Biological invasions and climate change are among the main drivers of global scale transformations; the effects of which are felt every day on our planet. Exotic species can alter the composition and structure of native communities and the functioning of ecosystems, eliminating the services they provide. In addition, they are among the main causes of biodiversity loss in the world, a situation that is amplified in habitats and ecosystems that are especially vulnerable under changing climatic conditions. Faced with this scenario, our team believed it was important to anticipate how the effects of climate change that are predicted to occur in southern Europe would affect the behaviour of Carpobrotus edulis, one of the worst invasive plants affecting our coastal ecosystems. We also set out to find out if this species has the ability to undertake rapid evolutionary changes that would allow it to accelerate the processes of adapting to new territories and environmental conditions.
Iceplants, as they’re commonly known, are native to South Africa and have been widely used as ornamental plants in temperate zones around the world due to its showy flowers. They were also used to stabilize hillsides and slopes thanks to its rapid growth, even under extreme conditions like high salinity and temperature, and little water and nutrient availability. Currently C. edulis has uncontrollably invaded coastal areas in Europe, America and Oceania, some of which are especially vulnerable, and where considerable economic and human resources have been devoted to its control and eradication.
We conducted our recently published study in an experimental plot on the Island of Sálvora, in the Parque Nacional das Illas Atlánticas de Galicia, in the northwest of Spain. We set up small open top chambers made up of methacrylate to simulate the increase in temperature as well as some water collection channels to mimic the effect of decreasing precipitation. By installing an exhaustive network of soil and air sensors inside 32 sub-plots (8 control, 8 with increased temperature, 8 with decreased precipitation and 8 with a combination of both) we were able to confirm that the conditions of humidity and temperature were those we expected. In our study we included plants from 4 South African populations (native) and 4 populations from the northwest of the Iberian Peninsula (invasive), where this species has lived for more than 100 years.
For more than a year, our team measured physiological traits and collected data related to survival, growth and biomass allocation. In addition, we carried out exhaustive biochemical analyses to determine pigment and antioxidant contents as well as plant hormones related to stress.
In our recent publication in the American Journal of Botany, we report that higher temperatures resulted in increased relative growth rates and higher photochemical efficiency of C. edulis, which shows that this species has effective mechanisms to cope with climatic changes that have been predicted for southern Europe. The effects of decreasing precipitation were not as strong as those of rising temperature, although precipitation modulated its effect. Thus, it is expected that the new climatic scenarios will promote the invasion of C. edulis favouring its establishment and dispersal in the invaded areas.
In our study we also found differences between South African (native) and Iberian (invasive) populations in terms of their survival and functional traits, with Iberian plants showing the greatest capacity to adapt to new climatic conditions. This shows that plants of the invaded region would have evolved in response to the selective pressures experienced in their new environment, diverging from the native plants. Previous studies have already documented evolutionary changes in invasive species just a few decades after being introduced into new territories. Such changes can accelerate adaptation processes by enhancing the efficiency of plants to invade the ranges into which they’re introduced.
This study makes clear that iceplants hold useful strategies in their toolbox that will allow them to face climate change scenarios — something that poses a serious threat to the integrity of the communities they invade.
Margarita Lema is an ecophysiologist at the Department of Functional Biology at the University of Santiago de Compostela, with interests in understanding the physiological response of plants to biotic and abiotic factors. Her research involves the study of the ecophysiology and management of plant genetic resources, use of physiological traits for plant breeding and early stress detection in forest and crop species, comparison of ecophysiological traits of wild and cultivated species and climate change effect on ecophysiology of native and invasive plant species. She is also concerned in exploring strategies to teach science effectively. You can read more about her work here.
English translation by Lorena Villanueva Almanza