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w 10 | Live from the Labs cnrs I international magazine Biodiversity Researchers have discovered that key traits of rare species are essential for the balance of ecosystems. Preserving them, through Marine Protected Areas (MPAs), for example, is more crucial than ever. BY Fui Lee Luk w An international team1 has shown that rare species perform unique ecological functions that sustain overall ecosystem stability. Rare species—those found in low numbers or limited in geographical distribution— are often the first to go extinct when human development threatens global flora and fauna. Yet their loss means far more than reduced biodiversity and number of species. According to a new study2 spanning three rich ecosystem types—coral reefs, alpine meadows, and tropical forests—many rare species provide irreplaceable vital ecological functions. The smooth running of an ecosystem relies on the input of its species, whose role depends on their biological traits, such as diet and flying ability for animals, or soil preference and water intake for plants, for example. Assumed to merely back up the role played by common species, rare ones were long thought to have little impact on ecosystem functioning. The present study shows otherwise. Examining 846 South Pacific coral reef fish, 2979 French alpine plants, and 662 Guianese tropical trees, researchers indexed biological and biogeographical data on species traits and rarity in the three ecosystems. The team found that the most unusual combinations of traits invariably belong to rare species, which therefore contribute unique functions in ecosystems. The giant moray eel, for example, hunts sea creatures in hard-to-access reef labyrinths; the pyramidal saxifrage plant is a key pollen source on barren alpine cliffs; and the highly-resistant Pouteria maxima tree helps rainforests withstand fire and drought damage. Simply put, these rare species perform functions that common species cannot. While evolution may help fill functional gaps when rare species disappear, “evolutionary recovery of functions occurs at a longer time scale than extinction rates,” says David Mouillot, team leader of the Ecosym3 laboratory. At a time when climate change and human expansion could be putting entire ecosystems at risk, the role played by these rare species may be crucial for future ecosystems operating under different environmental conditions. The researchers will now urge ecology experts to take into account the unique roles played by rare species when drafting viable conservation strategies. The loss of these species would disproportionally imperil the long term sustainability of ecosystem functioning upon which human welfare depends. 01. Involving researchers from France, the US, the UK, and Australia. 02. D. Mouillot et al., “Rare species support vulnerable functions in high-diversity ecosystems,” PLoS Biol., 2013. 11(5): e1001569. 03. Écologie des systèmes marins côtiers (CNRS / Université Montpellier I and II / IRD). Minorities that Count Contact information: Ecosym, Montpellier. David Mouillot > david.mouillot@univ-montp2.fr 01 01 02 Giant Morays (left) perform key ecological functions by hunting in difficult-to-access coral reefs (right). 03 04 The massive tree Pouteria maxima which is found in French Guiana's tropical forest (right) has sturdy and thick leaves that can resist drought and fire. 03 02 04 © photos : C.E.T. Paein © photos : J.P. Kaeijkrsw Montpellier


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