Admixture and hybridization in North American cattails (Typha spp.)

每年都有成百上千的物种被无意或有意地转移到世界各地。大多数物种无法在它们被引入的新环境中生存。然而，由于一些尚不清楚的原因，一些引进的物种生存得非常好，成为入侵物种，主宰了新的栖息地，导致本地物种灭绝，并在根除计划上花费了数百万美元。导致生物入侵的引进不一定涉及特定地理区域的新物种：入侵也可以由引入本地物种的新遗传变种引起。如果一个物种的种群自然地出现在地理上分开的地区，比如加拿大的沿海省份和不列颠哥伦比亚省，这种情况就会发生。在这个例子中，一个单一物种的加拿大东部和西部种群已经彼此隔离了数千年，在此期间，它们进化成具有不同遗传谱系的东部和西部品种，尽管它们仍然被认为是一个单一物种的成员。如果来自不列颠哥伦比亚省的个体找到了通往沿海省份的路，它们可能会成为新栖息地的入侵物种。

Every year hundreds - possibly thousands - of species are either accidentally or intentionally moved around the world. Most species are unable to survive in the new environments to which they are introduced. However, for reasons that are not well understood, a few introduced species fare extraordinarily well and become invasive species that dominate new habitats, drive native species to extinction, and cost millions of dollars in eradication programs. Introductions that lead to biological invasions do not have to involve species that are new to a particular geographical area: invasions can also result from the introduction of new genetic varieties of a native species. This can happen if populations from a single species naturally occur in geographically separated areas, such as the Canadian maritime provinces and British Columbia. In this example, the eastern and western Canadian populations of a single species have been isolated from one another for thousands of years, during which time they evolved into eastern and western varieties with distinct genetic lineages, even though they are still considered members of a single species. If individuals from British Columia find their way to the maritime provinces, they could potentially become invasive in their new habitat.