| Invasive species apparently compete with native species by increasing abundance or altering behavior of native consumers, and causing increased granivory or herbivory on native species. Coastal dune communities in Humboldt County, California are heavily invaded by European Beachgrass (Ammophila arenaria) and yellow-bush lupine (Lupinus arboreus), and experienced consequent major changes in composition despite efforts to control these exotics. We tested whether these invaders apparently compete with two native plants, silky beach pea (Lathyrus littoralis) and yellow sand verbena (Abronia latifolia), using seed addition plots in dune areas alternately dominated by a native plant assemblage, lupine, and beachgrass. We excluded rodents from beach pea and sand verbena plots matched with a paired control across these three plant community types; if beachgrass and lupine apparently compete with beach pea sand verbena, we expected greater effects of rodent exclusion on germination and seed removal in invaded areas. Rodent exclusion decreased seed predation and increased germination similarly across all three community types for beach pea, but not for sand verbena (few sand verbena germinated, limiting our inference for this species). Thus, granivory may limit recruitment of native plants, especially beach pea, yet we did not detect clear evidence of apparent competition with invaders. |