Multiple introductions of invasive Eurasian watermilfoil and recurrent hybridization with northern watermilfoil in North America

摘要

Aquatic plant managers and scientists have become increasingly interested in the potential for genetic variation to explain differences in the ecology or management response of invasive Eurasian watermilfoil. To date, genetic studies of invasive milfoil populations have focused on genetic identification techniques to distinguish Eurasian from hybrid watermilfoils. However, genetic variation within and among Eurasian and hybrid milfoil populations has been neglected, despite the potential for genetically distinct populations to exhibit unique ecological characteristics (including response to management efforts). Here we fill a gap in genetic studies of Eurasian and hybrid milfoils by employing amplified fragment length polymorphism markers (AFLPs) toassess patterns of genetic variation within and among Eurasian and hybrid watermilfoil. We demonstrate that Eurasian watermilfoil in North America consists of at least two distinct genetic lineages that were introduced to different parts of the continent on separate occasions. We also show that "hybrid watermilfoils" constitute a genetically diverse group that likely reflects a pattern of recurrent hybridization between native northern watermilfoil and both Eurasian lineages. The uncovering of geneticvariability in Eurasian and hybrid watermilfoils demonstrates a need for further study of these groups' ecology and management response. Finally, given the increasing interest in molecular identification methods, we compare identifications based on AFLPsto those of internal transcribed spacer (ITS) sequences. We found ITS identifications were commonly congruent with ITS, but a small fraction of ITS identifications incorrectly identified hybrid watermilfoils as Eurasian or northern milfoil.