Comparative ecological niche models predict the invasive spread of variable-leaf milfoil (Myriophyllumheterophyllum) and its potential impact on closely related native species
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- Thum, R.A. & Lennon, J.T. Biol Invasions (2010) 12: 133. doi:10.1007/s10530-009-9437-0
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Invasive species can alter patterns of biodiversity by displacing closely related native species that occupy similar habitats. We used multivariate ecological niche modeling to determine the potential spread and displacement of native congeners by the invasive aquatic plant, variable-leaf milfoil (VLM, Myriophyllum heterophyllum) in New Hampshire, USA. We show that VLM occurs almost exclusively in “higher order” lakes characterized as large, low elevation systems with relatively high pH, alkalinity and conductivity. In contrast, native milfoils occur across a broad range of lake orders. The strong association between lake order and VLM invasions suggests that VLM is most likely to displace native milfoils in higher order lakes. However, the mechanism by which VLM occurs in higher order lakes—higher propagule pressure versus higher growth and survivorship—is unclear. We therefore caution that native species may ultimately be susceptible to displacement from lower order lakes if the current distribution of VLM reflects higher propagule pressures. Our model provides a valuable tool for the prioritization of monitoring efforts.