Trapped Bees and Slap-Shot Gnats – All About Pollinating

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Pollinating062410Mixdown.mp312.37 MB
Chel Anderson is a botanist and plant ecologist for the Minnesota Department of Natural Resources. She lives in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now.
 
Anderson: Hello, Jay.
 
Summer is pretty much in full bloom, so let’s talk about what it is that’s blooming and then, who’s doing the pollinating among the flowers, because I know that’s going on.
 
Anderson: It is summer. We’re just into the real thing now and it really feels like it. The forest and the wetlands are incredibly lush. One can’t drive a road, walk a trail, just walk through the woods, paddle a lake, without seeing things in bloom. So, we’re really now at the point where there’s more things in bloom than aren’t, and that’s an amazing time of year for us, who spend a lot of the year without anything in bloom. There have been tons of wild roses in bloom; I’m sure people have been enjoying those, both the color and the wonderful fragrance. Lots of roadside plants, some native, some not, but yellows and orange hawkweeds; lots of lupines in other places.
 
What about the pollinators? Whose pollinating?
 
Anderson: Another one of the groups of plants that’s very prominent right now are orchids, and I know lots of people are interested in orchids. Orchids are a perfect example of the diversity of form and color and fragrance that the plant world exhibits in its blooming. Hopefully everyone’s familiar with the Showy Ladyslipper, which is our state flower, very robust, pink and white, large orchid. There’s also the Dragon’s Mouth Orchid, which some may be familiar with, pink, white, and frilly yellow on the lip. It grows mostly in open wetlands, a lot of them blooming right in late June, up to the end of June. The twayblades are another group of orchids that are quite common in wet places. Coralroot orchids, these are the orchids that don’t have any green. So, lots of different orchids happening right now.
 
And who are the most prolific pollinators? Obviously these, but are they the only ones?
 
Anderson: No, they’re not, and we have this amazing array of wildflowers, including a wide range of orchids, because only an insect can make a flower. The wide ranging diversity of flowering plants and the wide ranging diversity of insects really coevolved. So, over millions of years, that relationship between flowering plants and insects is what has driven this tremendous diversity that we have, not just here in Minnesota, but around the world. So, everything from moths and butterflies to bumblebees to solitary bees to gnats, mosquitoes, black flies; you know, there’s just an amazing number of insect groups and individual species that are part of this incredible arrangement. The Showy Ladyslipper is very obvious to insects, because of its color. They’re very attractive to bees, so bees will see the flower, go to the flower and, hopefully everyone’s familiar with the pouch, the pink pouch, and there’s an opening in the pouch, and they head for that opening. They go down into it in search for the nectar. They get down in there, and they’re stuck, because they can’t go back out the way they came in because of these in-curled edges on the pouches. So, they get kind of confused, but in some cases there are color lines that they follow and sometimes some long, pointed hairs that they follow that encourage them to go in a particular direction. That leads them to a couple of escape routes. If they pick one or the other of these escape routes, and those escape routes are much narrower, and to get out, they have to go through that escape route. Well, when they first get into the escape route, their thorax, which is where bees would be carrying any pollen from a plant that they previously had visited, their thorax brushes up against the female parts of the flower, and so they deposit that pollen on the stigma, the part of the ovary of the plant that accepts the pollen. And then, as they push further through to get finally out, then they are exposed to the anthers of the plant, and they get dosed with pollen again when they leave. So, when they go to the next flower, they’re carrying that transfer of pollen from one to the next. So, that’s how the cross-pollination happens, that’s how genetic material gets transferred. So, that’s the pay-off for the plants. That’s the Ladyslipper’s style, and they don’t give anything to the insect in this case; it’s a complete ruse. There’s no nectar for the bee, so usually the bees will learn after a time that they’re not getting anything there. But, there’s always no bees to learn, and so they only need to make that error a couple times, and they’ve done their job of moving things around. In the case of the twayblade, this is an orchid at the other end of the size spectrum; an orchid that’s maybe only four inches tall, total. So, an individual flower would be no more than an eighth of an inch. In that little, tiny space, the twayblade orchids are pollinated by a fungus gnat, which is really tiny. So, the fungus gnat comes sailing in there, exploring around, looking for the nectar. There’s a little flap that is kind of covering a hood that sort of covers the important part to the fungus gnat, and so it tries to kind of reach around and get in there, underneath that flap. When it does, it sets off some hair triggers, and that flap then slaps some glue on the face of the fungus gnat. And then, as the fungus gnat is startled and still in a state of, “What happened?” that flap around the flowering parts plasters the pollen all over that glue. These are some really elegant and fantastic in some ways, I mean this is better than science fiction. Right?
 
I was just going to say, it sounds like science fiction. Chel Anderson has been sharing science fiction with us. She’s a DNR botanist and plant ecologist. Thanks for helping us understand smacking fungus gnats.
 
Anderson: You’re very welcome.

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