The relationship history between plants and their pollinator is a fascinating example of coevolution. Indeed, the survival of entomogenous plants depends directly on the presence of pollinating insects and vice-versa. This has allowed that his relationship becomes an indissoluble relationship of mutual survival based on a intense and complicated exchange of messages. Their connection, in fact, has a long history and has been built on method of communication that becomes more and more sophisticated and appears to us still not completely clear. Nowadays we know that the messages that plants produced are of various nature and stimulates different sensory organs of pollinating insects in order to orient them. The megaphone that allowed this communication is represented by the flower; it is a way for the plant to emit multiple information in different “language”. The union of this signals of different nature produced a clear messages for pollinator that in this way is able to recognize the presence and the specificity satisfying his need of nectar and at the same time costituting a fondamental piece of the reproduction of many plants pollinating different individuals of the same plant spieces.
The strategy of beauty
The most striking communicative way that the plant use is undoubtedly the visual one. The colors and the geometries of the flower represent a signal for a pollinator. The nature of this signal could be vexillary or selective. Flowers, being the reproductive organs of plants, are often differentiated into fertile and sterile flowers. Sterile flowers are found at the edges of floral apparatus and have a vexillary function, just has in the case of the common daisy. Anither foundamental actractive factoris the number of flowers; hence the need of some plants to form wonderful inflorences. The last mechanism of attraction used by the plant is the pseudo-crystalline geometry of some flowers: the disposition and the number of petals follow precise geometrical and mathematical schemes, such as the golden section and the Fibonacci sequence.
The size, shape and bright colours of flowers are an irresistible attraction for pollinators, however, they can also be a selective factor. On a chromatic level, plants can make themself visible to specific insects by playing on the wavelength perceived by the eye of their specific pollinator. In this way, each flower is visible only to its pollinator which, once visited a flower of one species, will pollinate another flower of the same species. For example, the dark spots on the petals of flowers of some plants, reflecting UV rays, act as landing strips that guide pollinators that perceive ultraviolet light ti the nectar.
Another mechanism to improve pollinators’ specificity is flower shape which can limit access to the nectar to only certain insects. An example is fig flowers, which are only accessible to the blastophaga, a small wasp that can enter the flower receptacle.
To learn more, visit our blog for part two next week!