Meeting Abstract
Invasion of ecosystems by exotic plants is considered to be one of the main threats to biodiversity globally. According to the enemy release hypothesis, plants which are introduced to a non-native environment often escape their coevolved predators and become very abundant. In Maryland, many invasive plant species are native to the Japanese archipelago. However, two Japanese herbivores (sika deer Cervus nippon and Japanese beetles Popillia japonica) have also been introduced to Maryland and are now classified as invasive. In this case, the invasive plants may not have escaped their coevolved predators. Sika deer and Japanese beetles have the choice between coevolved plants which are also native to the Japanese archipelago or novel plant species which are native to Maryland. We conducted cafeteria-style preference tests to determine the dietary preference of these herbivores. Sika deer showed significant preference for novel plant species in the field. Japanese beetles tended to colonize coevolved plant species in the field, but showed no significant dietary preference in lab assays. Differences in dietary preferences of the herbivore species are possibly due to the different scales of these grazers and their scope for adaptation. Sika deer have greater mobility than beetles, permitting them to be more selective in their dietary choices. Beetles, on the other hand, have much shorter generation times and can potentially adapt faster to new chemical defenses, allowing them to graze on both coevolved and novel plant species. Further chemical and morphological trait analyses of plant species used in our study are required to reveal other factors driving herbivore dietary preference in a non-native world.
