Do pseudogenes pose a problem for metabarcoding marine animal communities?
Bibliographic record
Abstract
Because DNA metabarcoding typically employs sequence diversity among mitochondrial amplicons to estimate species composition, nuclear mitochondrial pseudogenes (NUMTs) can inflate diversity. This study quantifies the incidence and attributes of NUMTs derived from the 658-bp barcode region of cytochrome c oxidase I (COI) in 156 marine animal genomes. NUMTs were examined to ascertain if they could be recognized by their possession of indels or stop codons. In total, 309 NUMTs ≥150 bp were detected, with an average of 1.98 per species (range = 0-33) and a mean length of 391 ± 200 bp. Among this total, 75 (24.3%) lacked indels or stop codons. NUMTs appear to pose the greatest interpretational risk when short (<313 bp) amplicons are used, such as in environmental DNA studies, dietary analyses or processed fish identification. Employing the standard amplicon length (313 bp) for marine metabarcoding, NUMTs could potentially inflate the operational taxonomic unit (OTU) count by 21% above the true species count while also raising intraspecific variation at COI by 15%. However, when both amplicon length and position are considered, inflation in OTU counts and in barcode variation were just 9% and 10%, respectively, suggesting NUMTs will not seriously distort biodiversity assessments. There was a weak positive correlation between genome size and NUMT count but no variation among phyla or trophic groups. Until bioinformatic advances improve NUMT detection, the best defence involves targeting long amplicons and developing reference databases that include both mitochondrial sequences and their NUMT derivatives.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.004 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".