The ancestral colour vision of insects, based on UV, blue and green sensitive sensory organs, does not allow reliable detection of red flowers. Therefore, pollinators of plants
with flowers that reflect in the red part of the spectrum have developed specialised, redsensitive sensilla. The most typical red-flowering plant in Europe is the field poppy (Papaver rhoeas), an annual native to the eastern Mediterranean, which has spread beyond its natural range with the help of man, especially agriculture, among crops. As the climate changes, both flora and fauna change, and the field poppy has had to adapt and become visible to a new range of pollinators. In eastern and southern Europe, the
species is pollinated by beetles of the family Glaphyridae, which are absent outside the Mediterranean. These beetles have the specialized photoreceptors to detect red colours.
In central Europe these beetles are not present, therefore the poppy has evolved flowers with a modified reflectance spectrum, with an additional peak in the ultraviolet, and thus has become visible to other effective pollinators such as Hymenopterans. We surveyed a transect along the north Adriatic coast and found a natural border at Lake Skadar that separates the two flower variants in the field poppy. We found flowers with low and others with high reflectance in the UV part of the spectrum. In the southern part of the
lake the poppies have low UV reflectance and the glaphyrid beetles are present, while north of the lake, the beetles from this family are absent and the poppies have evolved
a high UV reflectance. The results show an extremely close relationship between visual signals on plants and pollinator vision.
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