Response of aquatic plant communities of the Iles Kerguelen (sub-Antarctic) to climate change.

• Main Author: Douce, Pauline
• Other Authors: Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés (LEHNA), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École Nationale des Travaux Publics de l'État (ENTPE)-Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard - Lyon I, Anne-Kristel Bittebiere
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2023
• Subjects: Intraspecific trait variability; Spatial patterns; Mesocosm; Eco-evolutionary dynamics; Community assembly mechanisms; Aquatic systems; Macrophytes; Iles Kerguelen; Variabilité intraspécifique des traits; Patrons spatiaux; Mésocosme; Dynamiques éco-évolutives; Mécanismes d'assemblages des communautés; Systèmes aquatiques; [SDV.EE]Life Sciences [q-bio]/Ecology; environment; Antarc*; Antarctic
• Online Access: https://theses.hal.science/tel-04504717; https://theses.hal.science/tel-04504717/document; https://theses.hal.science/tel-04504717/file/TH2023DOUCEPAULINE.pdf

The effects of increasing temperatures are especially severe in aquatic plants, which are a resource and a habitat for a large variety of organisms. However, the dynamics of aquatic plant (macrophytes) communities in the context of climate change remain poorly studied. In the literature, the functional responses of plant species to thermal stress and plant-plant interactions are generally studied separately, while these species are subjected to them simultaneously in their habitat. These variations in the functional composition of communities could impact the coexistence mechanisms between plant species, as well as productivity and biogeochemical cycles at the ecosystem scale, with possible feedbacks on the phenotypic evolution of species. In this context, this thesis aims to assess how increasing temperatures modify macrophyte community dynamics and consequently aquatic ecosystem functioning, taking the role of intraspecific variability in species response and effect traits into account. The research questions of this thesis were addressed through in situ and controlled condition approaches, on the model of freshwater ponds of the Iles Kerguelen, located along the coast, in the sub-Antarctic region. Our results show that there is habitat heterogeneity between ponds in relationship with variations in temperature and nutrient availability. These habitat parameters are the most structuring for macrophyte communities, and determine their performance through their direct effects, or through the modulation of plant-plant interactions and biotic parameters such as spatial patterns. At the species scale, we showed an interactive effect of temperature and plant-plant interactions on functional traits in one of the studied species. Furthermore, changes in the phenotype of individuals, particularly at the foliar level, impact the ecosystem process of litter decomposition. By feedback, these ecosystem modifications affect the phenotype of the individuals, highlighting the existence of an eco-evolutionary loop based on ...