Keystone Species


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•  Community structure can be strongly affected by keystone species

A keystone species is a species that has a disproportionately large impact on the environment relative to its abundance

  • It is analogous to a keystone in an arch – it fundamentally supports the whole structure and prevents it from collapsing

Keystone species may influence communities in a number of ways:

  • Predators – they can exert pressure on lower trophic levels to prevent them from monopolising certain resources
  • Mutualism – they can support the life cycle of a variety of species within a community (e.g. pollinators / seed dispersal)
  • Engineers – they can refashion the environment in a manner that promotes the survival of other species

There are numerous examples of keystone species within different communities:

  • Sea stars (predator) prey on urchins and mussels, preventing mussel overpopulation and coral reef destruction by urchins
  • Honey bees (mutualist) pollinate a wide variety of plant species, ensuring the continuation of the plant life cycle 
  • Beavers (engineer) build dams that transform the environment in a manner that allows certain other species to survive

Keystone species are not the dominant species (most numerous) within a community, nor do they have to be apex predators

Keystone Species

keystone species