How do pollinators paint the landscape with colour?

When you look at a patch of flowers, you often see clusters of colour. Even when a single species can have many different colours, you get patches. Why? How does a plant know to grow with this colour and not that colour? The answer is it doesn’t. The colour is set by the genes in its seed, so how do those genes get there? Are pollinators somehow involved in creating these patches of similar colours? This is a problem that Jurene Kemp and colleagues have been investigating.

The flowers that the team studied are daisies in Namaqualand, South Africa. Namaqualand is an arid region but, for a brief period, it bursts into colour when the daisies bloom. For a short time, the flowers are open to exchange pollen with other plants. They rarely self-pollinate, so the next generation should be a scrambled version of the current generation. After seeds are set, they die back. When the new daisies bloom next year, similar patterns of colour remain. It seems there is some selection happening.

Kemp’s team examined the blooms. They assigned the plant species into colour pattern categories (CPCs). The categories were based on how a pollinator would see the complex bulls-eye patterns of the flowers.

What they found was that some categories had more plant species than others. This suggests that some patterns have a competitive advantage. They also found that each community has a dominant pollinator. The colour patterns are geared to attract this pollinator. The results lead to some interesting conclusions.

First, attracting pollinators to the plants in a community doesn’t have to be a competition. If there are relatively few pollinator species, it makes more sense for plants to share visitors than compete.

Also, because daisies are so open, it has been thought that daisies are generalists. Kemp and colleagues show the daisies aren’t indiscriminately attracting passing visitors for pollination. The specific colour patterns attract only a few potential pollinators. Instead of being open to anything, daisies might be targeting only flies. Or even only certain fly species.

It means that when you see blocks of colour in the landscape, the view is far from random noise.