Do fungal mutualists alter dominance and invasibility of dune plant communities?

Mutualisms have received relatively little attention in the study of species invasions, despite their recognized importance in many ecosystems.  In our research, we assess how two mutualists, endophytic fungi (EF) and arbuscular mycorrhizal fungi (AMF) affect invasion of Great Lakes sand dune plant communities dominated by the native beach grass Ammophila breviligulata.  Because sand dunes are subject to blow-outs, mining efforts, and other disturbances, restoration of dunes by planting Ammophila has become a common practice.  We recently discovered that a common nursery variety of Ammophila (Cape) sold in Michigan is almost 100% infected by EF, while native Michigan populations have much lower frequencies of infection. A greenhouse experiment showed that the Cape variety of Ammophila is more competitive and more resistant to herbivory than native Michigan plants.  A pilot survey of dune communities indicated that AMF species composition of natural dunes differed from that of restored dunes.  To further address the relationship between plant diversity, EF infection, and AMF diversity, we surveyed 18 paired natural and planted populations of Ammophila in Indiana and Michigan during the summer of 2006.  Though most populations in the survey showed no evidence of EF infection, restored sites did have lower plant species richness than natural sites.  Future work will involve a restoration experiment, with results from this project providing insight for future dune restoration efforts.