The rate of mitochondrial genome evolution in insects has been found to be linked to their sex-determination system. Explain the mechanism proposed and discuss its implications for biodiversity monitoring in India.

Q. The rate of mitochondrial genome evolution in insects has been found to be linked to their sex-determination system. Explain the mechanism proposed and discuss its implications for biodiversity monitoring in India. (15 marks, 250-350 words)

The mitochondrial COI gene — the universal DNA barcode for animals — was long assumed to evolve at rates set by mutation, metabolism and population size. A 2025 study in Proceedings of the Royal Society B adds an unexpected driver: the insect's sex-determination system [1].

The proposed mechanism - Haplodiploidy (arrhenotoky): females are diploid (fertilised eggs), males haploid (unfertilised eggs) — seen in Hymenoptera (ants, bees, wasps), some thrips and bark beetles; most insects are diplodiploid [1]. - Mitochondrial proteins of the oxidative phosphorylation complexes must function alongside nuclear-encoded subunits, requiring continuous mito-nuclear co-evolution. - In haploid males there is no second allele to mask recessive nuclear mutations, so selection acts on them fully — allowing co-adapted mito-nuclear combinations to be fixed faster [1]. - Evidence across >86,000 BINs, 783 families, 26 orders: amino-acid substitution 1.7× higher and Ka/Ks 3.5× higher in haplodiploids — the signature of positive selection, not merely elevated mutation or drift [1].

Implications for biodiversity monitoring in India - Threshold recalibration: uniform barcode-divergence cut-offs may over-split haplodiploid taxa, inflating cryptic-species counts; clade-specific thresholds become necessary. - Institutional stake: the Zoological Survey of India, custodian of the National Zoological Collection and a Designated Repository under the Biological Diversity Act, 2002, generates thousands of barcodes annually and would need to revise reference-library annotation [2]. - Pollinator conservation: bees, being Hymenoptera, fall in the affected group — reliable identification underpins apiculture and pollinator-decline monitoring under India's updated NBSAP (2024) [3]. - Biosecurity: misidentification of invasive thrips or parasitoid wasps at quarantine points carries agricultural risk. - Global commitments: species-level accuracy is foundational to the Kunming-Montreal Framework's 30×30 target, to which India's 23 national targets are aligned [3][4].

Thus a finding in evolutionary genetics translates directly into methodological correction for conservation science. India should invest in taxon-calibrated barcoding standards and expand indigenous reference libraries, so that molecular monitoring genuinely advances the NBSAP's goal of halting biodiversity loss by 2030.

(~330 words)

Sources: 1. Pakrashi, Thompson & Hebert, "Haplodiploidy accelerates mitogenome evolution in insects", Proceedings of the Royal Society B, 2025 — haplodiploidy definition, mito-nuclear mechanism, 86,000 BINs, 1.7× and 3.5× figures 2. Zoological Survey of India, Annual Report 2024–25 — ZSI barcoding programme and Designated National Repository status 3. PIB, "India launches updated National Biodiversity Strategy and Action Plan at CBD COP-16" (2024) — updated NBSAP and 23 national biodiversity targets 4. CBD, Kunming-Montreal Global Biodiversity Framework — 2030 Targets — Target 3 (30×30) and species-monitoring requirement