Ecology: Invasive Species

An ecosystem is all of the biotic and abiotic factors in a community. Biotic factors are the living things and abiotic factors are the nonliving things. A community is where many different species live together. Biotic factors include every species of animal, plant, bacteria, protest, and fungi in the community. Abiotic factors include the soil, water, and the weather. The living species have many different relationships with each other that keep the ecosystem running. In the ocean the whale eats a seal: a predator/prey relationship. On land the tick sucks blood from a dog: a parasitic relationship. A bee pollinates a flower and gets a meal: a mutualistic relationship. A clown fish hides in the stinging tentacles a sea anemone and gains its protection but gives nothing back: a commensalistic relationship. All of these relationships are how species interact with each other. In an ecosystem the relationships between organisms is very important and when factors are introduced to the ecosystem to change these relationships there are often problems.

A species’ niche is what a species does in an ecosystem. What it eats, what eats it where it lives, and when it is active. No two species can share exactly the same niche, but often they can overlap. The warbler birds each feed on different insects, but in the same tree. The niches are almost identical except that they feed in different parts of a tree. If the different species of warbler did share exactly the same niche there would be competition for resources and either the niche would be split or one species would die out.

When an alien species comes into an ecosystem and starts competing with the native species for a particular niche, it is called an invasive species. When a species invades it throws off the balance of the ecosystem. If it fills a niche that has not been filled yet then it could possibly make a new home for itself in this new ecosystem. More often the case is that the invasive species invades a niche that is already taken by a native species.

In the case of the New England Cottontail its niche is being invaded by the Eastern cottontail. The two species seem to share the exact same niche. The rabbits realized niche includes being food for wolves, and eating the underbrush so it does not grow too much. It seems that the Eastern Cottontail does the same thing but it spends more of its time in fields and the New England Cottontail spends more time in the woods. The Eastern Cottontail is more aggressive and is pushing out the NE Cottontail. This could cause a problem because the Eastern Cottontail does not eat the underbrush as much as the NE Cottontail, and this could cause a problem for the forests. The Eastern Cottontail also carries a disease that can be transmitted to humans through tick bites. The Eastern Cottontails were brought to New England in the 1930’s because it was believed they were easier to stalk. Now the NE Cottontails are in danger of extinction because of human involvement.

Ecosystems are very fragile and if aspects of the ecosystem are changed even in the most minimum way the whole ecosystem could suffer. Invasive species usually invade because of human involvement. It is not always on purpose, and because of the amount of travel done in the world today more invasive species are getting put into ecosystems. The boats and airplanes have basically made the world into one continent. This means that not as much diversity is able to exist in the world and the number of species in the world is decreasing. Less biodiversity in the world is dangerous because if there is only one species of fish for example and a disease starts killing the fish then every fish in the world will die of this illness because there is only one species. More biodiversity means a healthier ecosystem.

Lake Victoria in Africa evolved independent of outside factors and species formed there that could not be found anywhere else in the world. Fisherman brought the Nile Perch, a large fish, into Lake Victoria because it was big and easy to fish for. The Perch ended up eating all the other fish in the pond. The unique species of Lake Victoria where destroyed. The Perch didn’t only destroy the native species of fish it also increased the amount of fisherman. The increased amount of fisherman led to more crocodile attacks. The Water Hyacinth is also an invasive species in Lake Victoria. A man brought his girlfriend a Water Hyacinth over from France and somehow it escaped and spread into the Lake. The Hyacinth took over Lake Victoria making it difficult for the fishing boats to get out into the Lake to fish. The Hyacinth also poisons the water and schistosomiasis is spreading to the humans. An African Scientist found a cure for the invasive hyacinth by introducing its natural enemy weevles. Before introducing the weevles to Lake Victoria, the scientist made sure the weevles did not eat any of the other natural plants.