Escalation by duplication: Milkweed bug trumps Monarch but

What this paper is about

Monarchs resist milkweed toxins through changes to the catalytic subunit of their sodium-potassium pump. The large milkweed bug, feeding on the same plants, has gone further: it has duplicated the gene and modified the copies.

The title is a comparison. The bug's solution is the more elaborate of the two.

Summarised here from the abstract below. Not the authors’ words.

Abstract

The iconic Monarch butterfly is probably the best-known example of chemical defence against predation, as pictures of vomiting naive blue jays in countless textbooks vividly illustrate. Larvae of the butterfly take up toxic cardiac glycosides from their milkweed hostplants and carry them over to the adult stage. These compounds (cardiotonic steroids, including cardenolides and bufadienolides) inhibit the animal transmembrane sodium-potassium ATPase (Na,K-ATPase), but the Monarch enzyme resists this inhibition thanks to amino acid substitutions in its catalytic alpha-subunit. Some birds also have substitutions and can feast on cardiac glycoside-sequestering insects with impunity. A flurry of recent work has shown how the alpha-subunit gene has been duplicated multiple times in separate insect lineages specializing in cardiac glycoside-producing plants. In this issue of Molecular Ecology, Herbertz et al. toss the beta-subunit into the mix, by expressing all nine combinations of three alpha- and three beta-subunits of the milkweed bug Na,K-ATPase and testing their response to a cardenolide from the hostplant. The findings suggest that the diversification and subfunctionalization of genes allow milkweed bugs to balance trade-offs between resistance towards sequestered host plant toxins that protect the bugs from predators, and physiological costs in terms of Na,K-ATPase activity.

Abstract reproduced from the published paper, which is licensed CC BY. Copyright remains with the authors.

Key terms

InsectsMolecular evolutionAdaptationCoevolutionEcological geneticsInvertebrates

Milkweeds in this paper

Plains Milkweed Asclepias pumila

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APA

Milkweed USA. (2026). Escalation by duplication: Milkweed bug trumps Monarch butterfly (listing). Retrieved DATE, from https://milkweedusa.com/research/escalation-by-duplication-milkweed-bug-trumps-monarch-butterfly-2024/

MLA

"Escalation by duplication: Milkweed bug trumps Monarch butterfly (listing)." Milkweed USA, 2026, https://milkweedusa.com/research/escalation-by-duplication-milkweed-bug-trumps-monarch-butterfly-2024/. Accessed DATE.

Chicago

Milkweed USA. "Escalation by duplication: Milkweed bug trumps Monarch butterfly (listing)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/research/escalation-by-duplication-milkweed-bug-trumps-monarch-butterfly-2024/.

BibTeX

@misc{milkweedusa_researchescalationbyduplicat,
  title  = {Escalation by duplication: Milkweed bug trumps Monarch butterfly (listing)},
  author = {{Milkweed USA}},
  year   = {2026},
  url    = {https://milkweedusa.com/research/escalation-by-duplication-milkweed-bug-trumps-monarch-butterfly-2024/},
  note   = {Accessed DATE}
}

Escalation by duplication: Milkweed bug trumps Monarch butterfly