New DNA Sequencing Tool Reads Broken Genetic Clues to Name Species in Mixed and Degraded Samples

Forensic scientists and wildlife investigators now have a powerful new ally in the fight against species fraud and illegal animal trade. A research team led by scientists at Southern Medical University and Zhaoqing Medical College in Guangdong, China, has developed a mitochondrial DNA metabarcoding system based on targeted next-generation sequencing (tNGS) that can identify vertebrate species even when the DNA in a sample is fragmented, contaminated with multiple species, or heavily processed. The system, described in the International Journal of Legal Medicine, was designed from the ground up to meet the rigorous standards demanded by forensic practice, and its performance characteristics suggest it could become a workhorse tool in wildlife crime investigations, food authenticity testing, and biodiversity monitoring programs around the world.

The core challenge the researchers set out to solve is a familiar one to anyone working with trace biological evidence: DNA at crime scenes, in processed foods, or in seized wildlife products is rarely pristine. Heat, chemicals, time, and environmental exposure all shred the long DNA molecules that standard analytical methods depend on. Traditional DNA barcoding, which relies on amplifying a single gene region of several hundred base pairs, often fails outright when the template DNA is broken into pieces shorter than the target. The new assay sidesteps this limitation by targeting four mitochondrial genes simultaneously: cytochrome b (Cytb), cytochrome c oxidase subunit I (COI), 16S ribosomal RNA, and 12S ribosomal RNA. Because each of these markers can be amplified as short fragments, the probability that at least one usable stretch of DNA survives in a degraded sample rises dramatically.

Mitochondrial DNA is the molecule of choice for species identification for good reason. Each cell contains hundreds to thousands of mitochondrial copies compared with just two copies of any nuclear gene, which means mitochondrial targets are far more likely to yield amplifiable material from tiny or damaged samples. Moreover, the mitochondrial genome accumulates mutations at a rate that allows closely related species to be distinguished while remaining conserved enough that universal primers can bind across a wide range of vertebrate groups. By combining four independent markers in a single multiplex reaction, the new system builds redundancy into the analysis: if one marker fails to amplify or gives an ambiguous result, the other three can still deliver a species call.

The technical architecture of the assay follows the logic of targeted amplicon sequencing. Rather than sequencing entire mitochondrial genomes, which would be wasteful and impractical for degraded templates, the system uses carefully designed primer pairs to amplify short, informative regions of the four marker genes. These amplicons are then indexed with sample-specific barcodes, pooled, and sequenced in parallel on a next-generation sequencing platform. The resulting reads are processed through a bioinformatic pipeline that filters out sequencing errors and chimeric artifacts, clusters the sequences, and matches them against reference databases. This multiplex design means dozens of samples can be analyzed simultaneously, dramatically reducing both cost and turnaround time compared with running each marker separately.

What distinguishes this study from many previous metabarcoding efforts is the systematic forensic validation that accompanied the development. Following the recommendations of the International Society for Forensic Genetics (ISFG) for non-human DNA analysis, the team subjected the assay to a battery of performance tests covering the scenarios that matter most in real casework. Sensitivity testing revealed that just 10 picograms of genomic DNA from a single species—roughly the amount of DNA in a fraction of a single cell—was sufficient to detect at least one of the four markers for all species tested. When the input was raised to 100 picograms, reliable species identification was achieved using all four markers simultaneously. These thresholds place the assay firmly in the range needed for trace evidence analysis, where investigators often work with material scraped from a single bone fragment or a smudge on a knife blade.

Mixture analysis, a critical capability for food fraud detection and wildlife trafficking cases where products may contain multiple species, produced equally impressive results. In an equimolar mixture containing ten different species with a total DNA input of just one nanogram, the assay correctly identified all ten contributors. More striking still, the system detected minor components in binary mixtures down to a 99:1 ratio, meaning a species making up only one percent of the DNA in a sample could still be flagged. This level of sensitivity for minority contributors is exactly what is needed to catch adulteration, where expensive meat or seafood is diluted with cheaper substitutes at low percentages precisely to evade detection.

The degradation studies may be the most consequential for practical applications. The researchers deliberately fragmented DNA in experimental samples and then challenged the assay with the damaged templates, alongside DNA extracted from highly processed food matrices such as cooked and commercially prepared meat products. In both scenarios, the four-marker system recovered enough sequence information to make species assignments, demonstrating that the short amplicon strategy performs as intended under the harshest conditions forensic analysts are likely to encounter. Processed foods represent one of the most common contexts for species fraud, and the ability to identify constituents in cooked, canned, or otherwise transformed products closes a significant gap in food authentication testing.

Validation extended beyond the laboratory to genuine casework samples, where the tNGS-based multiplex assay demonstrated broad-spectrum vertebrate identification across real-world evidence. The authors report that these case studies confirmed the practical value of the system for three major application areas: curbing wildlife trafficking, mitigating food fraud, and facilitating biodiversity monitoring. In wildlife trafficking investigations, the ability to identify species from seized products—whether carved ivory, dried meat, traditional medicine ingredients, or leather goods—provides prosecutors with the species-level evidence needed to establish that a crime against protected fauna occurred. For food regulators, the assay offers a screening tool capable of auditing supply chains for substitution and mislabeling. For ecologists, the same chemistry can be applied to environmental DNA samples to survey vertebrate diversity in a given habitat without needing to observe or capture animals directly.

The development team, which included collaborators from the Guangzhou Public Security Bureau, the Nanchang Police Dog Base of the Ministry of Public Security, Jinan University, and the Anti-Drug Technology Center of Guangdong Province, emphasized adherence to ethical research standards throughout the study. Animal specimens were provided by the Guangzhou Zoo and the Guangzhou Wildlife Research Center with approval from the Animal Ethics Committee of those institutions. The work was funded in part by the National Natural Science Foundation of China and the Jiangxi Provincial Key Research and Development Program, reflecting the strategic priority that Chinese research agencies have placed on forensic multi-omics and wildlife protection technology.

Looking ahead, the convergence of targeted sequencing, multiplex mitochondrial barcoding, and rigorous forensic validation points toward a future where species identification becomes as routine and standardized as human DNA profiling is today. The reference sequences used in the assay are publicly accessible through the National Center for Biotechnology Information database, and the authors have made raw data available with the publication, supporting transparency and reproducibility. As sequencing costs continue to fall and reference databases expand, systems like this one could be deployed in customs laboratories, food inspection agencies, and conservation field stations worldwide. For investigators racing to document the scale of illegal wildlife trade—a market estimated to be worth billions of dollars annually—and for consumers who deserve to know what is actually in their food, a tool that can name a species from a fragment of damaged DNA may prove to be one of the most consequential forensic innovations of the decade.

Subject of Research: A mitochondrial DNA metabarcoding system based on targeted next-generation sequencing for forensic identification of vertebrate species in degraded and mixed DNA samples

Article Title: A mitochondrial DNA metabarcoding system based on tNGS enables multiplex identification of vertebrate species in samples containing degraded and mixed DNA

Article References: Liu, X., Su, C., Wei, R., Chen, X., Le, J., Xiao, G., Chang, J., Liang, S., Wu, X., Liu, C., Liu, H., Du, W., Liu, C., & Chen, L. (2026). A mitochondrial DNA metabarcoding system based on tNGS enables multiplex identification of vertebrate species in samples containing degraded and mixed DNA. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-04024-4

Image Credits: AI Generated

DOI: 10.1007/s00414-026-04024-4

Keywords: DNA metabarcoding, targeted next-generation sequencing, mitochondrial DNA, forensic science, wildlife trafficking, food fraud, species identification, degraded DNA, cytochrome b, COI, biodiversity monitoring, vertebrate species