Assuntos

RESUMO

A better understanding of species coexistence and community dynamics may benefit from more insights on trait variability at the individual and species levels.Tadpole assemblages offer an excellent system to understand the relative influence of intraspecific and interspecific variability on community assembly, due to their high phenotypic plasticity, and the strong influence that environmental variables have on their spatial distribution and individual performance.Here, we quantified the intraspecific and interspecific components of tadpoles' trait variability in order to investigate their relative role in shaping tadpole communities.We selected eight functional traits related to microhabitat use, foraging strategies, and swimming ability. We measured these traits on 678 individuals from 22 species captured in 43 ponds in the Atlantic Forest. We used single- and multitrait analyses to decompose trait variability. To explore the action of external and internal filtering on community assembly, we used a variance decomposition approach that compares phenotypic variability at the individual, population, community and regional levels.On average, 33% of trait variability was due to within-species variation. This decomposition varied widely among traits. We found only a reduced effect of external filtering (low variation in the height of the ventral fin within ponds in comparison to the total variation), whereas the internal filtering was stronger than expected. Traits related to the use of different microhabitats through the water column were generally less variable than traits related to swimming ability to escape of predators, with tail traits being highly variable within species.Our study highlights the importance of incorporating both intraspecific and interspecific, trait differences and of focusing on a diversity of traits related to both stabilizing niche and fitness differences in order to better understand how trait variation relates to species coexistence.

RESUMO

One of the most important goals of biodiversity studies is to identify which characteristics of local habitats act as filters that determine the diversity of functional traits along environmental gradients. In this study, we investigated the relationship between the environmental variables of ponds and the functional trait diversity distribution of anuran tadpoles in an agricultural area in southeastern Brazil. Our results show that the functional trait diversity of frog tadpoles has a bell-curve-shaped relationship with the depths of ponds inserted in a pasture matrix. Because we are witnessing increasing human pressure on land use, simple acts (e.g. maintaining reproductive habitats with medium depth) can be the first steps towards preserving the diversity of Neotropical frog tadpole traits in agricultural landscapes.

RESUMO

One of the main pesticides used in the cultivation of sugarcane in São Paulo State, Brazil, is Regent(®)800WG, the main active compound of which is fipronil. Fipronil is a potent insecticide that eliminates pests, including insects resistant to pyrethroids, organophosphates (OP) and carbamates (CA). There is little known on the toxic effects of fipronil on non-target organisms, such as tadpoles of frogs. It is possible that this compound carries a high toxicity for these organisms, since the pesticide can be incorporated into aquatic environments during the rainy season, a time which coincides with the time of amphibian reproduction and the occurrence of tadpoles in the aquatic environment in this region. Thus, the pesticide could be contributing to the decline of amphibians in the northwest region of São Paulo state due to its wide use. This study aimed to test the influence of Regent(®)800WG on some biochemical systems of tadpoles (such as antioxidant defense systems) at different stages of development. The results of analysis from in vivo exposures demonstrated that only a few parameters in the groups exposed to fipronil responded to exposure to Regent(®)800WG, results which indicate that the pesticide instigates biochemical responses in tadpoles. Although catalase and glucose-6-phosphate dehydrogenase (G6PDH) were unchanged during the experiments, glutathione-S-transferase (GST) was inhibited in tadpoles, and the activity of glutathione reductase (GR) varied according to the exposure period and pesticide concentration. This data demonstrated the influence of the fipronil formulation on the metabolism of tadpoles, and showed that it can increase their susceptibility to environmental contaminants.

Assuntos

RESUMO

The structure of the fish communities of a pool and a rapid in the ribeirão Santa Bárbara is described. This stream of 5th order is a direct tributary of the rio Tietê in the system of the upper rio Paraná. Thirty three species, from nine families and three orders, were referred in the two mesohabitats: the pool with 31 species, and the rapid with 18. Orders Characiformes, Siluriformes, and Perciformes presented the greatest number of species in the two mesohabitats. The families Characidae and Loricariidae were the most specious, followed by Cichlidae in the pool, and by Parodontidae in the rapid. Most species were accidental, 17 in the pool, and 10 in the rapid, and only six were constant in the two mesohabitats. The greatest diversity and evenness occurred in the pool. The seasonal variation for both assemblages was high, with the pool having a high turnover of species that could be due to the proximity with main channel of the rio Tietê.

A estrutura das comunidades de peixes de um poço e uma corredeira do ribeirão Santa Bárbara é descrita. Esse é um ribeirão de quinta ordem, afluente direto do rio Tietê no sistema do Alto rio Paraná. Trinta e três espécies, de nove famílias e três ordens, foram capturadas nos dois meso-hábitats: 31 no poço e 18 na corredeira. Characiformes, Siluriformes e Perciformes apresentaram o maior número de espécies nos dois meso-hábitats. As famílias Characidae e Loricariidae foram as mais ricas em espécies, seguidas por Cichlidae, no poço, e por Parodontidae, na corredeira. A maioria das espécies foi acidental, 17 no poço e dez na corredeira; somente seis espécies foram constantes nos dois meso-hábitats. As maiores diversidade e uniformidade ocorreram no poço. A variação sazonal no poço e na corredeira foi alta, com o poço apresentando uma grande substituição de espécies, que pode ser devida à proximidade com o canal principal do rio Tietê.

RESUMO

The structure of the fish communities of a pool and a rapid in the ribeirão Santa Bárbara is described. This stream of 5th order is a direct tributary of the rio Tietê in the system of the upper rio Paraná. Thirty three species, from nine families and three orders, were referred in the two mesohabitats: the pool with 31 species, and the rapid with 18. Orders Characiformes, Siluriformes, and Perciformes presented the greatest number of species in the two mesohabitats. The families Characidae and Loricariidae were the most specious, followed by Cichlidae in the pool, and by Parodontidae in the rapid. Most species were accidental, 17 in the pool, and 10 in the rapid, and only six were constant in the two mesohabitats. The greatest diversity and evenness occurred in the pool. The seasonal variation for both assemblages was high, with the pool having a high turnover of species that could be due to the proximity with main channel of the rio Tietê.

A estrutura das comunidades de peixes de um poço e uma corredeira do ribeirão Santa Bárbara é descrita. Esse é um ribeirão de quinta ordem, afluente direto do rio Tietê no sistema do Alto rio Paraná. Trinta e três espécies, de nove famílias e três ordens, foram capturadas nos dois meso-hábitats: 31 no poço e 18 na corredeira. Characiformes, Siluriformes e Perciformes apresentaram o maior número de espécies nos dois meso-hábitats. As famílias Characidae e Loricariidae foram as mais ricas em espécies, seguidas por Cichlidae, no poço, e por Parodontidae, na corredeira. A maioria das espécies foi acidental, 17 no poço e dez na corredeira; somente seis espécies foram constantes nos dois meso-hábitats. As maiores diversidade e uniformidade ocorreram no poço. A variação sazonal no poço e na corredeira foi alta, com o poço apresentando uma grande substituição de espécies, que pode ser devida à proximidade com o canal principal do rio Tietê.