Study reveals that as insect populations in Europe fall, so some plants are turning to self-pollination
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If you’re old enough to remember the 1980s then, alongside big hair and mismatched glow-in-the-dark socks, you may well recall that having a picnic on a summer’s day meant engaging in a never-ending battle with insects.
Fast-forward four decades, and a picnic of today is rarely plagued by the same quantity of uninvited insect diners. And that’s because, as study after study has revealed, Europe’s insects are in a cataclysmic decline, with populations dropping by up to 70-80 per cent in some areas.
While this is good news for bite-free picnics, it’s bad news for the environment. Insects sit at the bottom of the food chain and a lack of insects spells trouble for creatures higher up the chain. It also spells trouble for plants reliant on insects for pollination.
All plants need to be pollinated in order to reproduce. Some use wind to pollinate. Others use insects and other creatures. In most cases, insects and other pollinating animals are attracted to a plant by its flower, and the nectar contained within. But producing flowers and nectar takes up a lot of energy and so if plants start to pollinate by another method, then the high energy production of flowers is no longer so important and the plant may scale back its flower production.
And now, as if to confirm this, a new study has revealed that some flowering plants might be adapting to an environment deprived of pollinating insects by increasingly turning to self-pollination. The study authors speculate that this example of rapid evolution is likely due to the dramatic decline in insect pollinator species.
The study, which was published in the journal New Phytologist Foundation on 19 December, shows that the flowers of field pansies growing near Paris are ten per cent smaller and produce 20 per cent less nectar than field pansies growing in the same fields 20 to 30 years ago. They are also visited less frequently by insects, and the plants appear to be turning to self-pollination.
To come to these conclusions, the team from the French National Centre for Scientific Research compared the pansies of today with pansies resurrected in a laboratory from seeds collected in the same place between 1992 and 2001.
The results of this study show a vicious circle developing in which the decline in pollinating insects leads to reduced nectar production by flowers, which could further exacerbate the decline of insect populations, leading to the plant’s further reducing reliance on insects.
This isn’t the first case of high-speed evolution discovered in plants. Foxgloves, which are native to Europe, are pollinated by bumblebees. But, when they were introduced to parts of central and southern America 200 years ago, they quickly changed the shape of their flowers so that they could be pollinated by nectar-seeking hummingbirds instead of bees.
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