Foundation species

In ecology, the term foundation species is used to refer to a species that has a strong role in structuring a community. A foundation species can occupy any trophic level in a food web (i.e., they can be primary producers, herbivores or predators). The term was coined by Paul K. Dayton in 1972, who applied it to certain members of marine invertebrate and algae communities. It was clear from studies in several locations that there were a small handful of species whose activities had a disproportionate effect on the rest of the marine community and they were therefore key to the resilience of the community. Dayton’s view was that focusing on foundation species would allow for a simplified approach to more rapidly understand how a community as a whole would react to disturbances, such as pollution, instead of attempting the extremely difficult task of tracking the responses of all community members simultaneously. The term has since been applied to range of organisms in ecosystems around the world, in both aquatic and terrestrial environments. Aaron Ellison et al. introduced the term to terrestrial ecology by applying the term foundation species to tree species that define and structure certain forest ecosystems through their influences on associated organisms and modulation of ecosystem processes.

A study conducted at the McKenzie Flats at the Sevilleta National Wildlife Refuge in New Mexico, a semi-arid biome transition zone, observed the result of loss of a variety of different dominant and codominant foundation species of plants on the growth of other species. This transition zone consists of two Chihuahuan Desert species, black grama (Bouteloua eriopoda) and creosote bush (Larrea tridentata), and a Shortgrass Steppe species, blue grama (Bouteloua gracillis). Each species dominates an area with a specific soil environment. Black grama dominates sandy soils, while blue grama dominates in soils with high clay content, and creosote bush dominates fine-textured soil with surface gravel. This study noted that responses to the loss foundation species is dependent on a variety of different factors from the ability of a species to recover to the climate conditions of the ecosystem to the patterns in dominance and explored the possible reasons for the outcomes of the study. The results indicated that in areas with just one dominant foundation species, its loss caused a shift in dominance to a mixed dominant community. For example, the creosote bush dominated shrubland saw a shift in dominance to 32% by other shrubs, 26% by perennial grasses, and 22% by perennial forbs following the removal of creosote bush. Another finding was that regardless of the community type and the species removed, the loss of foundation species resulted in an overall increase in black grama supporting the notion that the outcome is greatly affected by recovery ability of species removed or loss.

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