FLOWERS EVOLVE TOO

One of the stranger stories in the environmental press recently was about a little bulb in China. It is a fritillary, prized for use in traditional medicine. It has a pretty greenish flower of a similar shape to those of our British snake’s head fritillary. It stands out starkly against the grey rocky habitat where it grows and so is easy to find and pick. Enter evolution and selective pressure: this bulb has developed grey flowers and foliage that camouflage it and make it much harder to see by the pickers, so escaping their predation. Presumably, it can still be found by its insect pollinators, though.

I think many of us tend to forget just how dynamic the natural world is. We all learn about Darwin and evolution, and many of us go on to study genetics, but somehow there is a mismatch between the work that consumes us and our observations of the species all around us every day, perhaps because evolutionary change usually  happens very slowly. The Chinese fritillary is an exception because of the speed of the transformation from green and yellow plants to grey ones, fast enough to be noticed by those gathering the flowers.

In evolutionary terms, flowers came along quite recently: it took 340 million years for them to appear after the first land plants that arose 470 million years ago. Once they had appeared, though, flowering plants (angiosperms) spread worldwide with their impressive colonising ability, and have become amazingly diverse in their shapes and behaviour. But shaped by what? Well, by selection of genotypes through the wondrous process of sexual reproduction and survival of the fittest in habitats where seeds and other propagules can spread, with soil (substratum), climate and serendipity being overriding factors for early colonisers in most cases.

What is interesting, though, is that plants are also highly reactive to things that eat them and things that pollinate them. Grazing drives the production of secondary metabolites in their tissues, bad-tasting or actually toxic and, wind aside, invertebrate and other animal pollinators drive flower shape, colour and perfume inter alia. What is unusual in the Chinese fritillary case is that it is human picking that has driven a rapid change for the plants to become camouflaged. I have never heard of another instance quite like this.

The vegetation on Betts sites is, of course, subject to influences of the environment just like anywhere else, perhaps more so in some ways because of the strong selective pressures of one kind or another on urban greenspace. Look carefully at any path and you will see a gradient from edge to edge from plants that like the well-lit, relatively untrampled edges, through those that can withstand some footfall pressure (and perhaps inputs from passing dogs), and then through trample-tolerant, ground-hugging plants in patchy barer ground along the centre.

Betts Ecology scientists and grounds staff are aware of the different pressures on, and responses of, plants in different situations, and we direct our management practices to keep a variety of land-use to maintain botanical diversity accordingly.

© Betts Ecology