Since the opening of the Suez Canal in 1869, many fish species from the Indo-Pacific basin have invaded the Mediterranean. A third of them have colonised waters that are cooler than those of their original habitat, thus extending their climatic niche. These results suggest that the expansion of marine species in response to climate change has so far been underestimated. The results come from the research conducted by an international team from IRD’s CoReUs unit (now part of the ENtropie joint research unit) and the CRIOBE (Insular Research Center and Environment Observatory – CNRS/Perpignan University/EPHE). The study featured on the front page of the March 2015 edition of Ecology Letters magazine.
In 1869, the Suez Canal created a direct link between the Red Sea and the Mediterranean, and the latter involuntarily became the site of the world’s largest invasion of species. More than 90 fish species from the Indo-Pacific basin have thus made their way into the Mediterranean since then. But does this colonisation match their original climatic niche? To find out, French, Italian and Israeli researchers put together more than 800 scientific papers on spatial distribution in the Mediterranean and the Indo-Pacific basin, looking at 30 invasive fish species; the frequency of observation for other species was not considered reliable.
The scientists were able to demonstrate that 33% of these 30 tropical species settled outside their climatic niche, in much cooler waters (differences of up to 6°C) than in the areas where they were geo-referenced. These climatic niches now provide the basis for models used to predict biological invasions and the effects of climate change on the distribution of species. ‘In a terrestrial environment, these predictive models appear reliable. In a marine environment, our results suggest they significantly underestimate the potential expansion of invasive species,’ explains Valeriano Parravinci, a research lecturer at CRIOBE and the study’s first author.
In fact, other than climatic niches, it would also be useful to include the ecological niches of marine species in these models. ‘It is vital that new factors are integrated: currents that can carry larvae hundreds of kilometres, biological interactions and the potential competition between species,’ the researcher explains. In the Mediterranean, some tropical fish species more used to fierce competition in the Pacific have not come up against many ‘rivals’, while others have found plenty of food.