Morphological changes in female reproductive organs in the

What this paper is about

The African monarch has four color forms whose ranges meet in East Africa, and some populations carry Spiroplasma, a bacterium that kills male embryos.

The authors measured female reproductive organs across these populations, looking for the morphological variation that sexual conflict is expected to produce.

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

Abstract

BackgroundSexual selection and conflicts within and between sexes promote morphological diversity of reproductive traits within species. Variation in the morphology of diagnostic reproductive characters within species offer an excellent opportunity to study these evolutionary processes as drivers of species diversification. The African monarch, Danaus chrysippus (Linnaeus, 1758), is widespread across Africa. The species is polytypic, with the respective geographical ranges of the four colour morphs only overlapping in East Africa. Furthermore, some of the populations host an endosymbiotic bacterium, Spiroplasma, which induces son-killing and distorts the local host population sex-ratio, creating sexual conflicts between the females seeking to optimize their fecundity and the limited mating capacity of the rare males.MethodsWe dissected females from Kenya, Rwanda and South Africa, where Spiroplasma vary in presence and prevalence (high, variable and absent, respectively), and conducted microscopy imaging of their reproductive organs. We then characterized the effect of population, female body size, and female mating status, on the size and shape of different genitalia characters of the D. chrysippus female butterflies.ResultsWe showed that although the general morphology of the organs is conserved in D. chrysippus, female genitalia vary in size and shape between and within populations. The virgin females have smaller organs, while the same organs were expanded in mated females. Females from highly female-biased populations, where the male-killing Spiroplasma is prevalent, also have a larger area of their corpus bursae covered with signa structures. However, this pattern occurs because a larger proportion of the females remains virgin in the female-biased populations rather than because of male depletion due to the symbiont, as males from sex-ratio distorted populations did not produce significantly smaller nutritious spermatophores.

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

Key terms

Nuptial giftSignumBacterial SymbiosisSex-ratio DistortionCorpus Bursa

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APA

Milkweed USA. (2026). Morphological changes in female reproductive organs in the African monarch butterfly, host to a male-killing Spiroplasma (listing). Retrieved DATE, from https://milkweedusa.com/research/morphological-changes-in-female-reproductive-organs-in-the-african-2023/

MLA

"Morphological changes in female reproductive organs in the African monarch butterfly, host to a male-killing Spiroplasma (listing)." Milkweed USA, 2026, https://milkweedusa.com/research/morphological-changes-in-female-reproductive-organs-in-the-african-2023/. Accessed DATE.

Chicago

Milkweed USA. "Morphological changes in female reproductive organs in the African monarch butterfly, host to a male-killing Spiroplasma (listing)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/research/morphological-changes-in-female-reproductive-organs-in-the-african-2023/.

BibTeX

@misc{milkweedusa_researchmorphologicalchanges,
  title  = {Morphological changes in female reproductive organs in the African monarch butterfly, host to a male-killing Spiroplasma (listing)},
  author = {{Milkweed USA}},
  year   = {2026},
  url    = {https://milkweedusa.com/research/morphological-changes-in-female-reproductive-organs-in-the-african-2023/},
  note   = {Accessed DATE}
}