Environmental DNA: An Exciting New Frontier in Arthropod Monitoring and Conservation

At the halfway point of my 52-week journey sharing biodiversity research, I have observed numerous studies highlighting the power of environmental DNA (eDNA) in monitoring insects, with potential applications in agriculture, health, and conservation. It is an opportune time to discuss a recent systematic review which examines the current state and future potential of eDNA for monitoring and conserving terrestrial arthropods. Their work identifies key themes and trends in this field but also reveals concerning geographic and taxonomic biases—most eDNA studies favour species from temperate ecosystems, leaving tropical regions underexplored. Before delving deeper, here is a brief primer on eDNA.

Understanding eDNA

Environmental DNA (eDNA) refers to genetic material obtained from environmental samples—soil, water, or air—without directly sampling the organisms. This non-invasive method allows researchers to detect species presence and study biodiversity patterns without capturing or disturbing wildlife, addressing the “kill it to study it” ethical dilemma, especially for rare or endangered species, including arthropods. Since arthropods make up the majority of terrestrial animal biodiversity, eDNA could revolutionise large-scale monitoring.

The Rise of Arthropod eDNA Research

According to the review, eDNA studies on terrestrial arthropods have surged since 2015, accelerating after 2017. Most research focuses on insects, followed by arachnids, myriapods, and springtails. Within insects, orders with significant ecological or economic impacts—beetles, flies, butterflies/moths, and bees—are most studied.

Researchers have experimented with various environmental matrices to collect arthropod eDNA, including soil, plant material (leaves, flowers), water (from washing plants or traps), air, faecal material, and arthropod-produced substances like honey and spider webs. Each sample type can detect different arthropod communities, underscoring the importance of selecting appropriate sampling methods based on target species and habitat.

Advantages of eDNA in Arthropod Monitoring

The review highlights several key advantages of using eDNA techniques to study terrestrial arthropods:

• Non-invasive sampling: Detect species without capturing or harming them, which is crucial for rare or endangered arthropods.
• Efficiency: Potentially survey large areas more quickly and cost-effectively than traditional methods.
• Detection of cryptic species: Identify morphologically similar species that are difficult to distinguish visually.
• Early detection of invasive species: The sensitivity of eDNA allows faster identification of newly introduced pests.
• Biodiversity assessment: eDNA metabarcoding provides a broad overview of arthropod diversity in an ecosystem.

Challenges and Limitations of eDNA in Arthropod Monitoring

While promising, applying eDNA to terrestrial arthropod monitoring faces challenges:

• DNA degradation: In terrestrial settings, DNA may degrade quickly due to UV exposure and environmental conditions.
• Patchy distribution: Arthropod eDNA may be unevenly distributed, complicating representative sampling.
• Quantification issues: eDNA techniques are better at detecting presence/absence than estimating abundance accurately.
• Reference database gaps: Effectiveness relies on comprehensive genetic reference libraries, which are incomplete for many arthropod groups.
• Methodological standardisation: There is a need for standardised protocols in sampling, DNA extraction, and analysis to ensure comparability across studies.

Addressing Geographic and Taxonomic Biases

A significant finding from the review is the disparity in geographic and taxonomic coverage—most eDNA studies focus on temperate species, particularly insects beneficial or harmful to humans, like pollinators and pests. This bias limits our understanding of broader biodiversity and may obscure critical ecosystem interactions.

Bridging this gap requires global collaboration. Initiatives like BIOSCAN and BioAlpha illustrate how integrating knowledge from diverse regions can enhance understanding. Engaging scientists from biodiversity-rich but underrepresented areas ensures a comprehensive and equitable grasp of global biodiversity. Partnerships among taxonomists, ecologists, and geneticists can enrich eDNA databases, improving the accessibility and effectiveness of eDNA tools for conservation.

Future Directions: Towards Actionable Solutions

To advance the use of eDNA for terrestrial arthropod monitoring, the authors recommend:

• Expanding reference databases: Continue barcoding arthropod species, especially in understudied groups and regions, to improve eDNA identifications.
• Developing standardised protocols: Establish best practices for sample collection, processing, and analysis to enhance consistency and comparability.
• Conducting comparative studies: Compare eDNA results with traditional survey methods to validate eDNA effectiveness.
• Exploring multi-marker approaches: Use multiple genetic markers to improve species detection and identification accuracy.
• Investigating eDNA ecology: Better understand how arthropod eDNA persists and moves in terrestrial environments to optimise sampling.
• Addressing quantification challenges: Research methods to relate eDNA concentrations to species abundance.
• Integrating with other technologies: Combine eDNA with tools like automated image recognition or acoustic monitoring for comprehensive biodiversity assessments.

Applications in Conservation and Management

As eDNA techniques develop, they have the potential to significantly impact conservation and management practices:

• Biodiversity monitoring: Enable efficient, large-scale, long-term monitoring of arthropod communities to track changes and inform strategies.
• Pest management: Early detection of invasive or pest species through eDNA surveillance can improve response times and outcomes.
• Ecosystem health assessment: Arthropod eDNA profiles can indicate overall ecosystem health and function.
• Rare species conservation: Non-invasive eDNA sampling is valuable for monitoring endangered species without disturbance.

Conclusion: Embracing eDNA for a Sustainable Future

Environmental DNA offers a promising direction for conserving and understanding terrestrial arthropod biodiversity at a time when this knowledge is crucial. As we face rapid environmental changes and increased threats to biodiversity, employing efficient, ethical monitoring methods becomes imperative.

Global collaboration can catalyse significant advancements. By working together, we can capitalise on eDNA research, address its challenges, and develop effective conservation strategies for the arthropods that play essential roles in our ecosystems.

As we aim to unveil the vast hidden biodiversity beneath our feet, our approach must prioritise inclusivity, knowledge-sharing, and international collaboration for a sustainable future—for arthropods, ecosystems, and humanity.