Rhamnus cathartica alters seed predation of native and exotic species
Rhamnus cathartica (Rhamnaceae) is a shrub or small tree species which was originally introduced into North America in the 1800s as an ornamental hedge plant. The species is native to Europe, and North and West Asia. Since its introduction into the US, the species has become an invasive alien plant in a number of States and is a prohibited species in New Hampshire, a restricted noxious weed in Iowa and a primary noxious weed in Minnesota. In the present study, which was conducted in a 485 ha reserve in Wisconsin (US), dominated by deciduous trees with a 50 -100 % cover of R. cathartica in the understory, 16, 20 x 20 m plots were randomly selected. In eight of these plots R. cathartica was removed but before and after removal light measurements were taken in each plot. Seed predation was measured for R. cathartica and four native species Acer rubrum, A. saccharum, Prunus serotina and Quercus rubra in each plot over two years. At each plot small mammal activity was evaluated. The removal of R. cathartica led to increased light levels, increased leaf litter depth and lower small mammal captures. Seed removal was reduced in cleared plots for A. rubrum and A. saccharum indicating that the presence of R. cathartica can lead to indirect competition for native species by increasing seed predation in invaded areas.
Bartowitz KJ, Orrock JL (2016) Invasive exotic shrub (Rhamnus cathartica) alters the timing and magnitude of post-dispersal seed predation of native and exotic species. Journal of Vegetation Science 27, 789-799.