Spring
Adrian Thomas marvels at the miracle of insect pollination, and what we can do to help
Pollination by insects is, if you stop to think about it, pretty astonishing. An insect is drawn to a plant’s special landing pad – its flower – with the offer of food and drink. While tucking in, it picks up grains of pollen, effectively the male sperm of the plant, and unwittingly couriers them to other flowers where they fertilise the female egg cells.
It means that pollinators are the essential link that allow flowering plants to produce seeds and produce the next generation. Pollination by insects is surprisingly recent in Earth’s history. If you condense the time our planet has been in existence into a single day, then it only began about 45 minutes before midnight.
The emergence of pollinators went hand-in-hand with the evolution of the first flowers. It turned out to be one of the most important and successful relationships our world has ever seen. For a plant, having your pollen delivered personally takes out much of the risk of just tossing it into the wind, which is what they had done previously. It was so successful that flowering plants, you could say, blossomed! They now make up an estimated 85-90% of all plant species in the world, although, in terms of sheer abundance, wind-pollinated plants are still widespread because of the giant conifer forests, wheatfields and grasslands.
As the flowering plants proliferated, so did the number of species of pollinating insect – there are now thought to be in the order of 200,000 worldwide. Even in the UK, there are at least 1,500, of which about 270 are bees, 280 hoverflies, and then a host of other flies and beetles and wasps. We shouldn’t forget that a few other creatures are pollinators, such as some specialist birds and bats, but in the UK it is insects that do the lion’s share.
In the evolutionary race for survival, plants had to become ever more flashy and generous to secure the pollinators’ vital services. Flowers became more colourful and showier; they began to emit tempting scents; and some evolved to serve just certain types of insects. In effect, the contract between flower and insect species became locked in and exclusive. And, where insect pollination started with insects eating pollen, many flowers started to offer up sticky sugar as the reward – nectar.
