Well, Now, I Wonder…

People often seem surprised to learn that I’m an introvert – probably because in large groups, I feel pretty comfortable being the center of attention and talking to an interested audience.  However, when I’m just one of many people in a large gathering, I naturally retreat to the edges of the group where I don’t feel hemmed in by humanity.  As a result, during presentations out in the field, I tend to wander and explore while staying within earshot of what’s being said.  I’m not trying to be rude, I’m just keeping my escape routes open…

Accordingly, two of the three mysteries I wanted to share today were things I found while skulking in the background during a tour last Friday at the Valentine National Wildlife Refuge.  The first was a trailing wild bean plant (Strophostyles sp) with a series of intriguing holes in the leaves.  I showed a couple other people, but none of us knew what might have made the holes.  I’m guessing invertebrate, of course, but I don’t have any idea beyond that.  It looks to me like something was rasping away at the surface of the leaf until it punched all the way through and then repeated the process in a new spot.  Anyone recognize this?

Interesting holes in trailing wild bean leaves…

The second mystery relates to some piles of wild rose hip remains scattered around on the ground.  We were standing in the middle of a good patch of wild rose and talking about how plants in recently burned areas (at least this year) seemed to have lots of large fruits.  As I wandered around with my eyes scanning the ground, I spotted several places where some animal had apparently dismantled rose hips, leaving the skin (rind?  husk?) and seeds strewn about on the ground.

Rose hip remains.

At first, I was wondering why an animal would go through the trouble to open up the fruit and then not eat the seeds or skin since there’s not much more to the fruit than that.  Upon a closer look, though, it appears many of the seeds had been split in two, which makes me wonder if something was eating the center of the seeds and then spitting them out – almost like a ballplayer at a baseball game.  I’m guessing this is a small mammal, but don’t remember seeing piles quite like this before.  Help?

A closer look a the rose seeds, which seem to be split in half and hollowed out?

The final mystery was not something I discovered, but instead came from a question someone asked me.  I feel bad, but I honestly don’t remember who it was who asked – I’d give them credit if I did because it was a great question.  The question was, “Why don’t we see big flushes of annual sunflowers in the same place two years in a row, even when there is still plenty of bare ground?”  We’d been talking about the hypothesis that plains sunflower (Helianthus petiolaris) germinates really well when there is abundant bare soil – such as after a fire or drought.  However, the question asker rightly pointed out that it doesn’t seem like the same phenomenon repeats itself in the same location in the following year, even if those bare soil conditions still appear to be present.

Populations of plains sunflower, like the one our group explored in this burned patch of Sandhills prairie, don’t seem to flourish two years in a row, even when bare ground persists. There must be something else driving that population boom and/or restricting a subsequent one.

I don’t have an answer for that sunflower question.  Possible explanations could include 1) the majority of the available seed bank germinated the first year and seeds from that crop need a year or more to become stratified or otherwise prepared to germinate; 2) sunflowers produce chemicals that inhibit their own growth the next year (seems doubtful); 3) an insect, microbe, or other organism builds up large populations during population booms of sunflowers and then either eats or infects seeds/plants of the next generation, preventing them from establishing.  There are probably lots of other possibilities.  Anyone have the answer?

I’ve said it many times, and it’s always true – finding these kinds of mysteries is what helps keep me interested and excited about prairie ecology.  It’s fun to figure out the solution to the mysteries, but then I have to find more mysteries.  Fortunately, there doesn’t seem to be any shortage of them!

Popular Sunflowers

Plains sunflower (Helianthus petiolaris) is an annual plant that responds quickly to bare ground in the Nebraska Sandhills.  They pop up after fire, intensive grazing, pocket gopher activity or something else allows light to hit the soil.  At times, they can be widespread, as they were the year after the 2012 drought. More often, they are found scattered about the prairie in patches of sparse vegetation.  They have started to bloom in earnest over the last couple of weeks, adding beautiful accents to the summer prairie.

Last week, I spent an hour photographing sunflowers and the wide variety of small creatures I found hanging about on them.  In just one hour, I spotted a pretty incredible abundance and diversity of invertebrates within an area smaller than my backyard.  Sunflowers, especially annual sunflowers, are considered by some to be weeds, but these native wildflowers play really important roles in prairie ecology.  Their seeds are extremely valuable as food sources for many wildlife species and their young leaves and flower buds/blossoms are quality forage for other species, including cattle.  During this time of year, the abundant and accessible pollen and nectar of the flowers is what seemed to be attracting the invertebrates I saw.  Here is a selection of photos displaying some of those sunflower visitors.

A variety of grasshopper, katydid, and tree cricket species are all commonly found feeding on the flower parts and pollen of sunflowers.  Weevils, long-horned beetles, and other beetles are also frequently seen.

Weevils and other beetles (including the one at the top right of this photo) were also present on many of the sunflowers I saw.
Hover fly
As a small female bee (Perdita albipennis) was gathering pollen from this sunflower, a male zipped in and began mating with her. She dragged him around and just kept foraging…
Wasps, like this paper wasp, were crawling around the stems and leaves of the sunflowers, apparently gathering extra-floral nectar that was also attracting abundant ants.

The abundance of herbivores, pollinators, and other insects on the flowers and vegetation of the sunflowers seemed to attract a number of predators as well, including robber flies, spiders, and assassin bugs.

A robber fly perches on a flower bud.
A tiny crab spider.
Assassin bug.
It was hard to see for sure, but I’m pretty sure this assassin bug was feeding on an individual of the same Perdita bee species shown above.

I hope these photos, all taken from a small area and within a short time period, help illustrate the kind of resource annual sunflowers can be in the Sandhills.  I’m sure many other wildflowers host similar numbers of invertebrates, but the height and conspicuous nature of sunflowers make it really easy to see and appreciate their value.

Annual sunflowers aren’t aggressive – they just take advantage of open soil and available root space.  As vegetation recovers from whatever event caused it to become sparse, sunflower abundance diminishes…until they get another opportunity to pop back from seeds and make their contribution to the prairie ecosystem.

Photo of the Week – August 18, 2016

There is an unmistakable look to late summer prairies, and that look is YELLOW.  Sunflowers, goldenrods, and Silphiums (compass plant, cup plant, rosinweed) are all front and center this time of year.  The visual dominance of yellow flowers is obvious as I look back through some of my favorite prairie photos from this week.

Cup plant in restored tallgrass prairie at Deep Well Wildlife Management Area west of Aurora, Nebraska.
Cup plant (Silphium perfoliatum) in restored tallgrass prairie at Deep Well Wildlife Management Area west of Aurora, Nebraska.
A black blister beetle and another small beetle feed on the same Missouri goldenrod flower head.
A black blister beetle and another small beetle feed on the same Missouri goldenrod flower head.
Stiff sunflower (Helianthus pauciflorus).
Stiff sunflower (Helianthus pauciflorus).
Compass plant.
Compass plant (Silphium laciniatum).
Rosinweed (Silphium integrifolium).
Rosinweed (Silphium integrifolium).
During yellow season, anything that's not yellow really stands out - especially when it's tall and BLUE. Pitcher sage (Salvia azurea).
During yellow season, anything that’s not yellow really stands out – especially when it’s tall and BLUE. Pitcher sage (Salvia azurea).

I wonder if anyone has gone through all the prairie flower species to see which color is most common (I’ll be someone has).  It has to be yellow, doesn’t it?  Purple, pink, and white are in the running, but I bet yellow wins pretty easily.

No complaints here.

Photo of the Week – December 4, 2015

We had a winter storm pass through our area at the tail end of the Thanksgiving weekend.  After a light coating of ice, we got a couple inches of fluffy snow.  Monday was a gloomy overcast day – too dark to inspire me to venture out with my camera.  However, Tuesday morning began with a beautiful sunrise and calm winds.  A fantastic opportunity for winter prairie photography.   Unfortunately, I had to enjoy the light from the interstate as I drove to a meeting.  Wednesday was another great sunrise and morning of light, but I was on the road again – heading to a different meeting.  Yesterday, most of the snow melted and, just like that, the first snow of the year was gone.  Not a single photograph taken…

So, instead of posting a beautiful photo of fluffy snow on the prairie today, I’m reaching back to a photo from August.

Stiff sunflower (Helianthus pauciflorus) Lincoln Creek Prairie, Aurora, Nebraska.
Stiff sunflower (Helianthus pauciflorus) Lincoln Creek Prairie, Aurora, Nebraska.  Click on the image to see a larger version – and maybe the hidden visitor on it.

I like this photo of a stiff sunflower for several reasons, including the interesting shapes of the ray flowers (“petals”) that are not yet fully extended.  However, I also like the photo because there is a hidden visitor on the flower that I didn’t see until well after I took the photo.  Can you see it?

Here is a cropped version of the image to give you a better look.

Stiff sunflower (Helianthus pauciflorus) Lincoln Creek Prairie, Aurora, Nebraska.
Can you see the tiny larva feeding on pollen?

I don’t know what this little larva will grow into, but it appears to be feeding on pollen and stringing lines of silk between anthers as it moves.  I featured a similar larva in an earlier post that showed a sunflower which had been “sewed shut” by silk – probably as a protective measure to allow the larva to feed on the flower under cover.  I wonder if this larva will follow the same procedure as it gets bigger and can’t hide as easily out in the open.

Interestingly, the photos from that earlier post featuring the “seamstress larva” were taken on the same day as the photo in this post.  In fact, I took the photo of the tiny larva just a few minutes after photographing the sewed-up flower.  You’d think I’d have been on the lookout for larvae on sunflowers, but I still missed it, even through my macro lens.  Then, I missed it again as I worked up the photo later, even as I was looking closely at it on the computer to adjust sharpness, etc.  I guess that’s a testament to the effectiveness of the hiding strategy of this little larva!

I hope its camouflage allowed the little larva to grow up, pupate, and have lots of offspring to carry on its strategy.  I bet it did.

Photo of the Week – September 10, 2015

A few weeks ago, I took my camera across town for a walk in a small local prairie.  There were numerous flowers blooming, but the stiff sunflowers (Helianthus pauciflorus) were stealing the show.  I shot quite a few photos of them from various angles.

Hover fly on Stiff sunflower (Helianthus pauciflorus) Lincoln Creek Prairie, Aurora, Nebraska.
This little hover fly was enjoying a meal of stiff sunflower pollen.  Lincoln Creek Prairie, Aurora, Nebraska.
Stiff sunflower (Helianthus pauciflorus) Lincoln Creek Prairie, Aurora, Nebraska.
The sunflower perspective.

I noticed that a few sunflowers seemed to have their “petals” (technically speaking, they are the ray flowers) folded in toward the center of the flower.  I’d seen this quite a few times before, but this time I decided to investigate.  I gently pulled the petals apart and found they’d be held down with what appeared to be silk.  Beneath them, an insect larva was hiding and, presumably, feeding on pollen or other flower parts.

Caterpillar in Stiff sunflower (Helianthus pauciflorus) Lincoln Creek Prairie, Aurora, Nebraska.
A closed-up stiff sunflower.
Caterpillar in Stiff sunflower (Helianthus pauciflorus) Lincoln Creek Prairie, Aurora, Nebraska.
The larva revealed.  Note the remnants of silk and the anthers still sticking to the petal after I pulled everything apart.
Caterpillar in Stiff sunflower (Helianthus pauciflorus) Lincoln Creek Prairie, Aurora, Nebraska.
A close up of the caterpillar (?)

I’m not expert enough with insect larva identification to know for sure, but I’m guessing the larva is a moth larva – I know at least some of those have the ability to make silk.  Some of you reading this will surely know more about them and comment below.  (Thanks for your help.)

A few days later, I ran across some similarly closed up flowers in a different prairie.  When I opened those up, there was another larva inside, but it was much darker in color.  I wonder how many different species have this behavior?

The larva I found was just one of many examples of insects that create safe hiding places for their young to feed in.  Spittle bugs and gall-forming insects are two others that are common in prairies.  Of course, for every great hiding strategy, there is at least one predator that has developed a counter strategy.  I don’t know what eats the petal-tying larvae, but I bet there’s something out there.  I’m pretty sure guys-with-cameras are not the only ones who can find them.  Fortunately, for the larva I found, I wasn’t hungry at the time.

 

Double flowered sunflowers

When you look at a sunflower, you’re really looking at a composite of tiny flowers, or florets.  The same is true for asters, daisies, and other members of the composite family of plants.  The colorful “petals” of a sunflower are actually a series of tiny florets, called ray flowers, and the seed-producing dark center is made up of lots of disk flowers.  Together, they join together and function as one large flower that attracts pollinators and produces seed.

Stiff sunflower.  The Nature Conservancy's Platte River Prairies, Nebraska.
This sunflower has two kinds of flowers – ray flowers that look like yellow petals, and small disk flowers in the center.

This is how sunflowers are “supposed” to look.  However, you will occasionally find a sunflower that looks more like a chysanthemum, with yellow ray flowers across most or all of the face of the flower head.  Botanically speaking, this is called “double flowering”.  Horticulturists find and breed double flowering varieties of sunflowers and other composites, and you can find them at many nurseries and other plant stores.

Maximilian sunflower.  TNC Bluestem Prairie, Minnesota.
A double flowered Maximilian sunflower (Helianthus maximiliani) at The Nature Conservancy’s Bluestem Prairie in Minnesota.  Most of the disk flowers have been replaced by ray flowers.

When we were in Minnesota a few weeks ago, we saw a fair number of double flowered Maximilian sunflowers at The Nature Conservancy’s Bluestem Prairie.  I don’t remember seeing so many examples in one prairie before, but maybe I just haven’t paid close attention.  The abundance of them made me curious to learn more, so I did a quick internet search when we got back to Nebraska, and emailed a few botanist friends for more information.  The best information I found was related to a 2012 PLos Genetics journal article in which scientists described their discovery of the particular mutation that causes double flowering to occur.  You can read descriptions of the research here and here.

Maximilian sunflower.  TNC Bluestem Prairie, Minnesota.
Extra “petals” can be awfully pretty.

You might think of genetic mutation as something bad, but mutations are actually very common and mostly benign (and don’t affect form or function).  Now and then, a mutation can cause serious problems for an organism, but other times it can generate variations in a DNA sequence that turn out to be advantageous.  Double flowering seems to be somewhere in the middle.  On one hand, producing fewer disk flowers means the plant has fewer opportunities for pollination and seed production.  On the other hand, extra ray flowers could make a plant more attractive to insect pollinators and increase visitation.  In the case of the Maximilian sunflowers at Bluestem Prairie, the mutation doesn’t seem too disastrous, at least based on the number of plants we saw that have the trait.

I’m glad – it sure is pretty.

Photo of the Week – January 23, 2015

There are a few subjects I can’t seem to keep from photographing.  Milkweed seeds, for example.  Patterns of ice on frozen wetlands.  Dew-covered insects.  And sunflowers.

What flower is more distinctive?  Their bright yellow color and big round flowers stand out, even in the most showy of flowery prairies.  Insects seem to find stiff sunflower attractive too, based on the number of insects I’ve found and photographed on them.

Plains sunflower (Helianthus petiolaris) in restored sand prairie.  The Nature Conservancy's Platte River Prairies, Nebraska.
Plains sunflower (Helianthus petiolaris) in restored sand prairie. The Nature Conservancy’s Platte River Prairies, Nebraska.

We’re fortunate to have seven different species of sunflower in our Platte River Prairies, five of which are perennials.  The above photo is of one of the two annuals, plains sunflower, which inhabits the drier sandy uplands of our sites and is very abundant in the Nebraska Sandhills to our north.

I have plenty of sunflower photos I like, but this is one of my favorites from last year.  I like the overall composition, but I also like that the sunflower in the foreground is atypical.  Something has prevented the petals (ray florets, for you botanists) from developing completely.  It’s interesting (and not unattractive), and also stimulates questions about what happened, and why.

I like mysteries…

Wanna Know What Really Makes A Sunflower Lose its Head?

Nearly-decapitated sunflower heads, scattered across the prairie.  Oh, the devastation!  Who could be carrying out such an evil plan?

(Ok, more accurately, a weevil plan?)

Weevil damage
I found this sad-looking stiff sunflower (Helianthus pauciflorus) during a prairie hike back in August.
Maximilian
Stiff sunflower was not the only species being targeted.  Maximilian sunflowers (Helianthus maximiliani) were also dangling…   This photo was taken just a few minutes after the first.

The head-clipping weevil, aka the Silphium weevil (Haplorhynchites aeneus) is a small dark-colored weevil, less than a centimeter in length.  Females girdle the stems beneath sunflower heads – as well as other plants such as compass plant and rosinweed – so that the flower head falls over, but usually doesn’t drop completely off, at least not right away.  Once a flower has been knocked over, other weevils usually show up – male and female – to feed on pollen, mate, and lay eggs in the blossom.

Doing some research for this post, it was hard for me to confirm what happens next, but it seems the eggs usually don’t hatch until the flower eventually falls to the ground.  The larvae feed on the decomposing flower head and then burrow into the earth to overwinter.  It is thought that clipping the flower before laying eggs on it might make the flower a less attractive place for other insects to lay eggs, saving more food for the weevil larvae.

I have rarely seen the head-clipping weevil itself, and had never photographed it.  On the day I photographed the sunflowers shown above, though, I finally saw one fly off a stem and managed to get a documentary photo of it.  Look at all the sunflower pollen stuck to it!
Before that August hike, I hadrarely seen the head-clipping weevil itself, and had never photographed it. Not long after looking at the sunflowers shown above, I finally saw a weevil fly off and managed to get a documentary photo of it when it landed. Look at all the sunflower pollen stuck to it!

The clipping behavior by weevils can cause problems for those raising sunflowers commercially, but I’ve never seen it impact enough flowers to cause any serious issues in prairies.  I’m guessing that some of you readers will know much more about the head-clipping weevil than I do, and I hope you’ll contribute additional information in the comments section below.  Thanks in advance!

So, to summarize the weevil plan:  The weevil female nearly decapitates a flower and then mates with weevil males and lays weevil eggs right on the mortally wounded blossom.  The weevil babies eat the dying flower and then burrow into the ground until the next spring.  Then they make a triumphant return and hatch their weevil plans once again.  And who do we have to thank for finding out about all of this?

Weevil scientists, of course!

Photo of the Week – September 25, 2014

Dufourea
A small male bee (Dufourea marginata) waits hopefully for a female to come by his sunflower.  The Nature Conservancy’s Platte River Prairies, Nebraska.

Some people have the mistaken impression that I know a lot about bees.  Those who know me better understand that while I have a decent understanding of the ecology of bees and other pollinators, my identification skills are very rudimentary.  Fortunately, I have become friends with Mike Arduser, formerly with the Missouri Department of Conservation, who has a comprehensive knowledge of bees in the Central United States.  I sent Mike these photos a couple weeks ago and he generously identified the bee species for me, and provided a little background information as well.

The elongated mouthparts help identify this as a member of the genus Dufourea.  (But you probably already knew that.)
Mike says the elongated mouthparts help identify this as a member of the genus Dufourea. (You probably already knew that.)

According to Mike, the bee species I photographed on stiff sunflower (Helianthus pauciflorus) is a specialist feeder on sunflowers.  It’s a common late summer bee in the Great Plains, but rare further east in the tallgrass prairies of Missouri, Illinois, etc.  The bee nests in the ground and seeks out sunflowers for pollen and nectar.

Another male.
Another male.

During the morning when I photographed this species, I saw quite a few different bees.  Most of them were males, and didn’t seem to be feeding on sunflowers as much as just hanging around the edges of the flowers – apparently waiting for a female to stop by.

I almost always embarrass myself when I go out on a limb with bee identification, but this bee looks like a female to me.  Look at how much fuzzier the rear legs are - a common sign of females because those hairs help store and transport pollen back to the nest.  The bees in the other three photos above don't appear to have the same kind of fuzzy legs.  (Ok, now Mike or someone else can tell me how wrong I am.)
I almost always embarrass myself when I go out on a limb with bee identification, but this bee looks like a female to me. Look at how much fuzzier the rear legs are – a common sign of females because those hairs help store and transport pollen back to the nest. The bees in the other three photos above don’t appear to have the same kind of fuzzy legs. (Ok, now Mike or someone else can tell me how wrong I am.)

I’ve only been learning about bees for a few years now.  It’s amazing how many different species – and behaviors – I see, now that I’m looking for them.  Before sending the photos to Mike, I was able to recognize these bees as being in (likely) the same species, and figured most of the ones I was seeing were males, based on their behavior.  I still have much to learn, but paying attention to bees has certainly changed the way I see our prairies.  As I wrote last fall, I’m definitely looking at our prairies through “bee goggles.”  We’re not managing our prairie exclusively for bees, but they definitely factor in to our management decisions – not just because they are important themselves, but because promoting quality bee habitat is a great way to help ensure quality habitat for many other species as well.

Photo of the Week – December 5, 2013

Continuing the theme from earlier this week, here is another photo of a sunflower seed head.  This one was taken on a frosty morning last week.

A sunflower seed head
A Maximilian sunflower seed head.  Deep Well Wildlife Management Area, Nebraska.

I usually try to avoid putting a horizon line behind the subject of a close-up photo because it can add unnecessary distraction to the image.  In this case, however, I tried the photo both ways and decided I liked the one with the horizon better because it gave the image some additional context and depth.

Here’s the alternate version – see what you think.

The same sunflower head shown above from a slightly different angle to keep the horizon line out of the image.
The same sunflower head shown above, but from a slightly different angle to keep the horizon line out of the image.