Ecologists struggle to get a grip on the term, ‘keystone species’

Ecologists struggle to get a grip on the term, ‘keystone species’

Lesley Evans Ogden writes:

Anne Salomon’s first week as a graduate student in 2001 was not what she had anticipated. While other new students headed to introductory lectures, Salomon was whisked away by van and then motorboat to Tatoosh Island, which sits just offshore of the northwestern tip of Washington’s Olympic Peninsula. Among the tide pools of this isolated island, Salomon peered at the web of life on the rocks: ochre sea stars, barnacles, mussels, snails and assorted algae that took forms reminiscent of lettuce, moss and bubble wrap.

A visit to this wave-pummeled outcrop was a rite of passage for lab associates of Bob Paine. Decades earlier, Paine, armed with a crowbar, had first pried purple Pisaster starfish — the ecosystem’s top predator — from tide pools in nearby Makah Bay and flung them into the sea so he could learn what forces organized the community of rock-clinging creatures. The results would profoundly influence ecology, conservation and the public perception of nature. After three years without starfish, the 15 species originally present in the pools declined to eight. After 10 years, a mussel monoculture dominated the shore.

The results of Paine’s experiment, published in The American Naturalist in 1966, showed that a single species can have an outsize influence on an ecological community. When Paine shared his findings with the paleoecologist and conservationist Estella Leopold, she suggested that a powerful concept deserved an evocative name. In a subsequent paper, he designated the Pisaster starfish a “keystone species,” referring to an architectural keystone: the wedge-shaped stone atop an arch that, once inserted, prevents the structure from collapsing. “Bob had a fairly poetic, narrative mind,” said Mary Power, an emeritus professor at the University of California, Berkeley who studied under Paine. (Paine died in 2016.)

Salomon, Power and other Paine students dedicated their graduate work to refining the keystone concept and defining a species’ ecological “keystone-ness” mathematically. But like starfish glomming onto rocks, the metaphor took hold in the scientific and public imagination. Many ecologists and conservationists lost sight of the original significance Paine had given to the term and began branding seemingly every important species a keystone. Indeed, an analysis published last year found that over 200 species have been marked as keystones. Usage of the label has become so broad that some ecologists fear that it has lost all meaning. [Continue reading…]

Comments are closed.