Abstract: The sub-Antarctic islands are facing rapid and intense climate change but their isolation also means that dispersal between islands is unlikely to offer an escape route for their floras. Instead the plants on these islands will need to adapt in order to survive. Autochthonous plant species from the Kerguelen Islands are adapted to harsh ecological conditions that include low temperatures, consistent rainfall, and salt spray. These species, especially when growing close to the extremes of their ecological range, may be particularly sensitive to climate change and indeed already exhibit signs of stress during dry summer periods.
In our previous studies we found that species endemic to the Kerguelen province exhibit strong phenotypic integration (i.e. their traits are strongly correlated). Such integration may limit their ability to respond to climate change. The current study focuses on patterns of trait variability and phenotypic integration across abiotic and biotic gradients. Our aim is to estimate the capacity for plastic and adaptive responses in sub-Antarctic plant species.
We performed in situ measurements and experiments in controlled chambers. We measured plant traits and metabolites in situ in populations occupying habitats that differed in both abiotic (pH, conductivity, water saturation) and biotic (diversity of surrounding community) parameters. Populations growing in different environmental conditions show differences in both levels of trait variability and phenotypic integration. We also examined the interactions between these two components and the environment. Experiments characterized tolerance to different combinations of abiotic conditions (light, temperature) using seedlings grown from seed collected on the Kerguelen Islands and those from plants cultivated in growth chambers. We determined trait variability and phenotypic integration within and between populations grown under different conditions.
The significance of phenotypic integration in determining a species ability to adapt to environmental change is not known yet. This goal requires further analyses to determine the relationship between phenotypic integration and plant performance. Understanding this relationship will help to predict the outcomes of climate change for Kerguelen plant species. Considering that environmental changes are more severe at higher latitudes, these insights could be important for the conservation of autochthonous sub-Antarctic species.