Rare species play a much more important, and even unique, role in ecosystems than was previously thought, according to new research from the University of Montpellier 2. The research has found that many of the rarest species in the world, most of which are rapidly going extinct, play very important roles in many ecosystems and support unique ecological functions that aren’t provided by other species.
The new research, done by analyzing and comparing species function in three very different types of ecosystems, highlights the importance of many of the rapidly disappearing and rare species of the world, and the impact that the extinction of these species may have on ecosystems. Specifically, the research utilized data on coral reefs, tropical forests and alpine meadows; analyzing “the extent to which rarer species in the three different ecosystems performed the same ecological functions as the most common ones.”
What the research has demonstrated, and what is so important, is that it’s “primarily the rare species, rather than the more common ones, that have distinct traits involved in unique ecological functions.” With the disappearance of these species, and the overall decline in biodiversity, these unique ecological features are themselves likely to disappear.
“These unique features are irreplaceable, as they could be important for the functioning of ecosystems if there is major environmental change,” explained Dr Mouillot.
Previously it had been assumed that rare species had relatively little influence on the healthy functioning of most ecosystems, owing to their low numbers and limited range. It had been thought that they likely fulfilled the same ecological roles as more common species, and were “functionally redundant”, simply providing a backup in case of ecological loss. But as the new research has shown, that was a mistaken assumption.
The press release explains the methodology of the research:
To test this, the team of researchers analyzed the extent to which rarer species in the three different ecosystems performed the same ecological functions as the most common ones. They examined biological and biogeographical information from 846 reef fish, 2979 alpine plants and 662 tropical trees and found that most of the unique and vulnerable functions, carried out via a combination of traits, were associated with rare species.
Examples of such species supporting vulnerable functions include the giant moray (Gymnothorax javanicus), a predatory fish that hunts at night in the labyrinths of coral reefs; the pyramidal saxifrage (Saxifraga cotyledon), an alpine plant that is an important resource for pollinators; and Pouteria maxima, a huge tree in the rainforest of Guyana, which is particularly resilient to fire and drought. Not only are they rare but they have few functional equivalents among the more common species in their respective ecosystems.
“Our results suggest that the loss of these species could heavily impact upon the functioning of their ecosystems,” said Dr Mouillot. “This calls into question many current conservation strategies.”
“Rare species are not just an ecological insurance,” he said. “They perform additional ecological functions that could be important during rapid transitions experienced by ecosystems. The vulnerability of these functions, in particular biodiversity loss caused by climate change, highlights the underestimated role of rare species in the functioning and resilience of ecosystems. Our results call for new experiments to explicitly test the influence of species rarity and the uniqueness of combinations of traits on ecological processes.” This line of research will also inform the lively debate about the relationship between biodiversity and ecosystem functioning.