The structure of population genetic diversity in Vallisneriaamericana in the Chesapeake Bay: implications for restoration

Submersed aquatic macrophyte beds provide important ecosystem services, yet their distribution and extent has declined worldwide in aquatic ecosystems. Effective restoration of these habitats will require, among other factors, reintroduction of genetically diverse source material that can withstand short- and long-term environmental fluctuations in environmental conditions. We examined patterns of genetic diversity in Vallisneria americana because it is a cosmopolitan freshwater submersed aquatic macrophyte and is commonly used for restoring freshwater habitats. We sampled 26 naturally occurring populations of V. americana in the Chesapeake Bay estuary and its tributaries and found that the majority of populations have high genotypic diversity and are not highly inbred. Fourteen of the populations had high allelic and genotypic diversity and could serve as source sites for restoration material. However, substantial geographic structuring of genetic diversity suggests that caution should be used in moving propagules to locations distant from their source. In particular, we suggest that propagules at least be limited within four primary geographic areas that correspond to freshwater tidal and non-tidal, oligohaline, and seasonally mesohaline areas of the Chesapeake Bay.