Thanksgiving is a time to gather with loved ones and usually involves first preparing and then ingesting a lot of delicious goodies. Each family has recipes and traditions related to Thanksgiving, and even foreigners (like myself) may join in and create new traditions. Independently of who we are and our origin, the meals we prepare include a number of common foods: cranberries, pumpkins, sweet potatoes, pecans, and potatoes.
For this year’s Thanksgiving, I want to take us on a trip to recognize and thank nature and some of our little winged friends, without whom we would not be sharing all that deliciousness with our loved ones. Plus, after reading this you will know some cool fun facts you can share with others during your Thanksgiving meal!
Cranberries are the fruits of a plant closely related to blueberries and huckleberries, which all are native to North America. Like blueberries and huckleberries, cranberries need pollinators to produce fruit. The reproductive organs (anthers – where pollen is produced, and carpels – where the ovules are hosted) in a cranberry flower mature at different times, which means that a flower can’t self-pollinate and needs a pollen vector to produce fruit.
As you may know, no pollination means no fruits, and no fruits means no cranberry sauce. Luckily, nature provides and pollinators are around! We know today that several different bees visit cranberry flowers, with bumblebees being some of the best pollinators. Some other wild bees (for example, mining bees, Andrena) also contribute to the pollination of this plant, and honeybees can pollinate as well but not as efficiently as bumblebees and other native bees.
Pumpkins, squashes, and zucchini are all closely related vegetables that also require pollinators to produce fruit. Unlike cranberries, pumpkin plants produce separate and distinct female and male flowers. Because in these plants the female and male reproductive organs are physically in different parts of the plant, pollination (and thus fruit production) requires a pollen vector. Again, we would have no pumpkin pie if our pollinator friends were not around!
So, who pollinates pumpkins? Pumpkins have very specialized pollinators that do the best job at pollinating. In the US, this specialized pollinator is the squash bee Peponapis, which feeds their larvae a strict diet of squash pollen. Furthermore, unlike many other bees, both the males and females of the squash bee pollinate, since mating happens in the flower. Even though the squash bees are by far the best pollinators of pumpkins, other bees (including honeybees) can occasionally visit and pollinate the flowers… but really it’s these little cuties that we need to thank for all the delicious pumpkin!
Like pumpkins, pecan plants can’t automatically self-pollinate and need a pollen vector to produce the yummy nuts we eat. This is not only because their female and male flowers are separated spatially on the plant (like they are for pumpkins); they also flower at different times of the year on the same plant.
To be pollinated, the female flowers of a pecan plant need to receive pollen from the male flowers of another plant which is flowering at the same time. For this reason, pecan flowers need a vector of pollination, which here is not an insect but the wind! Pecan flowers are indeed adapted to wind pollination, displaying hanging bunches that shake with the wind, releasing and catching a lot of the pollen in the air.
The part of the sweet potato plant that we eat during Thanksgiving is the tubers, which are roots. And since what we eat is not a fruit, pollinators have no role to play for this Thanksgiving ingredient… at least not directly. But the sweet potato plant still needs pollinators to produce seed and breed, because their flowers are unable to be successfully pollinated by the same flower’s pollen.
Pollinators are then really important for the successful maintenance of the genetic diversity of this plant. Sweet potatoes belong to the morning glory family, and as its name suggests, flower in the morning hours. They are pollinated by many different types of bees (from large bumblebees and carpenter bees to smaller bees such as sweat bees), which visit the flowers for nectar and pollen.
As for sweet potatoes, the part of the potato plant we eat is not the fruits but the tubers. Pollinators are not needed for obtaining these tubers, but the plant requires pollinators to be able to breed and maintain genetic diversity. Since they are in the same family (the nightshades), potato flowers look similar to those of tomatoes and eggplants.
Like in those other vegetables, pollinator visits, and more specifically something called ‘buzz pollination,’ needs to occur for successful pollination. In this type of pollination, the insect visits the flower and buzzes loudly, which shakes the flower, releasing the pollen, which they then transfer to a different flower during their next visits. Among these buzzy bees, bumblebees and mining bees (Andrena) are very efficient at pollinating potatoes.
[VIDEO: Buzz pollination of a bumblebee on a potato flower. Note how the pollen is released from the anthers — the four yellow long organs — and sticks to the bee abdomen where the stigma — the female flower organ in the middle of the flower — rubs the bee abdomen where it collects the pollen and gets pollinated. Video by thyreodon.]
By Anahí Espíndola, Assistant Professor, Department of Entomology, University of Maryland, College Park