Climate and intraspecific variation in a consumer species drive ecosystem multifunctionality

Climate change is altering the multifunctionality of ecosystems worldwide and is often associated with changes in biodiversity that can modulate the impacts of climate change on ecosystems through interactive effects. Genetic and phenotypic variation within species are particularly influenced by climatic conditions, and can mediate several ecosystem processes. Here, we tested whether temperature can interact with intraspecific variation to drive ecosystem multifunctionality. Using a common gardening experiment, we test the consequences of intraspecific variation (population identity and trait variation) of a consumer fish species (European minnow Phoxinus phoxinus) and temperature on ecosystem multifunctionality, as well as on the biomass of a subsequent fish generation (long-term effects). We found that individuals from different populations affect ecosystem multifunctionality independently of temperature, and that multifunctionality differed between cold and warm mesocosms. Moreover, when investigating sub-components of multifunctionality, we found a positive relationship between individual metabolic rate and multifunctional primary production in warm mesocosms, whereas this relationship was reversed in cold mesocosms. We similarly found evidence that the long-term effect of intraspecific trait variation on the biomass of the next fish generation was temperature-dependent. These findings demonstrate that differences among populations can have strong consequences on ecosystem multifunctionality, and that intraspecific variation must be considered in addition to other components of global change to predict the impacts of global change on ecosystem multifunctionality.