Genomic origins of insect sex chromosomes
Summary
Ingested 2026-04-21. 3 findings extracted and verified.
Findings worth citing
Finding 1 — Male heterogamety (XY/XO) is documented in 24 of 28 insect orders and encompasses 77% of sexually reproducing insect species investigated, making it the most common sex determination mode in insects.
Male heterogamety (XY, XO) is the most abundant form of sex determination in insects (Box 1), having been documented in 24 of 28 orders encompassing 77% of sexually reproducing species investigated. — p. 45
Why this is citable: This is a broadly-citable quantitative summary of the prevalence of male heterogamety across insects, useful as a background claim grounding arguments about ancestral states or the generality of XY systems.
Counter / limitation: The figure is drawn from the Tree of Sex database, which is biased toward well-studied taxa; undersampled orders (especially female-heterogametic and small orders) may shift these proportions, so treat as a coarse estimate rather than a precise prevalence.
Topics: sex_chromosome_evolution, karyotype_database
Finding 2 — In Drosophila miranda, the neo-Y formed by a Y-autosome fusion ~1–2 million years ago has already accumulated many transposable elements and pseudogenized or lost 40% of its ancestral autosomal genes.
In D. miranda the neo-Y, which formed by a Y to autosome fusion approximately 1–2 million years ago, has already accumulated a large number of transposable elements and 40% of the ancestral autosomal genes have been pseudogenized or lost — p. 46
Why this is citable: Provides a concrete rate-of-decay benchmark for young Y chromosomes, frequently cited to argue that Y degeneration is rapid and extensive early in its evolution.
Counter / limitation: Based on a single species (D. miranda); extrapolating this pace of decay to other insects or to older Y-chromosomes ignores lineage-specific effective population size, recombination, and selection differences.
Topics: sex_chromosome_evolution, y_naught_asymmetry
Finding 3 — The X chromosomes of Drosophila melanogaster and Anopheles gambiae share a region that is not homologous to the X of Tribolium castaneum or the Z of Bombyx mori; each is homologous to a unique autosome in the others.
the shared region of the D. melanogaster and Anopheles gambiae X is not homologous to the X of the beetle Tribolium castaneum or the Z of the silk moth Bombyx mori, but in each case the X (or Z) is homologous to a unique autosome in the other species — p. 48
Why this is citable: Key empirical synthesis showing that X-chromosome identity is not conserved across major insect orders, grounding claims about rapid sex chromosome turnover and the independent origins of insect sex chromosomes.
Counter / limitation: The cross-order homology inference rests on comparisons among only four reference genomes (Pease & Hahn 2012); denser sampling might reveal shared ancestral linkage groups currently obscured by limited taxon coverage.
Topics: sex_chromosome_evolution, genome_structure_evolution
Read the paper
doi.org/10.1016/j.cois.2014.12.003
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