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Unexpected reproductive strategy discovered in Messor ibericus
Scientists have discovered that the Iberian harvester ant (Messor ibericus) displays an unprecedented reproductive system that produces individuals belonging to two distinct species. A team led by biologist Jonathan Romiguier (University of Montpellier) and published in Nature reported that some M. ibericus queens generate males that carry the nuclear genomes of a different species, Messor structor, while retaining M. ibericus mitochondria. The authors term this phenomenon "xenoparous" reproduction — a natural form of cross‑species cloning that sustains a male‑only lineage cloned through the eggs (ova) of one species but genetically matching another.
Scientific background: haplodiploidy and colony caste production
Ants exhibit haplodiploidy: females are diploid (two chromosome sets) and males are haploid (one chromosome set). Queens can influence colony structure by fertilizing eggs (producing diploid females that become workers or queens) or leaving eggs unfertilized to produce haploid males. This control underpins colony division of labor and caste determination. Hybridization between ant species is known in some genera, and social insects already show complex reproductive systems including cloning; however, cloning that produces individuals of a different species has not been documented until now.
Study design, genomic evidence, and proposed mechanism
Romiguier and collaborators sampled 50 nests across southern France, collecting 132 males from 26 M. ibericus colonies. Approximately half of those males resembled M. structor by morphology. Genomic analyses revealed a striking pattern: these males carried nuclear DNA consistent with M. structor but mitochondria inherited from M. ibericus. Because mitochondria are maternally inherited, the combined signature indicates the males were produced inside M. ibericus queens yet possess a distinctly different nuclear genome.
The research team proposes that M. ibericus queens clone M. structor males by permitting sperm from M. structor‑type males to enter eggs, but then eliminating the egg’s maternal nuclear material prior to full fertilization. The result is an egg that develops as a haploid male genetically matching M. structor while maintaining M. ibericus mitochondria. These cloned males then mate within the colony to produce hybrid diploid workers (genetically mixed offspring) needed for colony function. This two‑species reproductive loop creates a male lineage cloned across species boundaries while also generating hybrid workers.
Key discoveries and evolutionary implications
This discovery raises several important biological questions. Cross‑species cloning challenges standard views of reproductive isolation and speciation: here, genomes from lineages that diverged over five million years ago are maintained and propagated through an unusual reproductive cycle. Maintaining a supply of genetically foreign males as a reproductive resource may be a strategy to secure sperm while producing hybrid workers optimized for colony roles.
The mechanism could influence gene flow, social structure, and adaptation. It suggests novel forms of reproductive cheating and cooperation in social insects and expands known mechanisms for maintaining distinct genetic lineages in sympatry. From an applied perspective, understanding this system could inform pest management strategies that exploit reproductive vulnerabilities in ant colonies.
Expert Insight
Dr. Elena Márquez, evolutionary geneticist (fictional), comments: "This system is remarkable because it separates mitochondrial lineage from nuclear identity across species boundaries. If validated across broader populations, it forces us to reconsider how reproductive systems can circumvent species barriers to meet social and ecological needs."
Michael Goodisman, an evolutionary biologist at Georgia Tech who was not involved in the study, told Science that the finding "is almost impossible to believe and pushes our understanding of evolutionary biology. Just when you think you’ve seen it all, social insects reveal another surprise." His reaction underscores how social insect biology continues to surprise researchers and reshape theoretical frameworks.
Conclusion
The report of xenoparous reproduction in Messor ibericus reveals a striking, previously undocumented reproductive strategy: queens clonally produce males that belong genetically to another species and then use those males to create hybrid workers. The finding blends genomics, behavior, and evolutionary theory, opening new avenues to study speciation, social evolution, and genetic control mechanisms in eusocial insects. Future research will need to clarify the precise cellular mechanisms, geographic distribution, and evolutionary origins of this extraordinary system.
Source: nature
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