Invertebrate biodiversity and distribution on the invasive plant garlic mustard (Alliaria petiolata) and native plants in Vermont campgrounds

The population dynamics and spread of invasive plant species into new areas likely depend broadly upon their community ecology, including relationships with competing native plants and the associated suite of invertebrate pollinators, antagonists, and predators. Vermont campgrounds containing populations of the invasive plant garlic mustard (Alliaria petiolata), and native plants sweet cicely (Ozmorhiza sp.) and orange jewelweed (Impatiens capensis) were selected and surveyed for invertebrates in summers of 2011-2012. A. petiolata was compared with I. capensis in weekly surveys. A. petiolata was compared with Ozmorhiza sp. in bi-weekly surveys. Four randomly-selected 1 m² plots of each species within large (>15 m²) and small (<10 m²) patches were swept using 10 sweeps from an insect sweep net and collected specimens were returned to the laboratory for identification. Total invertebrate abundance, species richness (S), and Shannon-Weaver species diversity (H’) were compared between plant species and patch size across collection dates using factorial ANOVA with multiple comparisons. Overall, total invertebrate abundance was significantly higher on A. petiolata over Ozmorhiza sp. at Mt. Ascutney State Park, while species richness and diversity did not differ between the two plants. At Lake Carmi State Park, total invertebrate abundance, species richness, and species diversity were all significantly higher on I. capensis over A. petiolata. Results of this study suggest that the ability of A. petiolata to successfully outcompete native plants for space may be influenced by their relative associations with beneficial and antagonistic invertebrates.