Ilhas florestais, redes de interação formiga-planta e a conservação de processos ecológicos

Abstract

Ant-plant mutualism is an important feature of the Amazon biodiversity. Its coevolutionary trajectories which generated tight compartmented networks are nowadays threatened by habitat alteration. The recent Brazilian demand for energy is leading to the construction of a series of hydroelectric which causes habitat loss and fragmentation. Our goal is to test how dam fragmentation affects the structure of ant-plant mutualistic networks, in particular species density and richness, connectance, modularity, and nestedness. We compared the networks of continuous forest with those from islands and lake edges as well as how networks change among islands varying in area, isolation, shape, and neighborhood. We developed the study in the Biological Reserve of Uatumã in Central Amazon, which includes the continuous forest around the 3147 km 2 of the Balbina dam reservoir and more than 3500 islands. Ant-plant communities were surveyed along 600 x 5 m plots in 20 islands, 5 lake edges, and 6 forests sites. Plant and ant richness and density was lower in islands and lake edge in comparison with forest, increased with island area and decreased with isolation. Density of all myrmecophyte species decreased from forest to lake edge and island. Unoccupied plants percentage was three times higher on islands than on forest. Plant and ant community, as well as interactions on islands and lake edge were nested with forest. Forest network was highly compartmented, while island and lake edge networks lost species, interactions and compartments and won new opportunistic ant species. Connectance didn’t change among habitats and was not related to islands traits. Natural history, landscape traits, ecological processes decay, coextinction, and new interactions were discussed as the main factors involved on nested communities, networks changes, species loss and connectance constancy of our community. Coextinction and interaction loss by dam fragmentation can influence evolutionary processes with important implications for conservation.