Abstract: Niche partitioning is an ecological strategy that allows sympatric species, i.e., species that coexist in close proximity, to minimize direct competition by utilizing different resources. While this phenomenon is well-studied in a variety of organisms, terrestrial gastropods have been largely overlooked. In temperate regions of North America, more than 30 sympatric species of terrestrial gastropods can be found cohabiting in a small area of soil and leaf litter, but it remains unclear how so many species are able to coexist without extreme competition for resources. Carbon and nitrogen stable isotope analyses can provide further insight into this question by providing a semi-quantitative estimate of an organism’s diet.
This work investigates the diets of sympatric gastropod species from a range of temperate ecosystems in Ohio including a deciduous forest in East Fork State Park, a freshwater wetland in Cedar Bog Nature Preserve, and a coniferous forest in Hocking Hills State Park. Three to nine species of gastropods and all potential food resources, i.e., fresh vascular plants, leaf litter, moss, fungi, lichen, and soil organics, were isotopically analyzed and explored using the IsoSource linear mixing model. We tested the hypothesis that sympatric gastropod species in each ecosystem partition food resources to some degree to reduce competition.
Isotopic and model results suggest measured gastropods follow varied diets that include multiple food resources, but different species tend to partition resources in unique ways. Species inhabiting the coniferous forest and the freshwater wetland exhibited the least isotopic overlap, pointing to greater niche partitioning. In contrast, gastropods from the deciduous forest showed the most isotopic overlap, suggesting minimal niche partitioning between species. These results in part support our hypothesis and illustrate that sympatric species of terrestrial gastropods appear to partition food resources in their habitats, but the degree of niche partitioning may be more pronounced in some ecosystems than others. The reasons behind these patterns remain to be further explored in future research.
