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

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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. Recently introduced genetic lineages may explain why cattails (Typha latifolia, Typha angustifolia, and their hybrid Typha x glauca) are becoming increasingly aggressive wetland invaders. Cattails are large plants common to wetland habitats, and although they are native to North America, introduced European cattails have recently been identified in Canada and the USA. This means that North American cattails now comprise native and introduced genetic lineages, and the European lineages may be the cause of cattail invasions in North America. We will be looking at the extent to which European cattails - either on their own, or following interbreeding with North American cattails - are dominating Canadian wetlands. By using cattails as a model system, we will generate important information that can help managers to decide how important it will be in the future to monitor introductions of 'native' species through routes such as garden centres, because these 'native' species might actually represent non-native genetic lineages with the potential for invasive behaviour. Understanding the processes that drive biological invasions is a necessary precursor to the development of long-term management plans that aim to minimize future biological invasions.