: Non-volant small mammals. Methods: We calculated differences in observed to potential species richness (ΔSR) and observed to potential functional diversity (ΔFD) to account for regional pool differences. Then we determined the prevalence of four distinct scenarios of richness and functional diversity differences between human-modified and natural habitats, and evaluated local and geographical variation in these differences. We obtained potential richness by calculating a probabilistic species pool and obtained potential functional diversity through the n-dimensional hypervolume based on pool composition. We tested for differences in average ΔSR and ΔFD between habitats, and determined the most common scenario of ΔSR and ΔFD in human-modified and natural habitats. Results: We found lower ΔSR in human-modified than natural habitats, but no difference in ΔFD. Low ΔSR and high ΔFD predominated in human-modified habitats, and high ΔSR and ΔFD in natural habitats. Low ΔSR and high ΔFD predominated in temperate forests, whereas high ΔSR and ΔFD in tropical forests and grasslands. Scenarios of low ΔSR and high ΔFD, and high ΔSR and low ΔFD, were most common in human-modified and natural habitats of temperate grasslands. Main conclusions: A larger richness in human-modified habitats does not result in larger functional diversity. Rather there seems to be an increase in functional redundancy because species which profit from human modification do not bring new functions into human-modified habitats. While greater richness is found in humanmodified habitats from temperate biomes, this is not the case in extremely biodiverse tropical biomes. Assuming a positive relationship between richness, functional traits and ecosystem function, greater richness in modified habitats may not yield greater function

Color polymorphism and variation in microhabitat selection: a defensive strategy in males of Boana pulchella (Anura: Hylidae)?

Anurans vary in body coloration and frequently exhibit color polymorphism, with selection by predation pressure favoring more cryptic animals. Spatial differentiation may also favor color polymorphism in some species, since cryptic morphotypes can use substrates that better match their coloration. Boana pulchella is a polymorphic species with green and brown morphotypes, but its polymorphism remains poorly understood. The aim of the present study was to determine the functionality of color polymorphism in B. pulchella as a defense strategy. Artificial green and brown clay models were placed in environments with green and brown background to determine if the two morphotypes of B. pulchella experience different frequencies of attacks. We expected that more conspicuous morphs are attacked more frequently. The attack rate, which suggests predation intent, on the models was 9.57%. The marks observed in the artificial models were left by both mammals and birds. The number of damaged models did not significantly differ between the different background environments. The results indicate that B. pulchella morphotypes are equally cryptic to predators in the studied environments. In conclusion, probably color polymorphism in B. pulchella is not operating as a defensive strategy, and other selective forces may be acting in the maintenance of color polymorphism in this species

Inventário Rápido da Fauna de Mamíferos do Morro Santana, Porto Alegre, RS

The variety of morph structural and vegetation formations is a very peculiar characteristic in the city of Porto Alegre. The highest hill of the city is the Morro Santana, which reaches 311m. Due to its relative conservation status, it represents a very important natural fragment amongst the urbanized area. A legally protected area is intended to be established in a 370ha area that belongs to the Universidade Federal do Rio Grande do Sul. In order to contribute to the conservation and management policies of natural resources essentially needed in any protected area, this study proposes to rapid survey about mammalian species occurring in the area. Traps and mist nets were used to capture small mammals. Sightings and tracks were found randomly, as well as interviews, completed the results. A total of 15 mammal species were registered. Rodents were the most numerous family in species richness, reaching the number of six. Interviews resulted in 17 species, seven of which were also registered with capture, sighting and track methods. The majority of mammals in the area is generalist and versatile in habitat use. Most of them seem to tolerate altered environments and seem to be adapted to the presence of people and urban areas. The species diversity found in Morro Santana suggests that the area still has a reasonable conservation status, despite the high amount of environmental impacts already presented.Em Porto Alegre, a variedade de formações morfoestruturais e vegetacionais é uma característica marcante. O Morro Santana é o ponto culminante da cidade, com 311 metros de altitude. Representa uma área importante para o município de Porto Alegre pelo seu relativo grau de conservação em meio à malha urbana, onde se pretende implementar uma unidade de conservação nos 370 ha pertencentes à Universidade Federal do Rio Grande do Sul. No intuito de contribuir com as políticas de conservação e manejo de recursos naturais essenciais em uma unidade de conservação, este trabalho objetivou realizar um inventário rápido das espécies de mamíferos ocorrentes no Morro Santana. Foram utilizadas armadilhas de arame para capturas de pequenos mamíferos terrestres e redes de neblina para quirópteros. Visualizações, vestígios encontrados ao acaso e entrevistas foram métodos utilizados para complementar as coletas. Foi registrada a ocorrência de 15 espécies compondo a mastofauna do Morro Santana. A ordem com maior número de espécies foi a dos roedores, que chegou a seis espécies registradas. Das entrevistas registrou-se 17 espécies, das quais sete delas foram registradas também por capturas, visualização e vestígios. A grande maioria dos mamíferos ocorrentes no local é de hábitos generalistas e usa variados tipos de hábitat. Muitas destas espécies parecem tolerar alterações antrópicas no ambiente assim como a se adaptar à presença de pessoas e zonas urbanizadas. A relativa riqueza de espécies encontradas sugere que o Morro Santana ainda se encontra em razoável estado de conservação, apesar do impacto ambiental já sofrido

Composição da dieta de Procyon cancrivorus (Mammalia, Carnivora) no Parque Estadual de Itapuã, RS, Brasil : dados preliminares

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