Welcome to the Quanta Audio Edition.

In each of these bi-weekly episodes, we bring you a story direct from the Quanta website

about developments in basic science and mathematics.

I'm Susan Vallett.

The biological world is full of chemical signals. Ants lead their nestmates to food with winding trails of pheromones.

Plants exude aerosols to warn their neighbors of herbivores.

And everything you experience as smell is a molecule latching onto your nose.

And these so-called keystone molecules can build a web of invisible interactions among species.

That's next.

Quantum Magazine is an editorially independent online publication supported by the Simon's Foundation

to enhance public understanding of science.

In the biological world, some chemical signals find their targets, leading an aunt to a mate, saving a plant neighbor from

danger, or saving ourselves from getting sick from rotten leftovers.

Still, most of those chemical cues linger unread in the environment.

But sometimes other species, chemical eavesdroppers, bystanders or visitors, can pick up and interpret the

signals in their own way. If the message is powerful enough, the impact can ripple out across

an ecosystem. In 2007, biologists named these potent molecules after a popular concept in ecology. Keystone species, such as starfish

in Pacific Northwest tide pools, aren't abundant, but they have outsized effects on the food web,

making those species as crucial to their ecosystems as a load-bearing keystone in an archway.

The idea is, if they're removed, the entire

ecosystem could collapse into a different form. So keystone molecules are rare chemicals that can

structure, shape, and alter connections between species across entire ecosystems. It was a promising

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