Genetic Relationships among Invasive Hydrilla (Hydrilla verticillata L.f. Royle) Biotypes in the US and Their Implications for Management.

摘要

Hydrilla verticillata L.f. Royle (hydrilla; Hydrocharitaceae), an invasive submersed plant native to Southeast Asia and Australia, was first introduced into the US through the aquarium trade in Florida in the 1950s (Schmitz et al. 1991). Hydrilla impacts freshwater resources in the US by its aggressive, canopy-forming growth that degrades aquatic ecosystems, limits recreation, fouls boat motors, and clogs irrigation and hydroelectric plants. In the US there are two recognized hydrilla biotypes: the dioecious biotype is generally found in the southeastern and south central US; whereas the monoecious biotype is mostly found in the central Atlantic and northeastern US (Madeira et al. 2000). The dioecious biotype has been present, and spreading, in the US since the first introduction over 50 years ago. In contrast, monoecious hydrilla is widely recognized as a relatively recent introduction, first identified in the northeastern United States in 1982 (Steward et al. 1984). Since the initial identification, monoecious hydrilla has been reported in Connecticut, Massachusetts, Maine, New York, and as far south as Georgia and Alabama. Additional populations of the monoecious biotype are known to be found in Washington and California (Madeira et al. 2000). Management of hydrilla is typically accomplished through mechanical, chemical, and biological means. Mechanical harvesting of hydrilla has been attempted over the years but it is typically cost prohibitive and results in production of additional plant propagules through fragmentation. Chemical applications include complexed copper, diquat, endothall, fluridone, and more recently imazamox, penoxsulam, bispyribac-sodium, and flumioxazin (Gallagher and Haller 1990, Netherland 2009).