A Regional DNA Barcode Library for Northern Rocky Mountain Arthropods to Support Biodiversity and Molecular...

Arthropod DNA barcode reference libraries have advanced ecological research but remain incomplete in many areas, including the western United States. To improve coverage in the Northern Rocky Mountains, we developed the MPG Ranch Arthropod Library (MPG-AL), a cytochrome oxidase I (COI) DNA barcode reference library for local arthropods in west-central Montana. From 2017 to 2019, we collected 86,533 specimens from various habitats, generating 52,270 DNA barcodes for arthropod taxa from 38 orders, 389 families, 1668 genera, and 1793 species. A comparison of the MPG-AL taxonomic coverage with a combined dataset of publicly accessible Montana arthropod DNA barcodes in the Barcode of Life Database (BOLD) and Montana Natural Heritage Program occurrence records revealed that the MPG-AL added references representing 5154 Barcode Index Numbers (BINs) to BOLD. These additions mark a 280% increase for Montana arthropod DNA barcodes, including 1140 new BINs for taxa previously lacking reference barcode sequences in BOLD. The MPG-AL provides a substantial foundation for establishing a comprehensive arthropod DNA barcode database in the Northern Rocky Mountain ecoregion. However, many taxa still lack reference barcode sequences, particularly in large, diverse insect orders. Future barcoding efforts are encouraged to expand regional taxonomic coverage through targeted sampling and collaborations with regional entomological collections. A comprehensive regional arthropod DNA barcode library will enhance our understanding of arthropod population trends and trophic relationships in the western United States amid persistent threats such as climate change, habitat loss, pesticides, and invasive species.