Differences in field behavior between native gastropods and the fast-spreading invader Arion lusitanicus auct. non Mabille

Dispersal is a crucial process for population exchange and expansion, and traits that facilitate dispersal may be positively selected during biological invasions. Here, we performed a basic study on differences in behavior between the slug Arion lusitanicus auct. non MABILLE, 1868 (Gastropoda: Pulmonata), which is considered to be one of the 100 worst invasive species in Europe, and native gastropods. We assumed that the species is more active and less sensitive to otherwise aversive stimuli, and thus more likely to utilize novel environments. We quantified field densities and performed pitfall trap studies in 15 differently-structured habitats (urban, grassland, succession, riverine forest) in the floodplain of the LTER (Long Term Ecological Research) site ‘Rhine-Main-Observatory’ in Hesse, Germany. Here, A. lusitanicus was naturalized and scored 15 in terms of abundance rank, but was the dominant species in terms of trappability with the acidic Renner solution. A more detailed approach with a set of different baits showed that individuals of the invader were attracted to the acidic Renner solution, mustard oil, and garlic extract, all of which the native snails and slugs avoided. The results support the hypothesis that the invasive slug differs from other gastropods in its behavioral response to unusual, novel stimuli that may indicate some potential threat to other gastropod species. Future studies are needed to show if this behavior is related to personality traits such as exploration, boldness and risk-taking, and if it may have been positively selected in the context of the slug being passively spread in severely-transformed habitats such as gardens and greenhouses.