Genetic diversity and ecological success of the invasive riparian plant Mimulus guttatus

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The study of biological invasions can help us to design effective strategies to prevent, and manage invasive species. Habitats associated with rivers and streams are particularly susceptible to biological invasion, both because of their natural levels of disturbance and because they are often subject of considerable man-made modification. Networks of river and streams facilitate the dispersal of invasive species which can potentiate their negative effects and make their control a challenging task. In fact, some of the most prominent invasive plant species in the UK occur in close association with water bodies (e.g. Himalayan balsam, giant hogweed, Japanese knotweed). Despite a long history of studying biological invasions in the UK, large gaps of knowledge exist in the structure of genetic variation of invasive riparian species. The distribution of genetic variation both within and between populations holds a trove of information regarding the history of introduction and spread of invasive species, the extent of genetic connectivity among them, and ultimately the potential of invasive species to keep adapting to novel environments and advance their spread under changing environmental conditions. Elucidating these biological patterns is the necessary first step towards designing lasting and successful strategies to deal with biological invasions.Our study focuses on yellow monkey flowers (Mimulus guttatus), a widespread invasive plant that is mostly restricted to permanent and temporary bodies of running-water. It propagates both sexually via seeds and asexually through plant fragments carried by water. Monkey flowers were introduced to the UK from North America in the early 1800's, and are currently found throughout the British Isles. Monkey flowers are excellently suited for studying genetic and evolutionary processes during invasions. The ecology and evolution of monkey flowers has been extensively studied in its native range during the past 50 years, where it has become a model for studies of local adaptation, population structure, reproductive strategies, speciation, and genomics. No other UK invasive riparian plant has similar resources readily available, making M. guttatus the obvious choice for studying the ecological genetics of invasive species.Here we will investigate the spatial genetic structure on an invasive riparian plant from broad geographic scales to small, within-population levels. In the first component of the work we will sample 40 populations of monkey flowers across the UK at different spatial scales from broad geographic regions to multiple populations within water catchments. The data generated in this component will allow us to determine the general genetic structure of monkey flowers in Britain, to test competing hypothesis of the pattern of colonization and spread of this species here, and to measure genetic connectivity across spatial scales. In the second component of the work we will sample at the fine spatial scale to estimate the rates of sexual and asexual reproduction, which is a fundamental determinant of the dynamics of invasive species. These data will allow us to calculate for the first time, the importance of asexual propagation to the structure of genetic variation and its relationship with ecological success in invasive monkey flowers. By combining genetic analyses with measurements of ecological success, we will infer historical patterns of invasion and connectivity between populations, and reveal whether the mode of reproduction correlates both with overall genetic diversity and ecological success.Our project provides an exceptional opportunity to establish monkey flowers as a model for the study of biological invasions in the UK. This leading project will set the stage for future work on the ecology, evolution and management of invasive species in the UK and elsewhere.