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15 juin 2016 3 15 /06 /juin /2016 15:09

L'EVE DES CACHALOTS. Une femelle ayant vécu il y a quelques dizaines de milliers d'années a imposé son génome dans l'Océan mondial jusqu'à aujourd'hui. Hakai Magazine, hier. John .R. Platt. Sperm Whales have an "Eve".


Etude d'Alana Alexander et six collaborateurs, publiée le 2 mai dernier dans Molecular Ecology.

Sperm whales have existed for millions of years, but Alexander’s research suggests that Eve only appeared on the scene in the past 10 to 80 thousand years. How she came to dominate the sperm whale family tree remains a mystery. Alexander says the research suggests that at some point Eve and her descendants out-competed other females—though it’s unclear how—and spread their genetic lineage throughout the world.

The fact that Eve’s DNA has been found all over the world opens up additional questions. Today, only male sperm whales travel far from where they are born. Females tend to stay put, so Eve’s mitochondrial DNA should have as well. But, for some reason, it didn’t.

The new genetic study also reveals that the current lack of female sperm whales migrating puts a limit on genetic flow for the species—an issue in the face of anthropogenic climate change and other threats, which are isolating sperm whales into smaller, geographically isolated sub-populations. Populations in Eve’s time may have been more able to mingle with each other over time. That opportunity is now no longer available.

Alexander says this suggests that management strategies for sperm whales may need to prioritize females, not necessarily populations as a whole. If all of the females in a given location die out, it now appears unlikely that any new females would migrate to replace them.

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