In Batesian mimicry, a harmless animal mimics a toxic or otherwise harmful species in order to avoid predation. For example, certain milk snake species will adapt similar colors and patterns to the very toxic coral snake. Milk snakes are completely harmless but predators will see the bright, striped pattern and leave them alone. Until now, all research on Batesian mimicry has focused on animals. In a paper published today (June 13th), researchers show that Batesian mimicry can also exist in plants.
The researchers compared two plants native to New Zealand, Alseuosmia pusilla and Pseudowintera colorata. A. pusilla, also known as toropapa, is a small, edible shrub. The species is known for its sweet-smelling flowers, the name literally translates to “perfumed grove”. P. colorata is another shrub found in the same area. It looks nearly identical but is not edible. P. colorata is known as “pepperwood” because of the hot, numbing sensation left on the tongue if the leaves are eaten. The plants look so similar that it’s been assumed that A. pusilla is mimicking the toxic plant but there was never any real research to back up that claim.
In the study, researchers compared the leaf shapes and sizes of wild A. pusilla and P. colorata. They not only compared the plants to each other but also compared them to other native plants in the forest. The researchers focused on leaf “landmarks” and shapes rather than more basic traits such as length and width. They found that A. pusilla leaves were significantly more likely to resemble P. colorata leaves than any other plant in the forest. The two plants consistently matched in leaf shape, even as they were studied along an altitudinal gradient. Along the gradient, both plants grow differently but they continued to closely resemble each other.
Since herbivores may use very subtle shape differences to determine if a plant is edible, this close mimicry is enough to deter predators. There are most likely many more examples of Batesian mimicry in plants and this research lays a foundation for future studies. The researchers have developed a quantitative method of comparing plant leaf shapes that can now be applied to other species.
Karl G. Yager et al, The significance of shared leaf shape inand, Botany (2016).