Robert Treat Paine III (1933-2016).

Robert Treat Paine III passed away June 13 in Seattle surrounded by family and friends. RTP, as he was known, was an emeritus Professor at the University of Washington, where he developed a career that helped define the field of community ecology. Ever an avid naturalist who paid close attention to the specifics of a bird song or a starfish’s diet, RTP’s best-known contributions were the concepts of keystone species and trophic cascades. Keystone species have effects on communities or ecosystems that are much larger than their abundances would suggest. Trophic cascades are the many changes in species diversity or abundance that ensue when a consumer is removed from an ecosystem (see ref. 1 for a more detailed synopsis). RTP was also well-known as a champion of the use of experimental methods in field ecology, helping to show that simple experiments in complex natural communities could reveal a wealth of information about how species interacted with one another. Another enduring dimension of his legacy was his mentoring and inspiration of several generations of graduate students and postdocorates in the adventure of working out the complex wiring of species interactions, all within the wild dynamics of natural ecosystems. RTP was a descendent of a celebrated clan in Boston that included Thomas Paine and Robert Treat Paine Sr., a signer of the US Declaration of Independence, as well as the great mathematician George Birkhoff. RTP grew up in Boston as an avid naturalist and bird watcher, and attended Harvard. His initial graduate work was in paleontology at the University of Michigan, but he became fascinated by ecology in courses led by ecologist Fred Smith, so ended up doing an ecological study of a modern-day brachiopod. After a postdoctorate at The Scripps Research Institute in San Diego, California, he took a faculty position at the University of Washington, where he began working on the complex invertebrate communities of the highly productive and species-rich northeastern Pacific intertidal zone. In the welter of the interactions of hundreds of species, RTP focused on predator–prey interactions, charting out the species that were consumed by others. In this, RTP found a simple metric for predation by a large abundant species: By turning over purple sea stars, he could record the diets of hundreds of individuals. This led to a simple question about the impact of predation on intertidal communities, which RTP studied by experimentally manipulating densities of purple sea stars along rocky shores. The fundamental changes in communities without stars focused RTP on the role of predators controlling community composition. Some species could be removed without huge effect. Others were key to community composition, and without them the communities collapsed. From this realization, RTP used the analogy of a keystone—the central shaped stone holding up an arch—to describe the importance of keystone predators. In a short note published early in 1969, RTP coined a term that has since become intrinsic to the lexicon of ecology (2). RTP’s gift was to take a simple field experiment on marine invertebrates and turn it into a broad lesson in ecological organization that struck a chord across Robert Treat Paine III. Image courtesy of Robert Steneck (University of Maine, Orono, ME).