GC: npl

S: http://education.nationalgeographic.org/encyclopedia/keystone-species/ (last access: 21 February 2016); http://cordis.europa.eu/project/rcn/67685_en.html (last access: 21 February 2016).

N: 1. keystone (n): “stone in the middle of an arch, which holds up the others,” 1630s, from key (n.1) in figurative sense of “that which holds together other parts” + stone. Figurative sense is from 1640s.
species (npl): late 14c. as a classification in logic, from Latin species “a particular sort, kind, or type” (opposed to genus), originally “a sight, look, view, appearance,” hence also “a spectacle; mental appearance, idea, notion; a look; a pretext; a resemblance; a show or display,” typically in passive senses; in Late Latin, “a special case;” related to specere “to look at, to see, behold,” from PIE *spek-. From 1550s as “appearance, outward form;” 1560s as “distinct class (of something) based on common characteristics.” Biological sense is from c. 1600. Endangered species first attested 1964.
2. Keystone species, keystone species of the kelp forest in ecology, a species that has a disproportionately large effect on the communities in which it occurs. Such species help to maintain local biodiversity within a community either by controlling populations of other species that would otherwise dominate the community or by providing critical resources for a wide range of species. The name keystone species, coined by American zoologist Robert T. Paine in 1969, was derived from the practice of using a wedge-shaped stone to support the top of an arch in a bridge or other construction.
3. Keystone species: Species who enrich ecosystem function in a unique and significant manner through their activities, and the effect is disproportionate to their numerical abundance. Their removal initiates changes in ecosystem structure and often loss of diversity.
4. Zoo biologists counter that those animals – which are often the most endangered – typically act as so-called keystone species, at the summit of a complex food web. By saving the keystone animal and its habitat, many smaller animals and plants are saved as well.

S: 1. OED – http://www.etymonline.com/index.php?term=keystone; http://www.etymonline.com/index.php?allowed_in_frame=0&search=species (last access: 21 February 2016). 2. EncBrit – http://global.britannica.com/science/keystone-species (last access: 21 February 2016). 3 & 4. TERMIUM PLUS – http://goo.gl/zbDhnH (last access: 21 February 2016).

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CR: biome, ecology, environment, sustainable development, umbrella species.