The climate is warming fast, threatening species persistence and biodiversity. Being sessile, plants must respond and adapt to changing environmental conditions in situ. In this regard, phenotypic plasticity is described as a rapid and adaptive mechanism to respond to changes in climate. However, despite widespread evidence of plastic responses to changing environments, very few studies tested whether these responses were also adaptive. In reality, many fundamental aspects of plasticity are still poorly understood. These fundamental questions can be divided into Ecological/Evolutionary questions, such as whether plasticity is adaptive, whether it confers resilience to climate warming and whether there is intra-specific variation in plasticity; and questions on the molecular underpinnings of plasticity, i.e., how gene expression or post-translational regulation, among other mechanisms, determine the phenotypic change. In the first part of my PhD, I focused on eco-evolutionary questions and investigated plastic responses of an alpine herb to projected warmer temperatures. I found significant plastic responses to warmer growth temperatures in many traits including thermal tolerance (hence, providing evidence for thermal acclimation), reproductive traits, and germination. However, these plastic responses did not confer resilience to warmer growth temperatures, since overall fitness was severely reduced under warming. We did not find evidence of significant intraspecific variation in plasticity among genotypes, suggesting canalised responses to temperature.

In the second part of my PhD, I used differential gene expression (DGE) analysis to compare molecular responses of tolerant and sensitive genotypes to warmer temperatures; then, I associated gene expression to phenotypic traits to identify genes potentially involved in thermal tolerance and plasticity. Under warmer temperatures plants up regulated heat-shock proteins and pathways related to RNA metabolism; whereas they down regulated many processes related to photosynthesis and genes encoding for photosynthetic components. This down regulation was stronger in tolerant genotypes suggesting a potential link of this response with higher thermal tolerance. Weighted correlation network analysis (WGCNA) revealed correlations between Fv/Fm, a parameter describing photosynthetic efficiency, and genes involved in photosynthesis and light reactions. Most of our knowledge on plant responses to high temperature stress comes from studies on Arabidopsis and rice. Application of genomic techniques to non-model species will enable ecological annotation of genes and identification of novel genes potentially involved in responses to stress.