I walked around one of our newer prairie/wetland restoration sites yesterday morning. The sun was just starting to punch some holes in low-lying fog and everything was wet. A cool and wet summer morning is usually a great time to find immobile insects and photograph them, but I for some reason I wasn’t seeing much as I walked. Not a dragonfly, not a butterfly, not even a big ol’ beetle… I did eventually find some bees encased in dew drops, waiting for the sun to emerge to warm and dry them.
Unlike females, male solitary bees don’t have nests to defend and spend most of their days chasing around foraging females. When night comes, most species (except for a few night-feeding bees) just find a convenient place to shelter until morning. Many times, they seem to choose roost sites where they can be a little protected from potential predators, but other times they just end up on the exposed surface of a flower (the equivalent of falling asleep on their dinner plate, I guess). Most of the bees I saw yesterday were at least somewhat hidden- which is why I had to look pretty hard to find them, but there were a few out in the open as well, including the one pictured below.
As I wandered along a wetland swale, I was admiring one of my favorite plants – prairie gentian (Eustoma grandiflorum) – when I happened to look down inside the blossom and spotted a fuzzy little bee. Because it seemed like a convenient and relatively safe hiding place for bees, I started looking into other flowers too, and sure enough, I found more bees.
All the bees I was seeing in the prairie gentian flowers looked like the same species to me, but I’ve become smart enough not to overestimate my ability to tell bee species apart, so I double checked with Mike Arduser. Mike confirmed that they are all male agile long-horned bees (Melissodes agilis), as was the bee I’d seen on the rosinweed flower. He said they appear to have just recently emerged, based on their fresh appearance. I’ll take his word for that and so should you.
Mike also confirmed that the agile long-horned bees don’t have any particular tie to prairie gentian (they don’t specialize on its pollen or use it for nesting sites or materials). Instead, it just appears a number of them independently recognized the potential value of prairie gentian flowers as safe overnight roost sites. If I hadn’t been specifically admiring the gentian flowers, I’m sure I wouldn’t have noticed the bees. I’m guessing most predators wouldn’t have spotted them either, though if a smart predator had happened to find one then and decided to do what I did and check other flowers nearby, it would have had a pretty easy time filling up on bees for breakfast!
After hearing from Mike, I followed up with a series of questions I’m guessing even he can’t answer. Among those, I’m wondering if an individual bee returns to the same roost site night after night – assuming it isn’t disturbed while sleeping the previous night. If that hasn’t been studied, it seems like it would be relatively easy to do a mark and recapture study on them. The trick might be to catch the bees AFTER they leave their roost, though, so they don’t associate that roost site with being caught… Ok, maybe it wouldn’t be as easy as I was thinking. If you try it, however, let me know what you figure out!
Most of what we read in the news about declines in bee populations focus on (non-native) honey bees. Yes, those populations are suffering declines from the combined impacts diseases, habitat loss, pesticide use and other factors. However, there are nearly 4,000 bee species in North America, and many of them are dealing with the same pressures and threats as honey bees. In addition, honey bees are social insects, living in large collaborative colonies of workers and queens. The vast majority of bees in North America, however, are not social, and they succeed or fail on the backs of single moms.
Solitary bees – bees that don’t live in colonies – are all around us, but they go largely unnoticed. Many escape our attention because of their small size, but others are as big as or bigger than honey bees. Solitary bees can vary greatly in their diet preferences. Some are generalists, feeding on nectar and pollen from a wide variety of flower species. Others have much more narrow diets, feeding only from sunflowers, for example, or other categories of flowering plants.
Most solitary bees in prairies live in underground burrows, though others live in hollow plant stems or similar spaces. In colonies of social bees, the work of gathering food, maintaining and defending the home, and feeding and caring for the kids is split between hundreds or thousands of bees. In the case of solitary bees, the single mom does everything. In most cases, she finds a likely spot, digs a burrow and prepares it for eggs. Then, she flies around the neighborhood in search of the kinds of flowers she can collect food from. As she nears the flowers, she’s likely to encounter males of her species, who basically spend their entire lives buzzing from flower to flower, hoping to find females to mate with.
Assuming the single mom can find food nearby, she returns from foraging with a load of pollen and nectar, which she combines into a ball of sticky dough. She places that in a cell within her burrow, lays an egg on or next to it, and seals up the cell. Then, she takes off to repeat the process: find food, mix it together, lay an egg with it, seal up the cell. Later, the eggs will hatch, and the larvae will stay in their cells and feed on the dough balls provided for them until they grow into adults and leave the nest.
As you might imagine, life isn’t easy for single mom bees. They have to gather food for themselves and their kids, while fighting off overly-enthusiastic males with only one thing on their minds. When they aren’t out finding food, they are building and provisioning baby rooms or sitting vigilantly at the entrance of the burrow, defending it from marauding wasps or other threats. After mother bees have filled their burrow with eggs-in-cells, they seal up the whole nest and fly away, hoping for the best.
Single mom solitary bees have difficult lives, but there are ways we can help them. First, we can help ensure the availability of nesting sites. Some ground-nesting bees need areas of bare ground, and many others need at least access to the soil without having to fight through a dense layer of plant litter. Similarly, stem nesters would appreciate it if you didn’t chop down all of last year’s plant skeletons, especially those of raspberry, sunflower, rose, leadplant, and other plants with hollow stems. Providing this kind of nesting habitat is important in prairies and other natural areas, but also in backyard gardens and other urban areas. Because solitary bees aren’t aggressive toward humans, there’s no downside to sharing your yard or garden with them (and, as pollinators, they’ll work for their housing).
Perhaps more importantly than housing, what bees need most is food. The key to supporting strong bee communities is plant diversity. A prairie or garden with lots of different kinds of flowers will support lots of different kinds of bees. Specialist bees will be able to find the particular flowers they need, and generalist bees won’t run out of food when one kind of flower stops blooming, gets eaten by insects, or is wiped out by disease. Early spring can be a particularly difficult time for bees to find food because of the relative scarcity of flowers at that time of year. Boosting the spring-time abundance of both native wildflowers and flowering shrubs in gardens and natural areas can be very helpful.
In prairies and other large-scale habitats, it’s important to think about the flight range of bees. Honey bees can travel up to several miles to find food. Most solitary bees are considerably smaller, however, and they may be limited to a range of a few hundred yards or less from their nest. During their nesting season, bees will need to find everything they need to survive and supply their nests from that relatively small circle of habitat. The availability of abundant flowers of many kinds within that circle helps ensure that bees can find food throughout the season. If a large area surrounding a bee’s nest is mowed or grazed intensively, it is left stranded with a nest in the middle of a food desert.
If you’re a landowner or land manager, think about your property from the perspective of a single mom bee. Pick a few spots on your land and visit them every few weeks to see what the abundance and diversity of flowers looks like. If a bee was nesting where you stand, could she find what she needs for food within a short distance of that location? Are there times of year when it’s hard to find abundant flowers? If so, can you tweak your management or implement restoration strategies to make more flowers available? Are there places where bees can find bare soil for nesting, or is there a layer of thatch covering the soil across your whole site? Burning, intensively grazing, or haying portions of your land each year can help reduce thatchiness and help ensure bees’ access to soil. However, creating patches of prairie habitat representing a full spectrum of vegetation structure types (tall/dense, short/sparse, mixed-height, etc.) will be of maximum benefit to both bees and other insect and wildlife species.
Single mom bees deserve our respect and admiration. They build and prepare their nest, seek out and harvest food while dodging predators and lustful males, and provision their eggs with food and a safe place to grow up. Oh, and along the way, they also pollinate and help ensure the survival of the majority of plants on earth. It seems only fair that we should acknowledge their work and do what we can to help them out.
While the vast majority of native bees are solitary bees, some are social as well, including bumble bees, some sweat bees, and others. Bumble bees, in particular, are very important pollinators because of their size and mobility as well as their willingness to visit many different kinds of flowers. As opposed to honey bees, whose colonies can survive the winter intact, all bumblebee individuals except fertilized queens die at the end of the growing season. Those fertilized queens overwinter and then become single moms in the spring. Once the queen’s first brood matures, those bees take over the foraging work and take care of the queen. You can learn much more about solitary bees and other native bees here.
Many thanks to Mike Arduser and Jennifer Hopwood for reviewing this post for accuracy. Any remaining errors are mine, not theirs.
Because conservation work can sometimes seem like blowing into the wind, it’s important to pause periodically to celebrate progress. For example, I am really excited about what has been accomplished in the field of prairie restoration. We’ve known for a while that we can convert cropland to prairie vegetation with a high diversity of plant species (150 or more species per planting), and that we can do that on a scale of thousands of acres. The Nature Conservancy has large projects in states like Indiana, Illinois, and Minnesota where restored prairie landscapes now range from about 5,000 to 20,000 acres in size. The U.S. Forest Service is transforming an old U.S. Army Arsenal into 20,000 acres of prairie in Illinois. Prairie Plains Resource Institute, the organization that pioneered restoration techniques in Nebraska, is planting up to 1000 acres a year now and has established well over 10,000 acres total across the state.
Here in our Platte River Prairies, we’ve restored more than 1,500 acres of cropland to prairie. That’s not insignificant, but more importantly, we’ve been testing the idea that those restored prairies can help defragment the ecological landscape around them. Habitat fragmentation is one of the largest threats to today’s prairies because it shrinks and isolates populations of species, making them vulnerable to becoming locally extinct without the chance of recolonization from nearby sites. The real promise of prairie restoration is that it can enlarge and reconnect scattered remnants of native prairie, providing populations of animals and plants a much better opportunity to survive and thrive. It’s not feasible or desirable to convert the majority of cropland in the central North America back to prairie, but there are particular sites where strategic restoration work could make a huge difference in the potential survival of prairie species and ecological services.
In order for prairie restoration to help defragment landscapes, restored prairies have to provide suitable habitat for the species living in small isolated prairies. Many bees and other insects specialize on certain plant species, for example, and other animals rely upon an abundance of prey, a diversity of seeds, or other particular food or habitat conditions. Satisfying the individual needs of all those prairie animals is a critical measure of success if prairie restoration is going to successfully stitch isolated prairies back together.
Over the last several years, we’ve been collecting data to see whether the species of bees, small mammals, grasshoppers, and ants in our unplowed prairie remnants have moved into adjacent restored habitat. The results have been very positive. While not every species of animal living in our remnant prairies has been found in nearby restored habitat, we’ve found the vast majority of those we’ve looked for. We suspect that most of the remaining species are also present but that our limited sampling effort just hasn’t yet picked them up. We’ll keep trying.
These results mean that where prairie landscapes have been largely converted to row crops, we don’t have to just watch while insect or small mammal populations careen toward local extinction in tiny isolated prairies. We’ve shown that we can make those prairies larger and more connected, and that animal populations can grow and use new restored habitat and diverse plant communities. We’ve also shown that restored prairies can sustain their biological diversity for decades, even through periods of intensive grazing and drought. While there are still plenty of questions and potential improvements we can make, we’re now at the point where society needs to decide whether and where to do this kind of restoration.
I don’t know about you, but I think that’s pretty exciting!
Nebraska and other states in central North America have large swaths of productive and important cropland. As I said earlier, I’m not advocating that we convert most of that back to prairie. However, there are specific sites where row crop agriculture is marginally productive/profitable and the long-term interests of both society and local landowners might be best served by putting land back into diverse and productive grassland. Agricultural policies and subsidy programs will obviously play a huge role in this kind of strategic large-scale restoration, and getting the policies in place to facilitate this kind of common sense restoration will be plenty difficult. That’s nothing new, however. What’s new is our confidence that if we can implement targeted restoration work, it can make a real difference to prairie conservation.
Restoring the viability of prairies in fragmented landscapes is critically important to prairie conservation success. The challenges of conserving species in small isolated prairies are immense, and many of those prairies will continue to see declines in biological diversity and ecological function over time unless we can make them bigger and more connected with other prairies. Helping to document our ability to do that – at least for many prairie species – has been one of the most satisfying things I’ve done during my career.
Important footnote: Restored prairies are not the same as remnant unplowed prairies. Soil organic matter levels, for example, can take many decades to recover from tillage, and relationships between plant and microbial communities may take just as long to become reestablished. Our success in prairie restoration should definitely not be used as justification for plowing up remnant prairie! However, it’s equally true that prairie restoration efforts aren’t failures just because they can’t create an exact replica of prairie as it existed before it was converted to farmland. If defragmenting prairie landscapes is the primary goal of restoration, we just need to create restored prairies that complement – not copy – remnant prairies.
Pollinator populations are in trouble for a lot of reasons. Loss and degradation of habitat, pesticides, and diseases are all major contributors. However, at least in the Central United States, much of the pollinator decline can be tied to spiny pink/purple-flowered plants and the way humans react to them.
On the face of it, thistles seem like they’d be pretty well-liked. Thistle seeds are a major food source for birds and other wildlife, as well as for a variety of invertebrates. The abundant nectar and pollen found in thistle flowers make them one of the most popular plants among both pollinator and non-pollinator invertebrates. As if that wasn’t enough, most thistles have large and/or abundant blossoms, which you’d think would make them very attractive to people. Sure, they’ve got spines, but so do cacti, yucca, and many other plants gardeners love to landscape with. So why do we hate thistles so much?
The cultural dislike of thistles is not at all a new phenomenon; references to the unpopularity of thistles can be found at least as far back as the Book of Genesis in the Bible. There, thistles are mentioned when God curses Adam after he eats the forbidden fruit. Genesis 3:17-18 – “Cursed is the ground because of you… Both thorns and thistles it shall grow for you…” Clearly, if God includes thistles as part of His curse on all humanity, they are not a crowd favorite.
Regardless of why thistles are so widely disliked, our contempt for them causes serious problems for pollinators. This happens in two ways: 1) direct destruction of an important floral resource for pollinators, and 2) major side effects associated with #1.
Because thistles are so important to pollinators, our compulsion to destroy them is a major problem. Sure, some thistle species are invasive and can cause enough ecological damage that their control is warranted. Most thistle species, however, are targeted for destruction purely because they are thistles. Many of those are native wildflower species and are not at all aggressive or problematic. Regardless, there are few places where thistles are tolerated, let alone encouraged. The result is the loss of a big source of food for many pollinators.
While the loss of thistles themselves is a big problem for pollinators, the methods we use to eliminate them can have much bigger impacts. If we were content to dig thistles out of the ground one by one, things wouldn’t be so bad. Of course, that’s not always feasible – some perennial species such as Canada thistle are rhizomatous and can’t be killed by digging. Herbicide use is the other available option. Spot spraying individual plants or clumps can be relatively innocuous, but only if the person spraying is judicious and selective about what they spray.
However, working thistles one by one takes a lot of time, and just because we hate thistles doesn’t mean we want to spend a lot of time getting rid of them. Broadcast herbicide spraying, by airplane or boom sprayer, can kill lots of thistles in very short order. It’s a great way to get rid of all those unsightly pink flowers in one fell swoop…at least for that season. Unfortunately, broadcast spraying also kills a wide array of other wildflowers, and most of those never recover (the ones that do are the ones we tend to like least – like ragweeds).
The grand irony is that because broadcast spraying kills so many non-target plant species, the spaces left open by those dead wildflowers are usually colonized by thistles. Thus, while broadcast spraying is quick, it tends to perpetuate thistle populations by destroying their competitors. (Also, most large thistle populations are there because of chronic overgrazing or some other major disturbance that weakens perennial vegetation and creates space for thistles to grow. Broadcast spraying doesn’t address those underlying issues.) Oh, and by the way, killing off all the wildflowers in a pasture or roadside also wipes out the pollinators that depend upon them for food.
Our cultural dislike of thistles leads us to kill off as many as we can each year. Since thistles are a major food source for pollinators, that’s grave news for pollinator conservation. Our desire for more “efficient” ways to kill thistles has led to even worse news, however – the loss of plant diversity across millions of acres. Since plant diversity sustains pollinators by providing varied and consistent food through the season, losing that diversity at a large scale is devastating. We can rebuild some of what we’ve lost through restoration, and we can save what’s left, but only if we change the way we think about thistles. We’d better hurry; pollinator declines are not slowing down.
I think we need a thistle fan club. Who’s with me?? Let’s do this thing. I’ve come up with a basic logo and tag line (below) to get us started. Click here to get an easily printable version you can hang on your office door or tape to your car window. It’ll be a great conversation starter! In fact, let’s have fun with this. If you feel like it, take a picture of how you displayed the logo and put it on your favorite social media with the hashtag #thistlehelp. Not a social media person? Feel free to email me a photo – maybe I’ll collect some of them and use them in a future post. If you email me, please keep the file size below 1 mb… Use this email address: chelzer(at)tnc.org.
The bees and butterflies of the world are depending on you. This is going to sweep the nation, you’ll see!
One of the best outcomes from learning a lot about a group of species is that I start to see prairie through their eyes. That perspective has been really valuable for me and has led me to evaluate, restore, and manage prairies differently. Over the last couple years, I’ve been learning quite a bit about bees and other pollinators (and dragging you along with me through numerous posts on those species – sorry about that). As a result, when I look at prairies these days, I sometimes feel like I’m doing so through “bee goggles”.
What I’m seeing through my bee goggles these days is that food gets pretty scarce in the fall, and the end of this wildflower season is very near. Even a couple weeks ago, when Anne Stine and I were doing the last field sampling of bees for her research project (September 18 and 20), it was clear that most plant species were done blooming for the season. Most goldenrods were finished, as were sunflowers, tall boneset, and just about everything else. As a result, we didn’t see as many bees as we’d hoped to, and they were very concentrated on the few blooming flowers that were still around.
One group of flowers that was still blooming was the asters. In fact, heath aster (Aster ericoides) provided, by far, the greatest abundance of flowers we saw during those September bee surveys. Interestingly, however, even given the scarcity of other flowering plant species, we saw surprisingly few bees using heath aster. We did, however, see lots of hover flies (Syrphid sp) and quite a few wasps. Sure, there were a few bees here and there, including some little sweat bees and a few others, but not all that many. In addition to heath aster, there were two other larger-flowered asters blooming in a few prairies: New England aster (Aster novae-angliae) and panicled aster (Aster lanceolatus). Both of those seemed to host significantly more bee visitors than did heath aster, and New England aster – though pretty uncommon – was the most attractive of the two.
(For you botanists in the audience: yes, I know the genus of asters has changed, but I refuse to go along with it. Asters are asters, not Symphyo-whatever. Sue me.)
Pitcher sage (Salvia azurea) was another late-blooming species that was very attractive, at least to larger bees – as well as butterflies. However, while we saw scads of bumblebees on pitcher sage during our last bee survey period (August 19-20) we only found a couple this time around. Because of that, I assume the queens that will initiate next year’s new colonies have mated and are now finding a nice comfy place to spend the winter. Since producing fertilized queens is the ultimate goal of every bumblebee colony, the rest of the colony members can (and will) die happy, knowing they played their role successfully.
Interestingly, while looking for bees, we saw some widely scattered blooming plants of goldenrods, annual sunflowers, tall boneset, and a few others – even though the vast majority of plants within those species had long finished flowering. Some of those plants appeared to have been grazed by cattle or other animals, and so were behind schedule and trying to rush some flowers and seed production before the first freeze. Others just appeared to be late bloomers – in full flower, surrounded by others of the same species that were already decked out in seed heads. Maybe they were just a little different genetically? Regardless, those late individuals were getting abundant attention from bees and other pollinators and were clearly more attractive than heath aster… As long as they are able to get their seeds ripened before temperatures drop too low, those late blooming flowers should come out pretty well. As we harvest seed from some of those species this fall, it would be probably be smart for us to gather seeds from those plants that may be genetically inclined to bloom a little later than their counterparts. Maybe we can create restored prairies with a longer flowering period and give late-season pollinators a little autumn boost.
I don’t need bee goggles to see that fall has arrived. Our prairies have mostly turned golden brown, and while the range of colors has narrowed, it has been complemented by an incredible array of seed head architecture that lends grasslands a new texture. The subtle beauty of autumn prairies will last until next year’s green up starts, but it will be much quieter for a while without bees and the myriad other insects that make summer sound so alive. However, as with all prairie animals, bees have their own ways of surviving the coming winter, and will emerge from dormancy – along with the rest of the prairie – when the time is right in the spring.
I just finished a wonderful pollinator work shop with Mike Arduser here at the Platte River Prairies. Much of this workshop involved catching bees, using a dichotomous key to identify them to genus, and then pinning the bees on-site. I am pretty pleased with my collection, and I’ve decided to share a few of the fascinating factoids that are buzzing (I am so, so sorry) around my head.
Agapostemon virescens is my new favorite bee. They are eusocial, but not tyrannically so. There is no queen, all females can reproduce; they just choose to share a nest (from “The Bee Genera of Eastern Canada”; Packer, Genaro, and Sheffield 2007). I adore these utopian bees. They also happen to be gorgeous. I’ve included a picture of the male below. The female looks similar, but is all emerald without the striped abdomen.
Svastra obliqua is my second favorite bee. Their scopa (branched, pollen carrying hairs) are so exaggerated, they look like they are wearing giant fuzzy chaps. Big and easy to spot, they hang around annual sunflowers and could be confused (if you were squinting and using your peripheral vision) with a small bumblebee.
The Megachile family is another good group. Instead of having scopa on their legs, they carry pollen on their abdomens. This placement requires them to rub their bellies all over a flower when they forage. It’s a pretty amusing mental picture. Another reason to love the Megachile is that they can be field ID’d by ear. After conferring with my fellow pollinator work shop participants, we decided that, if the bumblebee is a Harley (low pitched, rumbling “BZZZzz”, then the Megachile is the sportbike (they make a high pitched “eeeeee” sound when they forage). Once you hear their whine, you won’t forget it. Megachiles are leafcutters, and they excise circular patches from leaves to build their nests. If you see a leaf that looks like a crazed administrator took a hole-punch to it, you should start listening for the Megachile whine.
Hymenoptera bonus: the cuckoo wasp. She’s wearing a rhinestone suit of armor.
There is so much more I wish to share! I foresee future posts about buzz pollination, specialists vs. generalists, combative cleptoparasites, and the potential for the hymenopteran community as an indicator of restoration success.
Hymenopterans are beautiful, sometimes adorable, with unusual life histories that make their study easy to enjoy. I am so pleased I get to spend time with these creatures during my fellowship here on the Platte River Prairies.
Thanks to a return visit by Mike Arduser of the Missouri Department of Conservation, it’s bee week in the Platte River Prairies. Mike came out to our sites a year ago to help us start thinking about our prairies from the perspective of bees and other pollinators. This year, he made a return visit and we’ve given him a full plate of activities.
On Monday, Mike and I spent the day inventorying bees at several of our prairies, assisted by Anne Stine (Hubbard Fellow) and Sam Summers (TNC volunteer). We are building upon the initial list of 57 bee species we found in 2012. Several new species have already been added to the list, and more are likely as we continue to look.
We hosted a pollinator ecology workshop on Tuesday, attended by about 40 people – mostly biologists who assist private landowners with habitat projects or who manage conservation lands. The objectives were to have Mike help us better understand basic pollination ecology and the needs of pollinator species – particularly bees, and to help us better incorporate bee habitat into our prairie restoration and management strategies. It was a great day, and everyone had their heads buzzing (sorry) with new information and ideas.
On Wednesday and Thursday, Mike is leading a smaller group of us through an intensive bee identification workshop. I’m looking forward to peering closely at the faces and private parts of bees through microscopes, and learning to differentiate between Melissodes, Colletes, Lasioglossums, and all the other bees in our prairies.
Less than a month ago, we saw Mike at the Grassland Restoration Network workshop in Columbia, Missouri. He gave a presentation in which he talked about a variety of pollinator-related topics, including some potential ways to use bees to assess the success of prairie restoration projects. One of Mike’s suggestions was to see what percentage of bee species in a prairie are specialist pollen feeders (oligolectic bees) and compare that percentage between restored (reseeded) and remnant (unplowed) prairies.
Pollen specialist bees feed only on pollen from one to a few flower species, whereas pollen generalists can feed from a wide variety of plant species. Specialists tend to be less common in small isolated prairies than in larger prairies, in part because they need a certain minimum population size of their host plants, which can be difficult to obtain in small prairies. Restored prairies might also lack that population size threshold, especially during the early establishment phase of a new seeding. In addition, restored prairies that are isolated from remnants might be missing specialist bees simply because the bees in those remnants can’t find them.
According to Mike, a couple of recent surveys in Iowa found that about 20% of the bee species in remnant prairies are pollen specialists. However, some early data from re-seeded Iowa prairies is showing much lower percentages of specialist bees – especially when those sites are isolated from large remnant prairies. If pollen specialists are not easy to attract to restored prairies, comparing the percentage of specialist bees in restored prairies to the percentage in nearby remnant prairies might be an important way to assess restoration success.
Mike suggested that another useful metric could be the number of cleptoparasitic bee species present in a prairie. Cleptoparasites, or cuckoo bees, are the cowbirds of bees – they lay their eggs in the nests of other bee species. Because each cleptoparasitic species tends to specialize on the nests of certain species or groups of bees, their presence could another interesting indicator of restoration success.
From our 2012 bee inventory data, I can make some preliminary, and very tentative, conclusions about the number of pollen specialists and cleptoparasites in our prairies. Of the 38 species we found in remnant prairies last year, 10 (26%) are pollen specialists and only 1 (3%) is a cleptoparasite. By comparison, of the 47 bee species we found in restored prairies, 12 (26%) are pollen specialists and 7 (13%) are cleptoparasites.
Those data are encouraging, but pretty sketchy because we were really just doing broad inventory work – not collecting data in a way that would allow for a good comparison. In addition, it clumps all our prairies together, so we can’t look at each one individually. Anne Stine (one of our two Hubbard Fellows) is going to help remedy that during the next couple months by conducting a short study. She do some standardized collection of bees from a variety of remnant and restored sites and then compare the percentages of specialists and cleptoparasites between those prairie types. That should give us a better feel for what’s going on.
In the meantime, it looks like a relatively high percentage of the bee species in our restored prairies are pollen specialists. That probably reflects positively on both the plant species diversity in those restored prairies and the fact that they are adjacent to remnant prairies – making bee colonization pretty easy. Since the main objective of our prairie restoration work is to enlarge and reconnect our remnant prairies, those early results are very promising. …But let’s see what Anne finds before we get too excited.
Now if you’ll excuse me, I have to go learn to tell the difference between Melissodes agilis and Melissodes desponsa. Wish me luck…
Mike Arduser has (mostly) finished identifying the bees we found during our insect week in early July this year. Though the data we collected during that week was just a first step, the early results are very positive. It appears that our restored prairies are providing adequate habitat for most bee species, including some that have fairly specialized needs for nesting or feeding habitat. Below is a summary of what we’ve found so far, what I think it means, and what our next steps are.
As a reminder, our restoration objective is to reconnect and enlarge existing prairies by converting nearby crop fields to high-diversity prairie plant communities. We hope the result is a larger, more connected, and more ecologically resilient prairie landscape. The diverse plant communities in those restorations have successfully established, and we’ve been able to measure that by tracking plant species diversity and floristic quality. It’s been more difficult to measure whether or not those restored prairies are actually stitching the surrounding landscape back together. Our insect week this summer was an important step in evaluating that.
Well, as promised, here are some early impressions from the time I spent looking around our Platte River Prairies with Mike Arduser (bees) and James Trager (ants) last week. I’ll know a lot more after Mike and James have time to sort through the all the insects we collected. Both have promised to send me annotated lists of the species we found, along with the locations each was found in. Once I get that information, the three of us will be able to have some more discussions about what the data tell us about the state of our prairies – from the perspective of bees and ants. It’s unlikely that our single snapshot of data collection will provide us with any major conclusions, but I have high hopes that our efforts will point out some paths I can follow during the next couple of years to flesh out the story.
The Platte River Prairies through the eyes of bees:
Obviously, plant diversity is important to bees, but the majority of bee activity last week seemed to be taking place on purple prairie clover, a species that is pretty abundant in both our remnant and restored prairies. I don’t know yet how many of the 40 or so bee species we collected were found (at least once) on prairie clover, but I bet it was at least 30%. In addition to purple prairie clover, hoary vervain was another fairly heavily used species (though nothing like the clover). In some ways, then, a few very accessible and productive flowering species seem to play a huge role in supporting bees – especially generalist species – in our prairies during this time of year. From talking with Mike, it sounds like that kind of heavy use of a few species is fairly common in other prairies he’s seen.
On the other side of the coin, roughly half of the bee species in our prairies (and most other prairies, I think) are specialist pollinators on a single species, or small group of species of flower. For these bees, the abundance and distribution of their particular host plants is obviously critical. We found bees that specialize on a number of different flowers, including those in the genera Callirhoe (poppy mallow), Physalis (Ground cherry), and Oenothera (evening primrose), among others. There were also a fair number of bees with slightly broader, but still restricted, diets. Many of the flowers used by specialist bees have other pollinators to help them produce seed, so the relationship is usually more critical to the bees than the flowers – though that’s not universally true. Some, like the ground cherries, have flower types that can’t easily be pollinated by insects other than those built to specialize on them.
Mike and I spent some time talking about our need to know more about what thresholds of flower abundance and distribution are really important for these specialist bees. For example, a prairie that has only a couple individual plants of ground cherry isn’t likely to be able to support a bee species that can only use that kind of plant. But how many plants does an individual bee need to raise a brood? And how close together do those plants need to be in order for bees to find and pollinate them efficiently?
From the plant species’ standpoint, how many individual plants (and at what density?) does it take to attract enough pollinators to provide sufficient pollination for the plant population? It’s a particularly important question when talking about rare plants, which often occur in small scattered populations. It’s also important for our degraded remnant prairies that have very few individuals of even some more common plant species. If we don’t have enough plants to garner effective pollination, the population may not reproduce – or sustain itself in the prairie. It makes me think about the way we approach our overseeding efforts in those degraded prairies. Maybe we need to be using lots of seed in small areas to establish patches of flowers with enough density to attract pollinators, rather than spreading that seed more lightly across large areas. Very thought provoking. I need do some investigation, and see whether we’re getting seed production from plants that are scattered at low densities across degraded remnant prairies.
Mike needs to spend some more time looking at the data we collected this week to see if there are differences in the bee communities between our restored and remnant prairies. We spent quite a bit of effort collecting bees from purple prairie clover and hoary vervain across a range of restored and remnant sites in the hope that we could see whether or not the same bee species were visiting the flowers in both site types. Granted, we only had about three good days of field data collection to draw conclusions from, but I hope it was enough to give us at least an initial glance at what’s going on. To do it right, of course, we’d need to look at the abundance and density of plants at each site, and focus on more than just the number of bee species using them at each site – the number of total daily visits, for example, would also be important, as would seed production and other measures. I’m hoping to collect some more bees throughout the rest of this season to give us a bigger slice of the total picture to look at. It’d be great to see a pattern interesting enough that we can build a graduate student project out of this, and take a much closer look at what’s happening. Anyone looking for a good project?
Again, Mike still needs to finish sorting through and identifying the bees we collected this week. However, he did notice a few interesting discrepancies between what he expected to see at our sites and what we actually found. For example, we really didn’t see many (any?) twig-nesting bees, and only two species of parasitic bees. At this point, it’s hard to know if that’s because the bee fauna here is just different than what he’s used to seeing further east, if our sample was too small to fairly represent what’s actually here, or if there’s something functionally missing from our prairies.
On the other hand, there were a fair number of bee species that are rare in Missouri and other eastern prairie states, but common in our prairies here. One of those is often called the “ghost bee” because of its fuzzy white appearance and the difficulty of finding it in eastern tallgrass prairie. When Mike saw one in my net on our first day of sampling, I could tell from his expression that it wasn’t just another fuzzy bee… Unfortunately, after I came home that night and bragged to my family (who didn’t seem that excited) that I’d caught the elusive ghost bee, we ended up seeing them pretty often during the rest of the week – somewhat dampening my sense of accomplishment. And, just to rub it in further, during our public field day on Friday, two Pheasants Forever biologists showed Mike some very nice photos they’d taken of the same bee species from another prairie about an hour north of us. Sure, it’s great to know that the species appears to be doing well in this part of the world, but it did knock the air out of my balloon a little… On the other hand, how great is it that there are Pheasants Forever biologists out taking photos of bees in prairies?! Awesome.
What about ants?
It turns out that ants provide an interesting contrast to bees in terms of how they perceive prairie “quality”. While the diversity and abundance of bees in a prairie is heavily dependent on the diversity of flower plants, ants tend to look more at habitat structure than at plant species. For example, James says that one very important attribute of prairies is the attractiveness of its habitat for recently-mated females looking for a place to start a new colony. One significant factor for those females is the presence of enough bare ground to allow them to see whether or not an area is already occupied by colonies of potential competitors. More broadly, prairies that are most attractive to ants tend to be those that have a lot of variation in plant density and structure. Prairies that are dominated mainly by grasses are usually too homogenous to be very ant-friendly. So, while ants might not respond directly to plant diversity, prairies with good plant diversity may be more likely to have the kind of structural diversity that ants are looking for.
After seeing the kind of fire and grazing management we’re using on our sites, James’ opinion was that we’re probably doing a pretty good job of facilitating ant habitat. Our grazing helps create the kind of structural variation that ants tend to like, and our stocking rates are light enough that we aren’t likely to be compacting the soil to the extent that it might negatively impact them. However, as with Mike, James only had a few days to look at our prairies and the ants living there, so it’s hard to draw too many conclusions – and he still needs to finish sorting and analyzing the data we collected this week.
James, along with Laura Winkler, a graduate student from South Dakota State University who joined us for the week, caught about twenty ant species in our prairies. They collected some of those ants by just walking around and looking for them. Other ants were found by setting pitfall traps or laying out baits that ranged from chicken skins and canned meat to pecan cookies. From his initial impressions, James said we had a surprisingly high abundance of a few ant species, but there were at least a couple of ant species he expected to be common here that we never saw. It’s hard to know whether that’s because they’re really not here or because we just missed them during our limited sampling time. In general, however, James felt that we might be missing some of the more common eastern prairie ants, and he wasn’t seeing western species that he would have expected to fill the same kinds of roles. If that’s an accurate picture of the ant communities in our prairies, it makes me wonder whether that’s just the way prairies in our part of Nebraska are, or if there is something going on that we should be addressing. I guess I’ll wait to hear more from James before I start worrying too much about it…
Because of the limited time we had, and the great variation in management and soil types across our prairies (not to mention this summer’s drought) it wasn’t really possible to do a good direct comparison of the ant communities between our remnant and restored prairies. However, I hope that James’ data might still give us some hints about whether or not there is something to follow up on in that regard. Because I know our restored prairies have some soil characteristics that are pretty different from remnant prairies that haven’t been farmed, I expect there to be some differences. Whether or not they’re important differences – or correctable – is something I don’t know…yet.
I’m extremely grateful to both Mike and James – as well as Laura – for giving up an entire week of their time to come out to explore our prairies and help me learn to think differently about them. As always happens when I spend time with intelligent people who are experts in their particular subject matter, I was awed both by their level of knowledge and the complexity of the worlds they study. Everywhere we looked, Mike and James shared fascinating stories about nearly every insect that flew or crawled by. In addition, both were very knowledgeable about ecology in general, which led to fantastic discussions about much broader topics than just invertebrates. It was a week that will keep my brain buzzing for a very long time, and I can’t thank them enough for coming.
I’ll keep you updated as I get more information and have some time to synthesize it…
This is my week to learn everything I can from James Trager and Mike Arduser – entomologists and ecologists from Missouri. They (and their wives!) have very graciously agreed to spend the week in our Platte River Prairies to help inventory our insects, try to teach me a few things, and brainstorm ways I can evaluate our prairie restoration and management work from the perspective of insects. It’s going to be a great and busy week.
We started the week yesterday in Pawnee County, Nebraska (southeast corner of the state). Pawnee County was on the way to our Platte River Prairies, so I met James and Mike down there and we spent the morning looking around. Both James and Mike have helped identify insects from those prairies for various research projects I’ve been involved with, so it was good for them to be able to see some of the prairies those insect samples had come from. It was a little wet for collecting many insects yesterday, but we got to visit some interesting prairies and had some good discussions. We were joined by Kent Pfeiffer and Krista Lang of Northern Prairies Land Trust, and Bethany Teeters, a PhD student at the University of Nebraska.
Even in the first hour or two in the prairies, it was clear that I’m going to learn a tremendous amount this week. James and Mike were definitely seeing the prairies through different lenses than I was, and noticing insects and habitat qualities I wouldn’t have thought about. Back in graduate school, I studied the impacts of habitat fragmentation on grassland birds, and I remember beginning to look at prairies differently as I learned more about how birds evaluate them. I can see that I’ll be doing some similar perspective shifting again this week.
For those of you coming to our field day this Friday, you’ll have a chance to meet and interact with Mike and James – and other experts. For the rest of you, I’ll try to capture some of the big lessons from the week in future blog posts.
Thank you to Kent, Krista, and Bethany for taking the time to help show Mike and James (and me!) around the prairies yesterday. Also, thank you to Prairie Biotic Research Inc. for the grant that is helping to fund the travel costs for Mike and James to come work with me this week.