Hubbard Fellowship Blog – Lobelias and Pollinators

A guest post by Anne Stine, one of our Hubbard Fellows.  All photos are by Anne.

Derr Sandpit Wetland Restoration - The Nature Conservancy's Platte River Prairies, Nebraska.

Derr Sandpit Wetland Restoration – The Nature Conservancy’s Platte River Prairies, Nebraska.  September 12, 2013

I was scouting for native seeds in our sand pit restoration across from the crew quarters when I noticed a fascinating pollinator-plant interaction. This activity would’ve been best captured on video with a high quality zoom (which I did not have), but I was able to take pictures.  Bumble bees, and only bumble bees, were fighting their way into great blue lobelias along the edge of our restoration.  Meanwhile, their neighboring cardinal flowers were visited by butterflies exclusively.  Why, and how, were these two closely related flowers so specialized with their pollinator partnerships?

First, let’s consider the great blue lobelia (Lobelia siphilitica).  The architecture of this flower insures that only burly bumble bees can gain access to the pollen and nectar.  Some other insects “cheat” and chew holes in the flower to by-pass the petal-gate, but bumble bees are their primary visitors. Watching the bumble bees pry open the flowers was entertaining. First, they climb onto the flower’s extending ‘tongue’. Then, they push aside the two top petal ‘lips’ and dunk themselves head first into the flower.  Their front half is completely inside the blossom. Only their bottoms and back legs stick out.  They clamber up the stalk, climbing from flower to flower until they reach the top, and then they fly off to visit a neighboring plant.  Because great blue lobelia seems to grow in patches, this is an efficient operation for both bee and blossom.  The bees act drunk on nectar, and the flowers are practically guaranteed a thorough pollination.

Ghh

How bumblebees gain entry to lobelia flowers.

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Success!

Success!

Conversely, cardinal flower (Lobelia cardinalis) is traditionally considered to be a ‘hummingbird-specialist’ plant.  We are just outside the range of the ruby throated hummingbird here on the Platte River Prairies.  Instead, butterflies with their long tongues seem to have taken over the majority of the nectaring and pollination duties.  Or perhaps cardinal flowers in this part of Nebraska predominately self-pollinate.  At any rate, bees weren’t the major customers on cardinal flowers.  Cardinal flowers were visited by butterflies.

How strange that these two wetland con-generics, great blue lobelia and cardinal flower, could grow in intermingled patches and still rely on totally distinct pollinator communities.  Nature is weird and wonderful.

This monarch had the choice between blue lobelia and cardinal flower.  She chose cardinal flower. So did all the other butterflies.

This monarch had the choice between blue lobelia and cardinal flower.  She chose cardinal flower. So did all the other butterflies.

This monarch had the choice between blue lobelia and cardinal flower. She chose cardinal flower. So did all the other butterflies.

Photo of the Week – September 20, 2012

Last week, I managed to find about half an hour’s time to wander with my camera, so I decided to try to get some more photos of this year’s drought impacts.  I headed down toward one of our crispy brown lowland prairies, with every intention of photographing dormant grasses and wildflowers.  However, there’s a wetland swale in that prairie that has stayed wet enough during this summer that the vegetation is still vibrant, green, and blooming.  Despite my best efforts, I found myself edging toward the swale…

There were several wildflower species blooming in the swale, with lots of bees and soldier beetles crawling around on them.  But the visual standouts were the lobelias.  Both cardinal flower and blue lobelia were tall and in full flower, so I spent a few minutes taking their portraits.  It’s hard to imagine a more striking flower than a bright red cardinal flower, but the counterpoint of the blue lobelias was every bit as pleasant to look at. 

Cardinal flower (Lobelia cardinalis). Platte River Prairies, Nebraska.

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Blue lobelia (Lobelia siphilitica).

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I didn’t end up with a camera full brown grass images, but in a way, these lobelia photos are equally representative of this year’s drought.  Although the majority of the landscape is dead and brown, there are bright spots of green scattered around in places where the soil organic matter is high enough to hold moisture, or where groundwater is still close enough to the surface to support life.  Those scattered oases of green are keeping a number of insects and other species alive at the moment, as demonstrated by the loud buzzing sound that surrounded me as I walked through the wetland swale.  Besides being a good “glass half full” thing to do, focusing on those oases in times of drought is probably a critical conservation strategy.  Those little patches of life are making huge contributions to the ecological resilience of our larger prairie/wetland ecosystem, and we should be studying the conditions that create them and thinking about how to ensure those conditions are sustained. 

Plus, the flowers are really pretty.