Purple loosestrife populations have developed into a highly aggressive and invasive weed in several Northern states (MN, NY, NJ etc.). How these populations arose is a key question in developing control strategies. Therefore, we initiated a study to elucidate the origin and genetic structure of invasive populations using isozyme analysis. The germplasm examined included invasive populations found in MN, NY, NJ, WI and MD, populations of Lythrum alatum, populations of L. virgatum and 22 cultivars of L. salicaria, the suspected progenitor of the invasive populations.
Unique isozyme patterns for most cultivars was observed and these were consistently indicative of that clone over repeated sampling. Clones of putative “salicaria” origin could not be distinguish from those of putative “virgatum” origin.Significant isozyme polymorphism was observed within and among the 26 Lythrum populations. Indicating that isozymes can be an important tool in studies on the structure and evolution of invasive loosestrife populations.
To date, our isozyme analysis indicates that L. salicaria and L. virgatum are not distinct species. It appears that the decision by the MN Department of Agriculture to add all horticultural lines to the noxious weeds list regardless of origin was a prudent decision.
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