Appear of many studies published in tropical regions showing the effect on forest fragmentation and landscape isolation in biotic communities most studies have been made in continental regions. The impact of fragmentation and isolation of landscape in hydroelectric artificial reservoir are still poorly studies in the Amazonian. This study was done in island forest remain fragments created by the construction of the Tucurui Hydroelectric dam in the Para State, Brazil. The objectives of the study is to compare the islands on both sides of the reservoir in relation to the total size, total core area size, plot shape and degree of isolation to demonstrated the role of island to protected the local biota in landscape level and assess the species richness, abundance and species composition of the communities of lizard in the islands in local scale. At landscape level were chosen 199 islands in both margin of reservoir using satellite image of 2005. The total size of island varied from 3 to 1,768 hectares, being that 40% of island has less than 10 hectares in size. The islands have a significant loss of size, varying from 22% to 100% in relation to edge effects. There is no significant difference of the total size, total core area size and total edge of islands in relation to reservoir margins. However, the islands situated in the left margin of reservoir have high degree of isolation in compare to island from right margin. Most of the island analyzed in the Tucurui reservoir have small sizes, high loss of total area due to edge effects and irregular plot shape, all contributing. At local scale the lizard community was sampled in five field expedition carried out from January to July of 2005, using two methods of collect, transects and traps of interception and fall. We selected 12 islands based on total size, degree of isolation and position in relation to reservoir margin. We recorded 837 individuals of lizard distributed in 16 species. The most abundant species were Gonatodes humeralis and Coleodactylus amazonicus (Gekkonidae). The curve of total number of species in relation to field expedition reached the asymptote, showing that the five expeditions were sufficient to determine local species richness in the sampled island, corresponding to 84% of the total number of species determined by Jackknife 1 species richness estimator. There is significant difference in the species richness in relation to field expeditions, being highest species richness obtained from the third field expedition carried out from April to May of 2005. There is no significant difference in the species richness and number of individuals in relation to reservoir margins. There is significant and positive difference between the species richness in relation to size of island. There is no significant difference in the abundance of lizards in relation to size of island. There is significant difference in the species richness of lizards in relation to degrees of isolation of island, being the isolation lower in the more remote islands. However, the abundance of lizards in relation to degree of isolation of islands was not significant. There is no significant difference in the species richness in relation to open canopy and volume of litter. There is significant and positive difference between the species richness in relation to density of trunk falls and trees lives. There is no difference in the abundance of lizards in relation to forest structure parameters analyzed in the study. Finally there is no difference in the species composition of lizards in relation to reservoir margins, indicating that the Tocantins River in the sampled area analyzed in the study is not one important biogeography barrier to this group.
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