# A Regional DNA Barcode Library for Northern Rocky Mountain Arthropods to Support Biodiversity and Molecular Ecological Research

## TL;DR

The paper introduces a DNA barcode library for arthropods in the Northern Rocky Mountains, significantly increasing regional biodiversity data for ecological research.

## Contribution

The creation of the MPG Ranch Arthropod Library, a large-scale DNA barcode reference for arthropods in west-central Montana, filling critical gaps in regional biodiversity data.

## Key findings

- The MPG‐AL added 5154 Barcode Index Numbers (BINs) to BOLD, a 280% increase in Montana arthropod DNA barcode coverage.
- The library includes barcodes from 1793 species across 38 arthropod orders, with many taxa previously lacking reference sequences.

## Abstract

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.

We developed the MPG Ranch Arthropod Library (MPG‐AL), a COI DNA barcode reference library for arthropods of the Northern Rocky Mountains, to address gaps in barcode coverage for the western United States. From 86,533 specimens collected in Montana, we generated 52,270 DNA barcodes spanning 38 orders and 1793 species, adding 5154 Barcode Index Numbers (BINs) to BOLD—a 280% increase for Montana. The MPG‐AL establishes a strong foundation for regional biodiversity and molecular ecology research while highlighting the need for continued barcoding to fill remaining taxonomic gaps.