Understanding:
• 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
