Large diversity in new keystones list challenges predominant belief

New research on the planet’s ‘Keystone Species’ has revealed a staggering and unappreciated diversity in what kind of animal fits this distinguished label.  Defined as those species that have enormous influence on ecosystems relative to their abundance, the stereotypical Keystone Species that frequently come to mind are large predatory mammals, like the recolonizing wolves that changed the Yellowstone area. 

But a new peer-reviewed paper in Ecology and Evolution challenges this stereotype. Presenting the first evidence-based list of animal keystones, a team of scientists from Canada and the US reveals a wide diversity of the planet’s keystone species in terms of their size, shape, and functional role. The prominence of many smaller species on the list, like cabbage butterflies and pocket mice, challenges the prominent belief that all keystones are large carnivores. 

“We’ve all heard of the Yellowstone wolves, but they’re just part of the story. Many keystones are much smaller, and instead of influencing ecosystems via predation, they perform important ecosystem services such as churning up soil or filtering water”, says Ishana Shukla of the University of Victoria and Raincoast Conservation. Shukla and her team identified 230 keystone animals from 1800 scientific papers. Their analysis found that large carnivores are just one of five keystone ’archetypes ’, with other archetypes comprising small marine invertebrate modifiers, insects consumers, fish consumers and rodents modifiers.

This new Keystone Species list has applied value. While large carnivores have played center stage in conservation debate for decades, many smaller keystones have been overlooked. Investing resources to protect the broader range of keystones reduces risks that overlooked keystones are lost from ecosystems, which can impose devastating effects on nature and, eventually, humans. ‘While we might tend to forget about these less charismatic species, targeting them for conservation helps the entire system, giving those who invest in conservation great bang for their buck!’

Citation

Shukla, I., Gaynor, M. K., Worm, B., & Darimont, T. C., (2023). The Diversity of Animals Identified as Keystone Species. Ecology and Evolution  https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.10561

Abstract

Although the keystone species concept was conceived of over 50 years ago, contemporary efforts to synthesize related literature have been limited. Our objective was to create a list of keystone animal species identified in the literature, and to examine the variation in the traits of species and the ecosystem influences they elicit. We documented 230 species considered keystones. A clustering analysis classified them into five archetypes based on combinations of their taxonomic class, body size, trophic level, and role (consumers, modifiers, or prey). Whereas conservation and public perception of keystones primarily focuses on large vertebrate consumers, our analysis reveals that researchers have defined a wide diversity of keystone species, with large variation in associated ecosystem processes. Future research may confront ambiguity in definition of keystone status, as well as clarify the type, abundance, and quality of data required to assign the term. Identifying keystones with increased rigor would not only enrich the literature but also inform intervention to safeguard threatened keystones and their associated influences on ecosystems. 

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Authors and affiliations

Ishana Shukla; Department of Geography, University of Victoria, BC, CA V8W 2Y2 7 
Kaitlyn M. Gaynor, Departments of Botany and Zoology, University of British Columbia, 9 BC, CA, V6T 1Z4 10 
Boris Worm, Department of Biology, Dalhousie University, NS, CA, B3H 4R2 12 
Chris T. Darimont; Department of Geography, University of Victoria, BC, CA V8W 2Y2 14 and Raincoast Conservation Foundation 

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