Invasive earthworms ingest and digest Garlic Mustard seeds at rates equal to native seeds.
The European and Asian earthworms introduced to eastern North American forests have great potential to facilitate plant invasions, in part through selective seed predation and dispersal. The invasive plant Alliaria petiolata (Garlic Mustard) contains secondary metabolites that may deter earthworms from eating its seeds. In 2 growth-chamber experiments, I determined whether the invasive earthworms Lumbricus terrestris (Nightcrawler) and Eisenia fetida (Red Wiggler) could aid the spread of Garlic Mustard by ingesting its seeds at lower rates than the similar-sized seeds of the native forest herb Geranium maculatum (Wild Geranium). Earthworms had similar rates of seed ingestion regardless of earthworm or plant species and digested the majority of seeds they ate (67-73%). There was no interaction between earthworm and plant species. Given a choice between Garlic Mustard and Wild Geranium, seed selectivity cannot explain positive associations between earthworm abundance and Garlic Mustard invasion.