Sex facilitators for plants
"Sex has always been difficult for plants, because they cannot move. If one cannot move, then finding a suitable partner and exchanging sex cells with them poses something of an obstacle. The plant equivalent of sperm is pollen, and the challenge facing a plant is how to get its pollen to the female reproductive parts of another plant; not easy if one is rooted to the ground. The early solution, and one still used by some plants to this day, is to use the wind. One hundred and thirty-five million years ago almost all plants scattered their pollen on the wind and hoped against hope that a tiny proportion of it would, by chance, land on a female flower. This is, as you might imagine, a very inefficient and wasteful system, with perhaps 99.99 per cent of the pollen going to waste - falling on the ground or blowing out to sea. As a result they had to produce an awful lot.
Nature abhors waste, and it was only a matter of time before the blind
stumbling of evolution arrived at a better solution in the form of
insects. Pollen is very nutritious. Some winged insects now began to
feed upon it and before long some became specialists in eating pollen.
Flying from plant to plant in search of their food, these insects
accidentally carried pollen grains upon their bodies, trapped amongst
hairs or in the joints between their segments. When the occasional
pollen grain fell off the insect on to the female parts of a flower,
that flower was pollinated, and so insects became the first pollinators,
sex facilitators for plants. A mutualistic relationship had begun which
was to change the appearance of the earth. Although much of the pollen
was consumed by the insects, this was still a vast improvement for the
plants compared to scattering their pollen to the wind.
To start with, insects had to seek out the unimpressive brown or green flowers amongst the surrounding foliage. It was now to the advantage of plants to advertise the location of their flowers, so that they could be more quickly found and to attract insects away from their competitors. So began the longest marketing campaign in history, with the early water lilies and magnolias the first plants to evolve petals, conspicuously white against the forests of green. The first pollinators may have been beetles, which many water lilies still rely on to this day. With this new reliable means of pollination, insect-pollinated plants became enormously successful and diversified. Different plants now began vying with one another for insect attention, evolving bright colours, patterns and elaborate shapes, and the land became clothed in flowers. In this battle to attract pollinators, some flowers evolved an additional weapon - they began producing sugar-rich nectar as an extra reward. As these plants proliferated, so the opportunities for insects to specialise grew, and butterflies and some flies evolved long, tubular mouthparts with which to suck up nectar. The most specialised and successful group to emerge were the bees, the masters of gathering nectar and pollen to this day."
Source:
https://www.scientificamerican.com/article/the-beguiling-history-of-bees-excerpt/
Excerpted with permission from the book A Sting in the Tale: My Adventures with Bumblebees, by Dave Goulson.