The role of overseas genetic surveys to potentially accelerate biological control development for a new Hydrilla verticillata introduction in the USA

Documentation of fine-scale plant genetic identity in order to match weed genotypes between native and invasive ranges can be used to identify potential biological control agents from target genotypes in the hopes that they will be better adapted and thus more effective once introduced into the exotic range. However, the utility of this information for directing future exploration, for example upon introduction of a new weed genotype, is rarely considered. A cryptic introduction of the submersed aquatic weed, Hydrilla verticillata (L.f.) Royle (Alismatales: Hydrocharitaceae), was recently identified in the Connecticut River, which represents a new hydrilla haplotype not previously recorded in the USA. Because we have instituted concurrent plant genetic studies and biological control agent surveys during overseas exploration, potential herbivores of the cryptic introduction may already be known, requiring less resources if a biological control program of this haplotype is instigated. For the newly introduced haplotype and its closest relatives, we identified 22 herbivore taxa from China and Korea, including Bagous spp., Hydrellia spp., and a number of chironomids. This information may now be used to pursue agent development on the cryptic introduction without additional years and resources required to survey native hydrilla populations for new potential agents.