Abstract
Invasive species are a major concern in the current scenario of biodiversity loss. Most studies focus on vertebrates and insects, while other groups have been profoundly overlooked. Particularly, terrestrial slugs are among the most understudied taxa. Here, we contribute to expanding the scarce knowledge on exotic invertebrates by reporting the occurrence of two non-native terrestrial slugs in the Iberian Peninsula (northern Spain): Ambigolimax parvipenis, being also the first morphological confirmation for continental Spain, and Boettgerilla pallens, constituting the first record for continental Spain as well. Both species were collected in gardened urban areas or in peri-urban areas with a high presence of exotic ornamental plants. Some individuals were used for anatomical studies, while other ones were subjected to DNA extraction and PCR amplification and sequencing, comparing their sequences with closely related species from GenBank and confirming their previous morphological identification. Early detection of exotic species is crucial to avoid potential future threats. Unfortunately, many non-native species remain understudied or misidentified, leading to a silent invasion. Our findings entail a new step in the understanding of this neglected group and in the implications of urban gardened areas as a source of arrival of exotic fauna.