Feeding habits of the exotic invasive slug Limax maximus: a basis for risk assessment of herbivory on forest and agricultural ecosystems

Abstract

Invasions of exotic herbivores often result in considerable damage to vegetation. Slugs are one of the herbivores that pose a high risk of altering vegetation when introduced to new sites. The large invasive slug, Limax maximus , was recently introduced into Japan. We examined its feeding behavior to assess potential effects on vegetation at introduced sites. We conducted two complementary experiments: feeding trials and DNA meta-barcoding analyses. In the feeding trials, we provided L. maximus with 23 test plants and calculated Acceptability Index (AI) values to evaluate palatability. Limax maximus clearly favored specific plants; average AI was highest for Brassica oleracea , followed by Lactuca indica, and Sambucus racemosa . DNA meta-barcoding analyses identified plants from six families in the feces of wild individuals. According to the generalized linear mixed model analyses, the plants that L. maximus preferred to eat were crops, herbaceous plants, and plants with glabrous leaves. Because native slugs and land snails do not show these preferences, L. maximus may exert herbivory pressure on native and agricultural plants that is different from that exerted by native molluscan communities. Our work demonstrated that combining multiple methods helps to estimate the potential risk of exotic herbivory in natural ecosystems. Additional research should examine