Facilitators and outcomes of biological invasions by aquatic macrophytes

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Invasive species are non-native species that were introduced into a new geographical region and subsequently expanded their range while dominating new habitat. During this process, invasive species can displace native species, introduce pathogens to economically important species, alter ecosystem processes, and disrupt sites of human recreation. The numbers of invasive species have been steadily growing over the last few decades, and now they now comprise one of the biggest threats to ecosystems and biodiversity around the world. Furthermore, invasive species incur tremendous economic cost because they can decimate commercially important species, and collectively require extensive and costly management and prevention programs. ******Considerable research has addressed many aspects of biological invasions, but we still have a number of very important knowledge gaps that need to be filled. One example of this is our poor understanding of why some introduced (non-native) species become invasive, while others either go extinct or are maintained at very low levels with little to no impact on their surrounding habitat. A second knowledge gap surrounds the community effects of invasive species: although we know that the overall impact of invasive species is negative, we don't fully understand their effects on biodiversity across different spatial scales or their impacts on different types of habitat, e.g. whether they are most likely to invade habitat that has already deteriorated and is inadequate for many native species. These two aspects of biological invasions – the likelihood and the effects of invasions - are particularly understudied in aquatic systems. I propose using a combination of field, experimental and lab work to answer the following questions: 1) Do invasions of Ontario aquatic systems by non-native plants depend on a combination of environmental conditions plus the competitive ability of native plants, in other words are plants more likely to invade recently altered areas to which native species have not had time to adapt? and 2) To what extent do invasive plants alter aquatic ecosystems by reducing native biodiversity and leaving systems more susceptible to invasions by additional species? By filling in some of these critical knowledge gaps, my research will help managers to prevent biological invasions by prioritizing sites where prevention strategies should be focused, either because those sites are particularly vulnerable to invasions, or are particularly likely to experience extensive deleterious effects following invasions. Prevention is a far more successful strategy than the removal of established invasives, and my research will therefore provide substantial economic and social benefits to Canada.**