Dietary Niche Partitioning Among Sympatric Terrestrial Gastropods in a Temperate Woodland

Abstract

Terrestrial gastropods are an integral part of the ecosystem because of their role in organic matter decomposition and the soil calcium cycle. While most species have traditionally been considered generalized herbivores, the specific dietary preferences of most taxa remain virtually unknown because gastropods’ behavior is difficult to observe in the wild due to their nocturnal habits and small body size. In forested areas across North America, upwards of 30 species can sometimes coexist within the same microhabitat, but it remains unclear if and how gastropods partition resources to minimize interspecific competition. This research investigated the diet of seven sympatric species of terrestrial gastropods from an Ohio temperate woodland using stable carbon and nitrogen isotope analyses. Results suggest that most species followed a varied diet that included variable proportions of vascular and non-vascular plants, fungi, lichen, and soil organic matter. Whereas some species (Anguispira alternata, Arion cf subfuscus, and Philomycidae sp.) showed more unique and specialized diets, others (Deroceras laeve, Euchemotrema fraternum, Mesodon thyroidus, and Ventridens ligera) were generalized feeders and overlapped in diet. These findings illustrate that terrestrial gastropod food webs are more complex than previously thought and support the hypothesis that some coexisting species reduce interspecific competition by partitioning resources.