Spatial diversity patterns of birds in a vegetation mosaic of the Pantanal, Mato Grosso, Brazil

In this contribution we characterize the spatial diversity of bird populations in a heterogeneous landscape with respect to vegetation in the northern Pantanal region of Brazil. The method of additive partitioning of species diversity (γ = α + β) was used. Samples were collected in a grid with 30 sampling plots within a 25 km² area (5 x 5 km). A total of 163 bird species were found, comprising 114 resident species and 49 regional migrants. Most species were restricted spatially, with 58% found in a maximum of five sampling plots, while 15% were found in only one plot. The beta diversity comprised 77% of total diversity and was lower for residents than for regional migrants (66% and 88%, respectively). This suggests greater spatial heterogeneity in diversity patterns for regional migrants. Seasonal availability of resources caused by changing water levels as well as anthropogenic influences may also play a role in species diversity patterns by influencing species composition across sampling plots. High beta diversity and species-specific habitat occupancy suggest that conservation and management strategies should be implemented at a regional spatial scale and focus on the conservation of this environmental mosaic

Distribuição e alimentação de duas espécies simpátricas de piranhas Serrasalmus maculatus e Pygocentrus nattereri (Characidae, Serrasalminae) do rio Ibicuí, Rio Grande do Sul, Brasil Distribution and feeding of two sympatric species of piranhas Serrasalmus maculatus and Pygocentrus nattereri (Characidae, Serrasalminae) of the Ibicuí river, State of Rio Grande do Sul, Brazil

Duas espécies de piranhas ocorrem no rio Ibicuí, um dos principais afluentes do rio Uruguai. Com o objetivo de analisar a distribuição e a alimentação destas espécies, foram realizadas coletas de dezembro de 1999 a janeiro de 2002, utilizando-se diferentes artes de pesca em três pontos do rio, sendo que cada ponto foi amostrado em dois ambientes (lêntico e lótico). Foram capturados 203 indivíduos de Serrasalmus maculatus Kner, 1858 e 86 de Pygocentrus nattereri Kner, 1858, sendo que a maior captura de ambas as espécies ocorreu no ambiente lêntico e próximo ao rio Uruguai, onde P. nattereri parece estar mais concentrada. O número de exemplares capturados por horário não apresentou variações significativas em P. nattereri enquanto que S. maculatus apresentou a maior captura na revisão da meia-noite. Juvenis de S. maculatus (2-4 cm de comprimento padrão) consumiram preferencialmente nadadeiras e insetos. Nas demais classes de tamanho de ambas as espécies, restos de peixes foi o alimento predominante, havendo sobreposição alimentar intra e interespecífica nas maiores classes (8-16 cm e >16 cm de comprimento padrão). Não foram constatadas diferenças no índice de repleção entre os horários e os ambientes para as duas espécies.<br>Two species of piranhas occur in the Ibicuí River, one of the main tributaries of the Uruguay River in southern Brazil, Serrasalmus maculatus Kner, 1858 and Pygocentrus nattereri Kner, 1858. In order to analyze the distribution and feeding habits of these species we conducted collecting expeditions from December 1999 to January 2002, using a variety of fishing gears in three sites along the river, both in lentic and lotic habitats. A total of 203 individuals of S. maculatus and 86 of P. nattereri were caught, mostly in lentic habitats and closer to the Uruguay River, were P. nattereri seems to be more concentrated. The number of individuals captured at different times did not show variation in P. nattereri while the number of S. maculatus captured at mid-night was the highest. Young S. maculatus (2-4 cm standard length) fed mainly on fish fins and insects. Fish was the predominant item in remaining size classes for both species, with intra- and inter-specific overlap in larger classes (8-16 cm and >16 cm standard length). No differences in the repletion index between day time or habitats, were observed for the two species