DNA barcoding has emerged as a key tool for biodiversity assessment under the Kunming-Montreal Global Biodiversity Framework. Critically examine the limitations of DNA barcoding revealed by recent research on haplodiploid insects.

Q. DNA barcoding has emerged as a key tool for biodiversity assessment under the Kunming-Montreal Global Biodiversity Framework. Critically examine the limitations of DNA barcoding revealed by recent research on haplodiploid insects. (15 marks, 250-350 words)

DNA barcoding identifies animal species from a 658 bp region of the mitochondrial COI gene, and underpins species-level monitoring for Target 3 (30×30) of the Kunming-Montreal Global Biodiversity Framework [1]. Recent research on haplodiploid insects shows the method is powerful but rests on an assumption of uniform molecular change that does not hold across taxa.

Strengths that justify its central role - Speed and scalability: barcode reference libraries now cover tens of thousands of species proxies (BINs) across 783 insect families and 26 orders, enabling assessment far faster than morphology-based taxonomy [2]. - Institutional uptake in India: the Centre for DNA Taxonomy of the Zoological Survey of India, with regional centres, generates barcodes of Indian fauna for national biodiversity documentation [3].

Limitations revealed by haplodiploid research - Rate is not uniform: in haplodiploid insects (Hymenoptera — ants, bees, wasps — where males arise from unfertilised eggs), amino acid substitution in COI is about 1.7× faster and the Ka/Ks ratio 3.5× higher than in diplodiploid lineages [2]. - Adaptive, not neutral, change: the elevated Ka/Ks signals positive selection driven by mito-nuclear co-evolution, since recessive nuclear mutations are fully exposed in haploid males — violating the near-neutral assumption behind fixed divergence thresholds [2]. - Distorted species counts: faster divergence can inflate cryptic species estimates in pollinator-rich Hymenoptera, while indels complicate alignment — risking misidentification of invasive or threatened taxa [2]. - Single-marker dependence: one maternally inherited gene cannot capture nuclear introgression or hybridisation.

Thus the critique is of calibration, not of the tool itself: barcoding remains indispensable, but its thresholds must be taxon-specific rather than universal. Recalibrating divergence cut-offs for haplodiploid orders, integrating nuclear markers, and strengthening ZSI's barcode libraries would make India's monitoring credible for its GBF commitments — ensuring that biodiversity accounting, a duty flowing from Article 48A, rests on sound science.

(~320 words)

Sources: 1. Kunming-Montreal Global Biodiversity Framework, CBD — 30×30 Target 3 and species-monitoring commitments 2. Pakrashi, Thompson & Hebert, "Haplodiploidy accelerates mitogenome evolution in insects", Proceedings of the Royal Society B 292(2059):20251813 — 658 bp COI barcode, 86,000+ BINs across 783 families and 26 orders, 1.7× substitution rate, 3.5× Ka/Ks, indels, positive-selection mechanism 3. Centre for DNA Taxonomy, Zoological Survey of India (MoEFCC) — India's institutional DNA barcoding of fauna