Invasive Species

When a new species is introduced into an ecosystem, there are four different interspecific interactions that can occur. These are interactions that occur between two different species living in the same community. These interactions could have positive, negative, or neutral effects on the involved organisms. One such interaction is predation. This is when one species, the predator, uses the other, the prey, for food. This interaction obviously benefits the predator, but not the prey. When an introduced species is a predator, it may become invasive if it can out-compete the native predators. This competition is the second interspecific interaction. This interaction hurts both species involved. When two species are both competing for the same resources, neither will be as successful as they would be alone. The last two possible interactions, commensalism and mutualism, would not make an introduced species invasive. Commensalism is when one species benefits and the other is unaffected, and mutualism is when both species benefit from the interaction. Most of the time, an introduced species cannot compete with native populations and does not survive. Of the species that do become successful in their new environment, the majority of these organisms have no effect on the ecosystem. For example, the pheasant is a bird that was introduced to North America from Asia. These birds have had no impact on native species. The species is considered invasive when it can out-compete and displace other species already present in the ecosystem.

An introduced species must exhibit certain characteristics in order to become invasive. For one, the organism must be able to reproduce in their new environment. They must also be able to out-compete the native populations. They must not be susceptible to herbivores or diseases, especially if these types of organisms characterize the ecosystem to which they have been introduced. Lastly, they must be able to survive in their new climate with the available resources.