Sex Determination, Sex Chromosomes, and Karyotype Evolution in Insects

Summary

Ingested 2026-04-21. 1 findings extracted and verified.

Findings worth citing

Finding 1 — Male heterogamety is the ancestral mode of sex determination in insects, with likelihood-based ancestral state reconstruction strongly supporting this state at the insect root.

We find strong evidence for the node leading to insects being male heterogametic (100% probability), but we have little power to distinguish between XY and XO sex chromosome systems (60% and 40% probability, respectively). — p. 5

Why this is citable: This is a core citable claim establishing the ancestral sex determination state for insects using a formal phylogenetic analysis across a >13,000 species database, grounding downstream claims about polarity of transitions.

Counter / limitation: The reconstruction cannot distinguish XY from XO ancestry and relies on order-level prior probabilities with simplifying assumptions (e.g., fixing HD loss rate to zero), so fine-scale transition inferences remain uncertain.

Topics: sex_chromosome_evolution, karyotype_evolution_overview

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