Smallest and Largest Plant Pollinators
By: H. Wayne Shew, Ph.D.
NAB Certified Pollen Counter
In a previous blog we looked at the smallest and largest flowers and how they are pollinated. Water is used in transferring pollen in Wolffia, the genus of plants that produces the smallest flowers, while flies are responsible for transfer of pollen in Rafflesia the genus producing the largest flowers.
Like flowers, pollen also varies in size from small to large. However, pollen grains are all microscopic in size and will always be much smaller than the pollinator carrying them, even when considering flies and mosquitoes which can function as pollinators. Thus, the size of the pollinator tells us nothing of the size of the pollen being carried, but it can inform us sometimes of the size and shape of the flower being pollinated.
The most important group of pollinators are the insects, and the group of insects most important in pollination are the bees. Other insects that are important pollinators are moths and butterflies, and to a lesser extent some ants, flies, and beetles. It is hard to pinpoint the smallest pollinator, but certainly two of the smallest natural pollinators are the fig wasp and a group of small bees called panurgine bees. The female fig wasp (Blastophaga psenes) is approximately 1.5 millimeters in length, a little bit longer than the thickness of a microscope slide. This wasp pollinates the common fig Ficus carica and a closely related species F. palmata. There are some 900 species of figs and a corresponding number of species of wasps that pollinate them. There are some 33 genera and a much larger number of species of bees belonging to the subfamily Panurginae, the panurgine bees. These are small to medium size bees; size range from about 5-14 millimeters. Most of these bees are entirely black and are dependent on members of the Asteraceae family of plants as a pollen source; their preference is yellow flowers.
A few other small pollinators include mosquitos (size range about 2-10 millimeters), some species of which are known to pollinate certain orchids, and midges. Midges of the families Ceratopogonidae and Cecidomyiidae, are the only known pollinators of the flowers of the cacao tree. The flowers of the cacao tree are tiny and the midges are the only insects able to successfully work their way into the intricate flowers to effect pollination. There are a large number of species of midges and they vary in size from less than 1 millimeter to approximately 10 millimeters.
The title of largest natural pollinator belongs to the black and white ruffed lemur from Madagascar. The lemurs have a body length of 50-55 centimeters and a tail length of 61-66 centimeters. Adults weigh between 3 and 4.5 kilograms. These lemurs are the principal pollinators of traveler’s palm. The traveler’s palm reaches heights of some 40 feet and the lemurs use their hands to pull open the flower bracts to expose the flower into which the lemur then sticks its long snout and tongue to feed on nectar. The lemur collects pollen on its muzzle and fur and then transports the pollen to the next flower on which it feeds. The fruits that are produced following pollination serve as part of the diet of the lemurs; they are principally frugivorous.
Other large pollinators include the honey possum, a native of Australia, that pollinates flowers of banksia and eucalyptus flowers. The honey possum is a marsupial animal that has a prehensile tail that it uses to hang from the branches of trees. It uses its extremely long tongue to drink nectar from flowers and the nectar along with pollen are the principal components of the honey possum’s diet. The long-pointed snout of the honey possum becomes dusted with pollen when it drinks nectar from flowers and transfers pollen from flower to flower in this manner.
There are also a number of tropical bats that serve as pollinators and other tropical mammals such as bush babies, sugar gliders, and small Australian marsupials in addition to the honey possum.
In addition to mammals and birds serving as pollinators some reptiles are known to play a role in flower pollination. These reptile pollinators include lizards, geckos, and skinks. For example, the Noronha skink in Brazil pollinates the mulungu tree, a member of the legume family. This tree secretes nectar throughout the day and the skink climbs inside the flower to drink the nectar. In the process of foraging for nectar, various parts of the skink’s body contact the anthers of the plant and pollen adheres to the body scales. When the skink visits other flowers some of this pollen is transferred to stigmas, thus effecting pollination. There is a gecko that serves as the pollinator for the flax flower in New Zealand.
Whether big or small the function of the pollinator is to transfer pollen from one flower to another. In some cases like the fig wasp, the process is truly amazing, incredible design to work together–plants and pollinators benefiting one another in the process.
Black and white ruffed lemur