Keystone Species | Ecology


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. 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, in 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. If a plant species was removed, there would
still be other plants for the birds to feed on. So the removal of a species would have little
overall effect on the community structure as a whole. Thank you for watching, if you found this
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