The evolutionary role of epigenetic mechanisms : the adaptation of freshwater organisms to climate change

• Autor(a) principal: Jeremias, Guilherme de Abreu
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/22025
• topic: Organismos aquáticos; Ecologia de água doce; Epigenética

Freshwater is a precious resource for humankind. Nevertheless, freshwater systems face not only significant anthropogenic pressure but also numerous transformations induced by climate change. Nowadays, climate change is recognized as a serious threat to freshwater ecosystems and, on a global scale, freshwater biodiversity is in rapid decline. In the last few years, epigenetics has been gaining importance in several scientific fields, such as human health and developmental biology. In fact, epigenetic mechanisms can influence phenotype determination and epigenetically acquired phenotypes are known to be inherited across several generations. Therefore, epigenetics is a promising but unexplored topic in a significant number of scientific fields. Taking into account that the global aim of this work was to explore the resilience of freshwater species to cope with the environmental transformations induced by climate change, its main specific objectives were: i) to review the impacts of climate change on freshwater ecosystems, and explore the link between epigenetic mechanisms and the adaptation of different species to the associated phenomena; ii) to assess the relevance of epigenetic mechanisms in the adaptation of Daphnia magna to an increase in water salinity. An extensive review was made leading to the conclusion that climate change is transforming the composition, biodiversity and functioning of numerous freshwater ecosystems. Additionally, this study highlighted that, in the context of climate change, the rise in water temperature and/or salinity are the major threats to freshwater biodiversity, while epigenetic mechanisms can have a decisive role in constraining both short- and long-term adaptation of different taxonomic groups to the environmental transformations induced by climate change. As the second objective was tackled, the exposure of one generation of Daphnia magna to increased salinity showed that there is a molecular adaptation to the hyperosmotic environment at the epigenetic level. For some genes, this epigenetic adaptation was transferred across three successive generations, none of which exposed to the stressor challenging the parental generation. Generally, this work supports the idea that epigenetic mechanisms are a promising topic in the fields of aquatic toxicology and evolutionary biology, as well as in research undertaken in their intersection.