The Role of Plant Systematics in Invasive Aquatic Plant Management

The correct identification of both invasive and native aquatic plants is crucial for effective aquatic plant management. Incorrect identification of the plants in our aquatic systems can lead to inadvertent outcomes such as eradicating native species or applying ineffective control strategies. While this practice may appear straightforward, the correct identification of invasive aquatic plant taxa has proven to be complex. Many aquatic plants are particularly difficult to identify correctly using morphology alone due to their often reduced floral characters and convergent vegetative morphology. The past two decades have given us the technological tools through molecular (DNA) sequence data and computational methods to more accurately identify nonnative plants in North America and have been particularly useful for early detection. Molecular tools have also revealed unique "genetic types" (i.e., genotypes), including newly formed hybrids among the most problematic of our invasive and wetland plants. Unique genotypes often correlate with different physical types that respond in unique ways to the environment around them. Given the body of literature describing variable responses of invasive taxa to their environment and well-documented herbicide resistant weed "biotypes", managers of invasive plants must discern the genetic identity to the finest relevant scale. We recommend: (1) creating a government-funded, centralized molecular lab for the purpose of quick and accurate aquatic plant identification, also referred to as DNA "barcoding" (this lab could immediately be used for early detection of invasive taxa with the intention of stopping invasive aquatic plants before they become a problem); (2) incorporating our growing knowledge of genotypes with studies of invasive taxa emphasizing ecological preferences, growth habits, reproductive ability, and herbicide and/or biocontrol resistance; and (3) integrating current internet sites that emphasize invasive aquatic plants into a single existing interactive site that will include not only known invasive plants, but all aquatic plant genera to facilitate early detection. Time and money can be used more effectively by aquatic plant management agencies if we develop reliable methods to correctly identify aquatic plant taxa before management is implemented.