Impacto dos fatores antropogênicos e ambientais na dinâmica do microbioma e nas interações hospedeiro-patógeno em anfíbios

Abstract

Amphibians are among the most threatened vertebrates, with 41% of species at risk of extinction due to habitat loss, climate change, invasive species, and emerging diseases. A key factor influencing their health is the skin microbiota, a community of symbiotic microorganisms that contribute to immunity and disease resistance. However, this microbiome is highly sensitive to environmental disturbances, which can alter its composition and reduce its protective functions. One of the major threats to amphibians is chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd), a pathogen that disrupts skin integrity and weakens host defenses, leading to high mortality rates. This infection interacts with environmental stressors, including pollution and habitat degradation, increasing amphibian vulnerability. This thesis explores the composition and ecological drivers of amphibian skin microbiota, its interactions with Bd, and the effects of environmental disturbances. The results show that microbiome diversity varies across species, seasons, and environmental conditions. A case study on Bd dynamics across different species and environmental conditions demonstrated that infection prevalence and load were lower in warmer temperatures and in species with non-aquatic habits, suggesting that abiotic factors and host ecology significantly influence Bd susceptibility. Furthermore, seasonal variations in microbiota composition were observed, with microbial diversity generally decreasing in colder months. These seasonal shifts could be linked to changes in amphibian behavior and immune function, highlighting the need for long-term monitoring of microbiota-host-pathogen interactions. In conclusion, this thesis provides novel insights into the complex interactions between amphibian microbiota, environmental changes, and disease dynamics. Understanding how anthropogenic disturbances and seasonal variations shape microbiome diversity is essential for developing effective conservation strategies. Future research should focus on longterm monitoring of amphibian microbiomes, explore the role of larval-stage microbiota in pathogen resistance, and investigate microbiome-based interventions to support amphibian populations facing increasing environmental threats.