Flowers are increasingly abstaining from sex with bees

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Bee on field pansies: Autonomous reproduction threatens the survival of insects

Photo: Bildbaendiger / imagebroker / IMAGO

Over the past million years, the thing with the bees and the flowers has proven to be an extremely effective symbiosis. While the plants produced nectar to attract the insects, the insects pollinated the plants in return. More than 80 percent of the so-called covered seeds depend on animals for pollination.

However, ongoing environmental changes, such as climate change and the use of pesticides, have caused dramatic insect mortality. Over the past twenty years, the lack of insects has forced flowers to devise a new reproductive strategy, according to a study by the New Phytologist. Instead of "waiting" for fertilization by insects, some flowers now prefer to pollinate themselves. According to the study, they also produced smaller flowers and less nectar than they did 20 to 30 years ago. This, in turn, makes the plants less attractive to bumblebees and other pollinators.

For their study, the researchers compared four natural populations of the pansy (Viola arvensis) in the Paris region. They used seeds from the 20s and 27s that had been kept for research purposes. The analysis showed that the self-generation rate has increased by <> percent in the last <> years.

Evolution towards self-pollination is considered irreversible

The study also shows how quickly evolutionary adaptation processes can take place. Plants have already developed into self-pollinators in the past. This evolutionary process is considered irreversible. In addition, it only has short-term benefits for the plants. Instead, autonomous reproduction is not only problematic for insects: plants that do not have pollinators are more likely to be threatened with extinction.

The changes observed by the researchers could therefore have far-reaching negative consequences for ecosystems. "There is therefore an urgent need to investigate whether these results are symptomatic of a broader pattern among angiosperms (flowering plants) and their pollinators," the study says. It is necessary to look for ways to "reverse this process and break this eco-evolutionary-positive feedback loop".

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