White and Pink-flowered Spring Beauty
Spring Beauty, Claytonia virginica, is a familiar and welcome spring ephemeral that carpets the forest floor at this time of year. Within a population, its blossoms range in color from white to a deep pink. You don’t usually find a range of colors within a given population, as one color is often more successful at reproducing and it eventually becomes dominant, while the other colors are eliminated.
There is a reason why both colors of Spring Beauty continue to flourish within a given population. A red pigment interacts with two chemicals (flavenols) to produce the range of color. Plants with a high percentage of flavenols produce white flowers. These flavenols are a deterrent to herbivores, so in years when there are lots of slugs, white-flowered plants are more successful in producing seeds. This would lead one to conclude that eventually pink-flowered plants would diminish in number. However, white-flowered Spring Beauty is also parasitized by a type of fungus called a rust, Puccinia mariae-wilsoniae, which causes orange spotting and often serious deformation of the plant (see photo).
Thus, in years when slugs are numerous, white-flowered Spring Beauty flourishes and produces seeds. In years when slugs are not numerous but fungal infection is high, pink- flowered plants reproduce more successfully. This sporadic success of both white and pink Spring Beauty is why we continue to find them both in the same population.
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