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03/14/2017 17:00

Flies and bees act like plant cultivators

Nathalie Huber Kommunikation
Universität Zürich

    Pollinator insects accelerate plant evolution, but a plant changes in different ways depending on the pollinator. After only nine generations, the same plant is larger and more fragrant if pollinated by bumblebees rather than flies, as a study conducted by evolutionary biologists from the University of Zurich reveals.

    Not much plant sex happens without pollinator insects: Bees, flies or butterflies transfer the male pollen grains to the stigma of a plant’s female style, thereby ensuring its sexual reproduction. Researchers from the Department of Systematic and Evolutionary Botany at the University of Zurich now reveal that pollinator insects also have a surprisingly strong influence on plant evolution.


    Plants pollinated by bumblebees become more fragrant

    For their experiment, UZH professor Florian Schiestl and doctoral student Daniel Gervasi used field mustard – a kind of cabbage species and a close relative of oilseed rape. The researchers allowed one plant group to be pollinated solely by bumblebees for nine generations, another only by hoverflies and a third by hand. Afterwards they analyzed the plants, “which differed greatly,” as Florian Schiestl explains. The plants pollinated by bumblebees were larger and had more fragrant flowers with a greater UV color component, which bees and their relatives see. The plants pollinated by hoverflies, on the other hand, were smaller, their flowers were less fragrant and they self-pollinated considerably more. According to Schiestl, the mechanism of evolutionary change is fact that different pollinators differ in their preferences and thus preferentially cross-pollinate specific plant individuals, much like a plant breeder using individuals with favorable properties. The flies’ considerably lower pollination efficiency is the cause of the increase in self-pollination. The plants essentially help themselves if the pollinator transfers too little pollen.


    Pollinator insects hasten plant evolution

    The fact that the plants change so significantly already after nine generations came as a surprise to the researchers: “The traditional assumption is that evolution is a slow process,” explains Schiestl. The evolutionary biologist from UZH draws the following conclusion from his results: “A change in the composition of pollinator insects in natural habitats can trigger a rapid evolutionary transformation in plants.” This is particularly interesting as certain pollinator insects such as bees have been vastly decimated by the extensive use of pesticides and the depletion of the landscape in recent decades. According to Schiestl, it would thus be conceivable for plants to increasingly rely on flies as pollinators, which would result in the evolution of weaker flower fragrances and more self-pollination. In the longer term, this would reduce a plant population’s genetic variability and the plants would become more susceptible to disease.


    Literature:

    Daniel Gervasi, Florian Schiestl. Real-time divergent evolution in plants driven by pollinators. Nature Communications. March 14, 2017. DOI: 10.1038/NCOMMS14691



    Contact:

    Prof. Florian Schiestl

    Department of Systematic and Evolutionary Botany

    University of Zurich

    Phone: +41 44 634 84 09

    E-mail: florian.schiestl@systbot.uzh.ch


    More information:

    http://www.media.uzh.ch/en.html


    Images

    Field mustard: The plant pollinated by bumblebees is larger (left) than the plant pollinated by hoverflies.
    Field mustard: The plant pollinated by bumblebees is larger (left) than the plant pollinated by hove ...
    Picture: UZH
    None


    Criteria of this press release:
    Journalists
    Biology, Environment / ecology, Zoology / agricultural and forest sciences
    transregional, national
    Research results, Scientific Publications
    English


     

    Field mustard: The plant pollinated by bumblebees is larger (left) than the plant pollinated by hoverflies.


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