No, your eyes are not playing tricks on you. This flower produces red nectar. Known scientifically as Nescodon mauritianus, this member of the bellflower family (Campanulaceae) grows only on the island of Mauritius. Although it is not alone in producing colored nectar (at least 60 other plant species do so as well) the striking contrast of the red nectar against the blue corolla had botanists wondering what exactly these plants are attracting.
Of course, the obvious answer were birds. It is no mystery that birds see in color much in the same way as us humans. However, multiple tests and observations demonstrated that birds were not the best pollinators for these flowers. In fact, the birds functioned mainly as thieves, stealing nectar without actually coming into contact with any of the necessary floral parts. The same thing happened to a Mauritian relative of the mallows named Trochetia blackburniana, which also produces colored nectar.
To better understand the signalling mechanisms of these flowers, a team of researchers utilized a series of floral models. By filling the models with different colored nectar, they were able to better understand what they are attracting. As it turns out, the answer to this mystery are geckos.
Living alongside these plants is a genus of day gecko called Phelsuma. They are endemic to Mauritius and can frequently be found visiting nectar-producing flowers in search of energy-rich nectar. By observing how the geckos responded to various color combinations, the team was able to discover that these geckos seem to prefer red and yellow nectar over clear. What's more, their feeding habits once inside the flower puts them in direct contact with the anthers and the stigma. Thus, the geckos function as the most effective pollinators for these plants.
The team now feels that the colored nectar of these species serves as an honest reward for pollinating geckos. It is a stark indication that a reward is present. It is possible that because these geckos rely on brightly colored markings when interacting with each other, the selection for brightly colored floral signals has been favored in the evolution of these gecko pollinated plants. More work needs to be done to say for certain. What we do know for sure is that these day geckos are important pollinators in Mauritian ecosystems.
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