Scientists Repeat Century-Old Experiment to Reveal Evidence of Evolutionary Rescue in the Wild

A microscope image of the intertidal flatworm Procerodes littoralis.
Credit: Katharine Clayton, University of Plymouth

A tiny flatworm found commonly on the coasts of western Europe and North America is living proof that species may be able to evolve and adapt to rapid climate change.

Research by the University of Plymouth examined the extent to which the intertidal flatworm Procerodes littoralis was able to regenerate and repair itself when challenged with different seawater conditions.

Repeating a study conducted more than a century earlier it was shown that the response of individuals had changed markedly since then.

The original study was conducted by Dorothy Jordan Lloyd, who was based at the Marine Biological Association in Plymouth, and focussed on individuals found in Wembury Bay, Plymouth.

It was published in 1914, and the current study — led by BSc (Hons) Marine Biology graduate Katharine Clayton — replicated it in terms of the processes followed and the precise locations from which samples were collected.

When tested across a range of different concentrations of saltwater in the laboratory, scientists showed the flatworm was able to regenerate following minor injuries at lower salinities than were recorded originally.

They also demonstrated that while in 1914 there was an optimum salinity level for individuals to regenerate this is no longer the case, suggesting individuals have extended their tolerance range in the intervening 104 years.

Scientists also examined rainfall levels for the Wembury Bay area and found they had increased between 1914 and 2018, which is likely to result in exposure to lower salinities in the intertidal region, where the flatworm is found.

Put together, they say it shows how individual species may be able to adapt and survive the localized effects of climate change which, if correct, provides some of the first evidence of evolutionary rescue taking place in the wild.

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