Though researchers have known for many years that certain flowers have evolved their colors to attract bees as their pollinators, the same had not been confirmed about those that solely depend on birds to do the job. Now, a report published in the March issue of New Phytologist by a team of Australian scientists, reveals that this is indeed the case, at least for their local flowers.
The research conducted by PhD student Mani Shrestha and Associate Professor Martin Bird from Victoria's Monash School of Biological Sciences, involved collecting the spectral signatures of 200 flowering plants whose main pollinators were known to be birds and bees. The two then performed special phylogenetic analysis on the specimens to test how the colors of the flowers had changed over time.
What they found was that while the colors of the flowers that are currently exclusively pollinated by birds had initially evolved, so that they were attractive to insects, they had more recently changed course and geared their spectral signatures more toward the longer wavelengths i.e. hues of red which, can be more easily seen by birds.
What was even more interesting is that it was not just any type of red reflection, but shades with the specific wavelengths that best matched the four color vision of many Australian native birds. Fortunately, they also happen to be the same colors that make the flowers inconspicuous to insects who have not prove to be very good pollinators. Given that hummingbirds have a similar color vision, the researchers believe that the same color change probably holds true for American flowers that rely exclusively on birds as their pollinators.
What they are not sure of however, is if the flowers in Asia and Africa have also changed their color over time, to make themselves more attractive to birds that are native to those regions. If they can prove that to be true, they may have finally cracked the secret code plants use, to communicate with birds!
For those of you that are unsure of what spectral signature means, it is merely a scientific term to define what colors a person or animal can see. While most living creatures can only see colors from the visible spectrum, there are some birds and insects like bees that can discern ultraviolet rays too.
Resources: monash.edu.au, wikipedia.org,optics4kids.org