However, until recently, very little was known about more ancient modes of insect pollination, those that predated the appearance of flowering plants or that occurred before angiosperms became dominant in terrestrial ecosystems. To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
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The yucca moth larvae cannot survive without yucca seeds to eat. The system works because the larvae eat only some—not all—of the seeds. Plant-pollinator mutualisms are believed to be at least partly responsible for the large diversity of flowering plant species that showed up million years ago. Approximately species of fig tree are pollinated by approximately species of fig wasps.
Most of the wasps pollinate only one or two species of fig, so the mutualisms are very specific. How does this happen? Think of it this way. Say you have a mountain called Big Rock Mountain. To the east you have a population of flowers called Awesome Red Daisies that are pollinated by bees called Stinging Mothers. Awesome Red Daisies have 6 really important genes: a, b, c, d, e, and f. All these genes are pretty common except for c. There are only a few c genes in the population—it is a gene that makes the flower yellow.
Stinging Mothers have 8 really important genes: 1, 2, 3, 4, 5, 6, 7, 8. All are pretty common except 2. Gene 2 gives the bees a long tongue. As a rule Stinging Mothers have short tongues, although a few have long tongues. Life is fine on the east side of Big Rock Mountain until one day a tremendous storm the biggest storm in un-recorded history blows some Awesome Red Daisy seeds and a few of the Stinging Mothers to the west side of the mountain.
Oddly enough, most of the seeds that landed in the west were the type that carried the gene for yellow flowers. So when the flowers bloomed in the spring, many were yellow. This was okay with the Stinging Mothers since they could see red or yellow. But the problem was this: the flowers were longer than the ones in the east. It just so happened that there was a genetic trait linked to yellow color that caused the flowers to be long and deep.
In particular, honeybees are the best at finding their way inside. When a honeybee lands on this flower, it immediately notices the guiding lines inside the top petal that point to the base. However, the nectar is not at the base. The weight of the bee on the keel petal triggers the keel to bounce down like a trampoline which forces the petals to spread apart. The stamens inside the keel are covered with pollen. If the bee has pollen from another blossom, it will stick to the pistol and pollinate the flower.
Lipped flowers, such as this sage flower and also members of the pea family, have specialized structures with a lip at the front of the flower that serves as a landing platform. The bee pushes its head into the flower to get to the nectar which is secreted at the back of the flower.
It is very hard for the bee to remove the pollen from this spot. This ensures that the bee carries the pollen from flower to flower for successful pollination.
Plants with small tubular centers, like the Aubrieta, are visited by moths and butterflies. They push their long, thin proboscis into the center of the flower to drink its nectar. Different types of daisies cater to different types of insects. Some daises have hard yellow button-like centers that consist of tiny florets. These flowers are too small for most bees, so they only attract a small number of pollinating insects.
This Inula has small florets that are used as a nectar source by butterflies. Yucca plants and yucca moths share a very intimate relationship with each other. This relationship is particularly important because the yucca plant and its moth cannot survive without each other. The yucca plant can only be pollinated by the yucca moth.
When the female moth is ready to lay eggs, it goes into the yucca flower to collect pollen. The moth then packs the sticky pollen into a ball, sticks it under her head and flies to another yucca flower.
Once she arrives at the second yucca flower, she heads straight to the bottom of the flower to find the ovary. Then, she creates a small hole in the ovary and lays her eggs inside. After the eggs are laid, the female moth scrapes a small amount of pollen from the sticky ball she has placed under her head.
When the eggs hatch, the larvae eat the yucca seeds inside the fruit. The use of insects to disperse seeds is less common than the use of animals for seed dispersal. However, there are some very interesting relationships of plant-insect seed dispersal. Probably the most interesting example of seed dispersal by insects is by the dung beetle pictured left with dung. These little insects are famous for rolling dung until they find a place to bury it and protect it from dung-eating animals.
The dung is eaten later and used for laying eggs. Researchers in South Africa have discovered that the seeds of a plant called Ceratocaryum argenteum mimic a piece of animal dung. These seeds are hard and pungent-smelling, very similar to antelope dung.
The scent and appearance trick the dung beetles into thinking they found animal dung. Dung beetles roll the seed away and help the plant colonize new areas. Other species of plants in South Africa depend on ants for seed dispersal. Ants collect seeds and bring them to their nests. The seeds that are dispersed by ants have small structures, called elaiosomes, on the outer surface that attract ants.
Ants do not harm the seed by eating the elaiosomes. In fact, in some cases the seeds germinate more easily once the elaiosomes are removed by the ants. Other plant seeds are dispersed by beetles, wasps, thrips and some moth species.
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