Ecology of Batrachochytrium dendrobatidis and tadpole assemblages in the Northeastern Atlantic Forest

Abstract

Amphibians are very diverse and abundant in tropical ecosystems and they have been rapidly declining worldwide in the last decades. Declines have been associated mainly with habitat loss, climate alterations and diseases that have negative effects in the amphibian communities. In this study were evaluated the ecology of Batrachochytrium dendrobatidis on tadpoles in the Northeastern Atlantic forest and how biotic and abiotic descriptors are influencing tadpole assemblages. For the first goal we quantified Bd infection dynamics on tadpoles of two breeding hosts. Bd prevalence varied seasonally, and tadpoles of Aplastodiscus sibilatus and Proceratophrys renalis were Bd positive found in both seasons, while tadpoles of Agalychnis granulosa were Bd infected only during the rainy season. Larger individuals had a higher probability to be Bd positive independent of developmental stage. Besides, environmental factors such as canopy cover, stream flow, water temperature, stream depth, pH and host density were associated with the Bd prevalence. Both tadpoles and streams could be reservoirs of the pathogen, thus monitoring frog populations in these habitats is necessary to assess the impact of this pathogen in this biodiversity hotspot. For the second goal, were studied tadpole assemblages in temporary and permanent ponds to determine the variation on their composition and abundance in the ponds and to measure the influence of biotic and abiotic factors shaping. Tadpole species richness was explained by environmental and biological variables through General Regression Models. The relationships between the tadpole assemblages and predictors on their spatial variation were measured using a Canonical Correspondence Analysis (CCA). Tadpole richness differed between ponds, although abundance did not. Depth and water temperature were related to tadpole richness, while canopy cover, dissolved oxygen, richness of predators and water temperature were related to tadpole abundance. In the CCA analysis depth, dissolved oxygen, richness predator, canopy cover and water temperature explained the tadpole assemblage structure in permanent and temporary ponds.