Distribuição e diversidade de hifomicetos aquáticos em riachos Neotropicais.

Abstract

Stream ecosystems depend on aquatic fungi because they are the main decomposers of organic matter in these environments. Thus, these fungi link the allochthonous material of the surrounding vegetation and the stream biota. Also, these fungi rely on landscape conditions for the community structure and composition. A protected area should present better habitat quality than a heavily human impacted area. Parque Nacional Campos Gerais (PNCG) which is the largest protected area from the Araucaria moist forest, an evergreen subtropical moist forest. This forest is part of the Atlantic Forest, one of the main global biodiversity hotspots because of intense anthropic impacts and high occurrence of endemic species on the biome. Practically two thirds of all Brazilian population dwell in this biome and impacts are diverse. Beyond the importance of riparian vegetation and landscape features, studies have shown that freshwater fungal community depends on environmental variables, but, the main scale determining its richness and abundance is not certain. This work, divided in two parts, compares in the first part, fungal communities from an area which suffers less human impacts (inside a Nature Reserve, NR) with an area which suffers more intense impacts (in a surrounding farmland). Considering that diversity indices allow us to compare distinct communities, our hypothesis was that Shannon-Wiener, Pielou evenness and ?-diversity are higher inside a NR than in a farmland. The second part aimed to evaluate which scale (microscale or macroscale) was the most predominant in determining the aquatic fungal community. Considering that environmental variables measured directly at the leaf banks in the streambed (from which fungi samples were collected) probably are more related to the community composition, our hypothesis was that microscale is more determinant than macroscale. For that, we collected leaves from the streambed inside and outside PNCG and analysed them in the laboratory. Both hypotheses were rejected. We concluded that nutrient concentration differences may have determined the high values of the diversity indices outside the park. Also, ammonia and conductivity are the variables that most influenced the fungal community in the macroscale. Altogether, each stream must be considered a singular system for its characteristics influence more fungal community than variables from the leaf banks. We registered new occurrences from Brazil (34) and from the Atlantic Forest (42). Finally, aquatic fungal community conservation in the investigated ecosystem must be ensured including the highest possible number of streams in the protected area. Conservation actions must be implemented to comprise the watershed as a whole in an attempt to protect it from urban and rural impacts. Only with protective approaches impacts will be minimised and ecosystem services and environmental quality ensured in the long term.