Abstract
Leaf-litter-dwelling invertebrates serve an important role in ecosystem function by breaking down nutrients and potentially acting as indicators of habitat quality. However, this community is understudied due to difficulties related to sampling and taxonomic identification. To explore this community, we sampled leaf litter from the coastal and Cascade ranges of the Pacific Northwest of North America and searched > 200 samples for micro-invertebrates. We removed and photographed more than 400 invertebrate specimens, sequenced a portion of the mitochondrial gene cytochrome oxidase I (COI) for 60 samples, and used COI and the BLASTn database to identify invertebrates. Using these sequences and environmental data from the collection localities, we investigated the phylogeographic history of the two best-sampled species of micros- nails, the toothless column snail ( Columella edentula) and the conical spot snail ( Punctum randolphii). Results suggest that populations of these species from the coastal and Cascade ranges may have survived in a single refugium during the Pleistocene glacial cycles and recolonized the coastal and Cascade ranges during the Holocene. Our results add to the knowledge of species responses to the Pleistocene glacial cycles in the Pacific Northwest and suggest that future studies should aim to increase representation of micro-invertebrates, perhaps using metabarcoding techniques.