A PCR-RFLP method to detect hybridization between the invasive Eurasian watermilfoil (Myriophyllum spicatum) and the native northern watermilfoil (Myriophyllum sibiricum), and its application in Ontario lakes

Abstract

The discovery of hybridization between the invasive Eurasian watermilfoil (Myriophyllum spicatum L.) and native northern watermilfoil (Myriophyllum sibiricum Kom.) has generated interest in establishing the hybrid’s distribution and invasiveness. Identification of hybrid M. spicatum × M. sibiricum requires molecular genetic analysis, however, as the hybrid’s morphology overlaps with both parent species. Using plants collected from 10 lakes in Ontario, Canada, we compared a previous method of identification (sequencing the nuclear ITS region) with a simpler screening method (PCR-RFLP of the ITS region). Both methods agreed on the identification of hybrid M. spicatum × M. sibiricum and both parent species, supporting the suitability of PCR-RFLP to screen for the hybrid. Four of 29 samples were identified as hybrid M. spicatum × M. sibiricum, which were all found in three adjacent lakes associated with the Rideau Canal Waterway. The PCR-RFLP method should enable greater sampling effort to screen for hybrid M. spicatum × M. sibiricum and establish its geographic distribution across connected waterways.