Rouge Valley Conservation Centre
Nature Notes
By Steve Gahbauer
June 2008
Pollinators.
It can happen under the cover of night or in broad daylight. It can happen in the deep dark forest or in the wide open fields. It is one of the most important biological processes on our planet, yet it remains a mystery to many. So, let's look at some of the great secrets in the private life of plants – pollination.
Pollinators can be natural forces like wind or water, but for today I will stick with animals doing this vital job. They help to transfer pollen from the male part of a flower (anther) to the female part (stigma) inadvertently as they feed. While the pollinator searches for sustenance, pollen from the anther sticks to body parts and as it moves to another plant the pollen is transferred to the stigma and fertilization occurs. This “service” that pollinators provide is essential for reproduction of nearly 80% of the seed-producing flowering plant species on earth. Pollination creates fertile seeds that contain the promise of renewed life, year after year and generation after generation. Pollinators are often referred to as “keystone species” because many other species depend on them. They play a critical role in the function of ecosystems. Without pollination, many plants could not reproduce and food webs would collapse. Without pollination, the world would be a different place. We would not have apples, bananas, tomatoes, chocolate, fibres, fats and oils, or spices and condiments.
Canada is home to more than 1,000 species of pollinators – a tireless army of insects, birds and mammals that make it happen. That includes bees and wasps, bumblebees, hummingbirds, butterflies, beetles and, in the tropics, fruit bats and even primates. When I was exploring wildlife in Madagascar, I learned that mouse lemurs are pollinators too. They are night creatures and lick the nectar of baobab tree blossoms, which bloom only in the middle of the night during the rainy season. I think that among pollinators they are the only primates, and certainly the smallest; mouse lemurs are not much bigger than a fat Norway rat.
Flowering plants include broadleaf trees and garden vegetables, rice, wheat and other grains, and most fruits. Some ferns and mosses and many conifers are also seed producers. Pines, spruces and firs among them are present in the Rouge Valley. They don't have flowers but produce male and female cones. Pollen grains from the male cones are transferred to female cones by pollinators and fertilize the latter. The seeds grow up naked on the cones without ever developing fruit.
In the spirit of synergetic partnership in nature, pollinators have adapted along with their favourite plants. In turn, plants employ specific strategies to attract their benefactors. They use colour, patterns, shapes, scent and timing to lure pollinators, and so food and reproduction needs are met in a miraculous way.
Pollinators also contribute to biodiversity in at least two ways. First, genetic diversity is made possible by pollen transfer from one plant to another. A plant population with a diverse genetic make-up is better able to fight off diseases and parasites and can adapt more successfully to climate change. Second, the success of seed-producing plants increases species diversity, resulting in healthier ecosystems.
We tend to take the presence of pollinators for granted as they never seem to be in short supply. But perceptions can be deceiving. The main threats facing pollinators are all too familiar and are mainly the result of human activities – the use of pesticides, toxic chemicals, imported diseases, and fragmentation or outright loss of habitat. Pollinators need healthy habitats for foraging and nesting. Many do not travel great distances, so they need sites close to abundant sources of their life necessities.
Air pollution from industrial plants, power generating stations and cars destroys the fragrance of flowers and inhibits the ability of pollinators to follow scent trails to their food source. This could partially explain why wild populations of some pollinators are declining – especially bees who are among the most important pollinators. Of the roughly 2,000 bee species in Canada, the bumblebee is most likely the best known, next to the honeybee.
Bumblebees range in size between 13 and 25 mm and live in small nests underground. The females have a wide hollow “basket” on their hind legs for collecting pollen. Only the queen lives to the next spring, the rest of the bumblebee colony dies in the winter. Bumblebees do not swarm. They fly at a rate of about 3 m per second. They are often the first pollinators in early spring and the last to still be active in the fall, collecting nectar and pollen from a wide variety of plants. During their one-year life span bumblebees go through four development stages: egg, larva, pupa and adult. The adult stage lasts only 3–4 weeks.
In an industrial, urbanized and highly specialized culture such as ours, we tend to lose sight of the fact that the most basic activity of any living thing, including humans, is still the procurement of food. In the animal world, obtaining food is what absorbs most of the energy of wildlife, the rest being devoted to procreation. And while pollinators are gathering food, they also fertilize plants in the process. This is one of the marvels of nature that never cease to amaze us and that we can readily observe right here in our Rouge Park. Look for pollinators on your next hike.
Sources: Canadian Wildlife Federation and personal field notes.
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