Everything you thought you knew about keystone sea stars is wrong

…ok, maybe not everything. I’m just getting into the clickbait title fad. But you probably are incorrectly citing Paine (1966), so you’ll be glad you clicked!

Bob Paine, a giant in ecology, recently passed away. He left behind an incredible legacy of ideas and students, and one insanely famous paper: “Food web complexity and species diversity.” If you’re an ecologist, you know that in the experiment described in that paper, Paine removed sea stars from the rocky intertidal and then recorded what happened. In particular, when sea stars were removed, he found that mussels (a favorite delicacy of sea stars) took over more of the primary substrate, crowding out other space-holding species and thus reducing the total number of space-holding species.

According to a recent paper by Lafferty and Suchanek (2016)(PDF link), ecologists usually cite Paine (1966) when they say something like, “predators increase biodiversity by fostering co-existence among competitors.” Most papers never specify which components of biodiversity actually increase when sea stars are present (i.e., primary space-holders). But it turns out that it is important to be specific, because in the rocky intertidal, sea stars actually greatly reduce biodiversity! By eating mussels, sea stars reduce the surface area of an important 3D habitat full of epibionts and parasites and tiny free-living organisms that live among the mussel shells. So, when you cite Paine (1966), you should specify that sea stars increase primary space-holder biodiversity, but reduce total community diversity.

As a side note, my favorite quote from this paper was: “Whelks are like little wolves in slow motion.” Go read it!


Those purple things are mussels. You get the cartoons you pay for on this blog. 😛


Lafferty, K.D., and T.H. Suchanek. 2016. Revisiting Paine’s 1966 Sea Star Removal Experiment, the Most-Cited Empirical Article in the American Naturalist. The American Naturalist.