Fungal endophytes increase biomass production in pale swallow-wort (Vincetoxicum rossicum (kleopow) barbar.)

Pale swallow-wort, Vincetoxicum rossicum (Kleopow) Barbar., is an invasive weed in the lower Great Lakes Basin of North America. We investigated the relationship between V. rossicum productivity and several environmental variables across 54 established V. rossicum populations in southern Ontario. Variables included climate measurements, soil characteristics (pH, texture, and nutrient status), habitat type, plant community, and the diversity of root-associated fungi. Vincetoxicum rossicum roots were collected at all 54 sites, and associated fungi were compared using terminal restriction fragment length polymorphism. Aboveground biomass of V. rossicum was measured at 23 sites with similar light regimes, allowing comparison between populations. Results suggested that abiotic soil variables, and habitat type have little effect on V. rossicum productivity. Aboveground biomass production was significantly correlated with precipitation, and the presence of fungal pathogens and dark septate endophytes. Annual precipitation and soil clay content were also positively correlated with the abundance of soil pathogens. Accumulation of these microbes may negatively affect co-occurring native plants and associated fungal partners. The presence of these fungal species in soil could be used as an indicator of site susceptibility to invasion by V. rossicum and assist in the development of management plans for this exotic vine.