In this video we are going to discuss the concept of a keystone species. A keystone species is a plant or animal species that plays an important role in the structure and maintenance of an ecological community. This keystone species affects not only the other species in the community but the functioning of the community.
Predatory species as keystone species occur when the predator predates on another predator or consumer down the food chain, and doing so helps reduce its predation on many species below it, keeping the community in balance. These are called top-down communities. An example of a predatory keystone species is seen between the keystone species the sea otter and their predation of the kelp-consuming sea urchins.
Sea urchins feed heavily on sea kelp, the sea kelp providing a habitat for a diverse range of other species. Their predation on the sea urchins keeps this community in balance. If the keystone species, the sea otters, were removed, the population of sea urchins would increase, and in turn consume too much kelp, affecting the other species living and feeding on the kelp. Keystone species are also observed in species that have mutualistic relationships. An example of mutualistic keystone species is seen between the frugivorous bird the cassowary and the many plants that are reliant on them for seed germination and dispersal.
The relationship in the community between frugivore and fruiting tree are mutualistic. the frugivore gets food and the plant gets dispersal and often germination from the frugivore. If the cassowary was removed from a community, these plants that are reliant on them would no longer be able to propagate within this community.
There would be no regrowth of these plants and the species composition in the community would change due to this keystone species being removed. If we now compare this example to non-keystone species in a community. There would be several more generalist, frugivorous birds who feed on the fruits of several generalist trees. No specific single species of bird or plant is reliant on a specific species of plant or bird.
If you removed a bird species, there would still be other birds able to germinate the plants. So the removal of a species would have little overall effect on the community structure as a whole. Thank you for watching.
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