The origin of the flowering plants is, as DarkSyde observes, critical to the world as we know it. Not just because chocolate is lovely, as are roses. But because honey tastes good, and the diversity of butterflies is a never-ending source of joy to us all. If not for flowering plants, the insects would be a drab bunch.
It’s hardly surprising that insect diversity and plant diversity have followed one another closely through geological history. Like so many romances, the story of plants and insects is a love-hate relationship, with happiness built by finding a happy middle.
The bee in the photograph above the fold is a member of the family Halictidae, a sweat bee, and it is collecting pollen. Bees get protein from pollen, and get sugar from the nectar at the base of the flower. The turn that protein and sugar into honey for their young, and as they fly from flower to flower, some of the pollen that stuck to them in one flower gets transferred to the next. This is why farmers will hire beekeepers to set their hives up in orchards and fields, because those bees are necessary to produce the fruits we all enjoy.
Not all flowers are as promiscuous as the rose that bee is pollinating. A flower that lets any insect at all get to the pollen will waste a lot of pollen. The bee might not fly to another rose of the same species, and might not have come from a rose of the same species. They have to waste energy producing excess pollen and attracting more bees so that enough will come by to ensure that some bee will eventually do the job.
Orchids have chosen a different path. Their elaborate flower shapes often wind up resembling a very specific species of insects, and will produce odors similar to that one insect’s pheromones. The fly or bee will be fooled into thinking he has found a mate, and in tussling with the tricky petals, will get covered in pollen, off he’ll go, and the next female he thinks he sees may well be another orchid flower, where he can release some of the old pollen and inadvertently get some more. Of course, as different species of orchids come into contact, the ones that are most effective at attracting insects that are as different from other orchids will do the best at pollinating and getting pollinated, and thus species boundaries will get reinforced, and orchid diversity skyrockets.
By the same token, insects that can recognize the difference between a flower and a mate will leave more offspring, and the ones that have the most distinct mating signals will waste less time on flowers. This will create and strengthen mating boundaries between populations of insects, promoting speciation. That tug-of-war has given us the diversity of orchids we see in gardens and flower shops, and on our loved ones during this Valentine’s Day.