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Introduction by Diffusion |
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Species can naturally spread after their introduction. Diffusion occurs when these exotic species cross artificial boarders such as those between states or countries. The building of channels, canals, and locks creates artificial connections between waterways, allowing the free movement of species across physical barriers. This has apparently been a factor in the spread of the zebra mussel (Dreissena polymorpha). It also facilitates the transport of species by vessels. On land, railways and highways provide similar routes of spread. Some of these introduced species could have been directly helped by humans at some point of their journey, but this may not always be the case. Are such species exotics in the new areas or not? Back to introduction of exotic species page or to the images of introduction page. |
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