Hollow stems on young Macaranga pearsonii trees in Malaysian Borneo are being filled with paralyzed flies instead of ants. A team led by Dan Lestina of the Biology Centre of the Czech Academy of Sciences found that predatory wasps have been moving into the stem chambers that the tree grows to house protective ant colonies, and that the intruders turn them into nurseries stocked with prey.
The study, “Exploitation of an ant-plant mutualism by a cavity-nesting wasp,” appeared in PeerJ on April 15, 2026 (volume 14, article e20984), after acceptance on February 4, according to the Kew repository record. Its senior author is Tom Fayle of Queen Mary University of London.
The Chambers Macaranga Grows for Ants
The tree, not the ant, makes the real estate. As the Queen Mary University of London release explains, Macaranga pearsonii is an ant-plant with hollow stems that evolved to host ant colonies, and the plant also supplies nutritious food bodies. In return the ants defend the plant against leaf-eating insects such as caterpillars. The arrangement has lasted at least 10 million years.
The wasps take the hollow without supplying anything. Adult wasps hunt and paralyze flies, Lestina said, then store them inside the plant’s cavities as food for their young. In the release from the Czech Academy of Sciences institute, he recalled noticing while surveying the plants that many stems had been hollowed out in an unusual way. Some chambers that should have held ant colonies had become prey stores instead, and Asia Research News quotes Lestina describing flies found “being eaten alive by wasp larvae.”
Oil Palm Plantations Versus Logged Forest
The researchers dissected young trees in two habitats in Malaysian Borneo: logged forest and oil palm plantations. Opening the stems was the only way to see what lived inside, and it let the team compare the contents of each chamber, ant colony or wasp nursery, plant by plant. Plants in the plantations were far more likely to host wasps than plants in logged forest, according to the release, which gives no occupancy percentages. ScienceDaily’s summary of the work, from its feed of the study, puts it as wasps invading ant shelters most often in disturbed landscapes such as oil palm plantations.
The wasp goes unnamed in the releases, although a photo caption in the Asia Research News piece shows a Dasyproctus agilis museum specimen without confirming it is the study species. Kalsum Mohd Yusah, a co-author, said researchers do not yet know whether it is native or introduced, but its spread is clearly linked to disturbed landscapes. The repository record for the paper at Royal Botanic Gardens, Kew lists the keywords Macaranga, Crematogaster, Sabah, Dasyproctus, oil palm and habitat change, which suggests the genera and Bornean state involved, though a keyword list is not a species identification. The Asia Research News captions show a Crematogaster ant in the same way, as an illustration and not an identification.
Smaller Ant Colonies Where Wasps Nest
Trees that held wasps had consistently smaller ant colonies than trees that did not. That pattern fits displacement, and the authors say as much, but they stop short of calling it proven. A survey of dissected plants is a snapshot, and a snapshot can show association without showing sequence. Experiments would be needed to show whether the wasps push the ants out or simply move into plants whose ant colonies were already weak.
The stakes run through forest regrowth. Macaranga species are among the first plants to colonize cleared or damaged land, so a weakened plant with a failing bodyguard could slow forest recovery in exactly the places where logging and plantation clearing have opened ground. Fayle drew the longer evolutionary conclusion in the Queen Mary release: “When mutualistic benefits break down, it can drive long-term evolutionary change.” The ants in this partnership defend against caterpillars and other leaf-eaters, and the plantation comparison is the part of the work closest to land that people have already altered; the Kew record lists oil palm and habitat change among the paper’s keywords.
Plants that lose value from their hollow stems may stop investing in them, Fayle warned in coverage by Asia Research News, describing effects of this kind as far less understood than straightforward biodiversity loss. The team does not claim that shift has begun. What it documents is narrower: a tree that keeps growing expensive chambers that wasps use for their own prey is paying for a service it may no longer receive.
The study was funded by the Czech Science Foundation (grant 16-09427S), the Bavarian-Czech Academic Agency (project BTHA-AP-2018-4) and a Czech Operational Programme for research and development, according to the Kew record. Its authors also include Mickal Houadria, Jasmine A. Gavin, Arthur Y.C. Chung, Michal Rindos, Klara Schlosserova and Heike Feldhaar. The open item is the one the team names itself: no experiment yet shows that wasps drive ants out of a plant that ants were holding.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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