ASSESSING NICHE PARTITIONING AMONG INTRODUCED AND NATIVE SLUGS USING STABLE ISOTOPE ECOLOGY

Ecological theory postulates that different species of animals cannot use the same resources and coexist in the same ecological niche. Interspecific competition between sympatric taxa could either lead to the extinction of the weakest competitor; or alternatively, species would partition resources to minimize competitive exclusion and cohabitate in harmony. While this hypothesis has been repeatedly tested across many major animal groups, primarily among vertebrates, little is known if and how sympatric terrestrial gastropods compete or divide resources in the same microhabitat. This study investigates whether the introduced (Arion subfusucs) and native (Deroceras laeve) species of slugs from East Fork Lake Park, a temperate woodland located 27 miles east of Cincinnati, compete for the same foods. To achieve this goal, we used stable isotope ecology, an effective approach commonly applied to many other animals, but never used in slugs thus far. Stable carbon (𝛿¹³C) and nitrogen (𝛿¹⁵N) isotopes of slugs’ body tissues and surrounding food resources (i.e., vascular plants, moss, fungi, lichen, soil organics, etc.) were analyzed, and the resulting isotope data was then modeled using the IsoSource software to semiquantify the slugs’ diet. Preliminary results reveal that the introduced and native species of slugs exhibit significantly different isotopic values with minimal overlap, suggesting that they appear to follow slightly different diets. The model’s results indicate that while the native species consumes a more varied diet, the introduced species primarily relies on moss. This apparent dietary difference between species suggests that slugs may be partitioning the resources to minimize competition. Ongoing and future research investigates other native and invasive species of slugs and their diet to assess if this finding is an anecdotal situation or a common phenomenon among slug communities in this forest.