The relationships between Pollinators and Plants
Pollinators and flowers go hand in hand, we cannot have one without the other. Pollinators are the vector by which the plants achieve fertilisation thought the transfer of pollen from the male part of a flower to the female part of another flower. For the pollinators the flowers represent their food source.
This relationship between insects and flowers began over 160 million years ago when the first flowering plants evolved. At first these simple flowers did not produce nectar but were pollinated by Thrips and Beetles which visited the flowers to eat the nutritious pollen. The plants learnt that they could entice insects to transport their precious pollen grains to flowers of neighbouring plants by secreting excess sugars in the form of a nectar.
This triggered an evolutionary arms race with plants developing ever more elaborate methods of attracting pollinating insects to their flowers including the use of scent lures and for the insect’s ever more efficient adaptations for transporting pollen and accessing the nectar presented to them. Even today beetles represent the largest group of pollinating insects on the planet by sheer numbers and are responsible for pollinating 88% of the world’s estimated 240,000 species of flowering plants.
The first Bees appeared around 100 million years ago with Bumble bees and Honey bees evolving in the last 30 million years. Bees are more efficient pollinators of flowers than many other insects due to their unique ‘plumose’ hairs which cover their bodies. These branched hairs are more efficient at clinging to pollen which the bees can then transport to an unrelated flower to achieve pollination.
Flowers offer food for pollinators in 2 forms.
Many plants secrete nectar from glands which the insects feed upon. Nectar is rich in soluble sugars which are simple carbohydrates and give the insects the energy they need for their metabolic activities. Flying is an energy demanding activity which means many insects spend a great deal of time flying from flower to flower in search of nectar. Nectar also contains trace elements, vitamins and micro nutrients needed to maintain healthy body functions.
Not all plants produce nectar (many early spring and winter flowering plants can’t create soluble sugars in cold temperatures) and some plants produce nectar in greater abundance than others. Some nectar sources also contain more sugar than others which can make them more appealing to pollinators.
Different pollinators have different lengths of tongues which means not all species are attracted by the same flowers. Those with shorter tongues will be better adapted to access nectar on simple open flowers which shallow nectar wells whilst long tongues species are better equipped to take advantage of flowers with long trumpet shaped structures.
Many plants have specific requirements which must be fulfilled before they will produce nectar. These can be dependent on climatic variables such as temperature, exposure to sunlight, moisture content of the soil and air humidity.
For this reason it’s important to plant a wide variety of flower types to cater for the widest range of pollinators.