Evolutionary biologists are still critically examining the mechanisms of evolution in detail. The Science magazine has just published a summary by Elizabeth Pennisi of a paper in Evolution on work done by Schemske and Bierzychudek on the plant desert snow (Linanthus parryae). As this paper requires a subscription to read, I’ll abridge the summary.
There are two forms of this plant, one with white petals, and one with blue. In some places of the Mojave desert there are large areas of white, and other places the areas are blue, or mixed. It had been thought for 60 years that the differences were due to genetic drift, that is, there were random variations among the distribution of the plants that dictated which plants were where. The dominant variant was the one that got there first. It now seems that this idea is wrong. By a careful analysis of the plants and their environments, including soil type, precipitation, etc., they show that the white and blue variants are each better suited to different locations, and that it is the pressure from the environment that has selected the colour.
What I do not see in this report is whether the researchers have identified what the genetic property is that defines which is successful where. But it’s good to see more evidence that supports the Darwinian hypothesis of selection through natural forces.