🪸 Some corals programmed to survive extreme climate changes

The survival of certain coral ecosystems in the face of current climate upheaval finds an unexpected explanation in their distant past. An unprecedented genetic mapping, covering hundreds of species, reveals an evolutionary history marked by remarkable resilience during ancient environmental crises.

These marine organisms, pillars of ocean biodiversity, reveal adaptive capabilities inherited from hundreds of millions of years of evolution.


This comprehensive phylogenetic analysis, published in the journal Nature, traces the origin of hard corals to a remote era. The study demonstrates that these animals have already overcome extreme episodes of warming and ocean oxygen depletion. Their evolutionary trajectory, reconstructed through partial sequencing of numerous genomes, highlights distinct survival strategies that could prove decisive today.

A revisited evolutionary history

The common ancestor of contemporary hard corals lived approximately 460 million years ago. This organism, likely heterotrophic, exhibited notable ecological flexibility, allowing it to colonize varied habitats, from shallow waters to marine depths. This initial plasticity appears to have constituted a fundamental evolutionary advantage. The colonization of diverse ecological niches facilitated the dispersal and persistence of these species throughout geological eras, laying the foundation for their future diversification.

A decisive step in coral evolution occurred approximately 300 million years ago, with the establishment of a symbiotic relationship with photosynthetic algae. This biological innovation, by providing access to an additional energy source, catalyzed a major evolutionary radiation. However, fossil data indicate that many symbiotic lineages underwent mass extinctions during oceanic anoxic events 180 million years ago. This symbiotic dependence proved to be a point of vulnerability during global disturbances.

In striking contrast, non-symbiotic species persisted, and sometimes even thrived, during these same critical periods. Their survival is attributed to their energy independence and their ability to occupy deep habitats, less affected by surface crises. Their feeding regime based on capturing suspended particles offered them superior adaptability in the face of rapidly changing environmental conditions.

Perspectives for modern reefs

The main lesson of this study lies in the demonstration of differential resilience among coral lineages. Non-symbiotic corals, although less visible than their reef-building tropical counterparts, represent an invaluable genetic heritage. Their evolutionary history shows a proven capacity to survive planetary upheavals. Their presence in current marine ecosystems constitutes a reservoir of biological diversity that is crucial for the long-term survival of corals.

For modern symbiotic species, which form the backbone of coral reefs, the situation is more complex. Their dependence on stable environmental conditions makes them particularly vulnerable to bleaching induced by water warming. However, understanding their evolutionary history, marked by cycles of expansion and contraction, invites a reevaluation of their long-term adaptation potential. Their genetic heritage might contain latent tolerance mechanisms.

The conservation of coral ecosystems must therefore integrate the protection of this functional diversity. Preservation strategies benefit from including not only the emblematic reefs of warm, shallow waters but also the coral communities of colder and deeper waters. Safeguarding the entire ecological continuum occupied by corals maximizes the chances of maintaining essential ecosystem functions in a changing ocean.