Conserving plants is one of the most significant challenges of our time—and a major focus at the Chicago Botanic Garden. From studying soil to banking seeds, from restoring habitats and protecting endangered plant species to developing new ones, Garden scientists are fighting plant extinction, pollution, and climate change through diverse and exciting research.
Pop quiz: What kind of natural habitat is increasing in urban areas? This is not a trick question. Rather, the answer offers a slice of good news on a planet that has been increasingly turning from green to gray.
Kelly Ksiazek-Mikenas, Ph.D., in the Plant Science Lab
Dr. Ksiazek-Mikenas, a former biology teacher, spent six years studying these engineered habitats and their potential to support biodiversity.
The plant scientist is now eager to share her findings: When started carefully and with a long-term plan in mind, these sites do grow up to support species, natural communities, and genetic diversity.
“When you have these three pieces working, you have a good foundation that should sustain plant life over long periods of time and live through environmental changes, and that look and function like a diverse prairie,” she said.
Dr. Ksiazek-Mikenas examined shallow (up to six inches of soil depth), low-moisture roofs from Glencoe, Illinois, to Neubrandenburg, Germany, before reaching that conclusion. While the roofs within the United States are generally younger, some in her German sites were up to 93 years old, providing a mix of data about green roofs at all ages. She also studied data sets and conducted shorter-term experiments to clarify the qualities green roofs need to succeed.
Dr. Ksiazek-Mikenas sets up insect traps in 2013 on a green roof in downtown Berlin.
Her work had its ups and downs. She arrived in Germany looking for similarities, expecting the insect and plant species on one roof to mirror that on the others. Rather, she found differences between roof gardens. After a deep dive into data, she found the secret. Although the plant species differed between gardens, those that grew well shared the traits of being stress-tolerant and adept at establishing themselves in new areas.
She was concerned by the lack of diversity on individual roof gardens both in Germany and in her study sites in Chicago.
Back at the Chicago Botanic Garden, she set up an experiment to test how different soil types would affect which plants were successful, and whether she could create a more diverse community on one rooftop by planting both rock and sand prairies.
She planted her experimental plots on the Josephine P. & John J. Louis Foundation Green Roof Garden North on the Daniel F. and Ada L. Rice Plant Conservation Science Center and monitored activity over three years. She found success in growing a more diverse habitat. In related work at the same site, she confirmed that native plantings, rather than the common sedum plant mix used on roof tops, offered benefits similar to a native prairie when it comes to storing rainwater, for example.
The Plant Science Center’s Green Roof Garden is an important resource. Planted in 2009, it serves as a living laboratory, classroom, research site, and a source of inspiration to visitors.
A blooming population of Penstemon hirsutus was part of Dr. Ksiazek-Mikenas’ experiments.
She then expanded to include plots on the Ellis Goodman Family Foundation Green Roof Garden South to study genetic diversity. She compared the genetic diversity of populations established from nursery stock to natural populations, finding more diversity in the natural populations grown from wild collected seed.
On the heels of that finding, she studied populations on green roofs in Chicago near Lake Michigan to find out if the plants were able to share their genetic material with plants on neighboring roofs through pollination. She was thrilled to confirm that they did, as the exchange of diverse genetic material is essential for the long-term health of a species.
Although there are limitations to green roof gardens, mainly due to the lack of soil depth and disconnected setting, Dr. Ksiazek-Mikenas is optimistic about their ability to sustain native species. She has presented her work at numerous conferences across the globe to academics and those in the landscaping industry.
Two prairie species in Dr. Ksiazek-Mikenas’ experimental plots—Ratibida pinnata (foreground, right) and Lespedeza capitata (background, left)—bloom on a green roof on the Peggy Notebaert Nature Museum in Chicago.
“In the future, I hope that green roofs can continue to provide ecosystem services to people but also increasingly support a wide variety of urban biodiversity,” she said.
The motivated researcher is ready to move ahead with her career and intends to continue to bring her unique perspective to future students and to the development of more green infrastructure in this growing world.
Why did five Midwestern horticulturists hike through the oak-hickory forests of the Missouri Ozarks? And why did we need a desiderata? The first question is easy—we were on the trail of specific wildflowers and woody plants to preserve and add to our collections.
Collections trip horticulturists Michael Jesiolowski, Tom Weaver, Josh Schultes, Kelly Norris, and Steve McNamara (left to right)
In a trip funded by the Plant Collecting Collaborative (PCC), a consortium of public gardens, Tom Weaver (horticulturist, Dwarf Conifer Garden) and I (senior horticulturist, Entrance Gardens) joined Kelly Norris (the trip leader) and Josh Schultes of the Greater Des Moines Botanical Garden, along with Steve McNamara of the Minnesota Landscape Arboretum. Before we left, our desiderata—or essential list of desirable plants we would target—was developed, based on what plants our gardens deemed important for conservation, to fill a gap in our collections, or add beauty to our display gardens. And of course, we had the proper state and federal permits in hand for seed collecting. The six areas that we explored were typically oak-hickory forests, which opened up to rocky-soiled glades and provided for plentiful opportunity for collecting wildflowers.With an eye for distinct plant material and genetic diversity, we roamed through the uneven Ozarks terrain, but we weren’t tied to our wish list—we also found a couple of surprises.
Glade opening at Roaring River State Park
Since seed-grown plants are reproduced sexually through pollination, via wind or insects/animals, they are genetically variable. A variety of genes can give each plant the best chance to exhibit a specific phenotype, or physical appearance, and better adaptability to survive pests and diseases. Where seeds are collected could have significant implications on whether a plant can survive in a given environment or not. For instance, we collected seeds of Echinacea paradoxa (yellow coneflower) from its northern most growing region, in Ha Ha Tonka State Park in Missouri. Selecting seeds of Missouri provenance gives this wildflower a better chance of survival in our region, rather than if the seeds had been collected in Texas. Plants that have a different phenotype from what we commonly observe in northern Illinois were of special interest to us. Fruit from Diospyros virginiana (common persimmon) was collected on a 4-foot-tall tree in Mark Twain National Forest because it is unusual to see fruit on a tree of such short stature. In a similar fashion, Symphoricarpos orbiculatus (coralberry), was collected from the Big Buffalo Creek Conservation Area, after we all remarked at the stunning ornamental quality of the fruit display.
Yellow coneflower (Echinacea paradoxa)
Persimmon (Diospyros virginiana)
Josh Schultes examines possumhaw holly for collection.
In some cases, we came across desirable plants, but they had already dropped their seed for the year, or simply didn’t produce any due to drought-induced stress. With the aid of GPS, we marked these areas so future explorers to the Ozarks are aware of these plants for their potential collections. For example, Boyce Tankersley, the Chicago Botanic Garden’s director of living plant documentation, was a part of a team that collected in many of these same areas in 2005; their field data was helpful in our search.
Dotted blazingstar (Liatris punctata)
Although the Ozarks region experienced a late-summer drought that negatively impacted seed production in some instances, we were still able to make 71 collections from October 12 to 16. Our seeds will be grown in our plant production greenhouses. Once they achieve a certain size, they will be distributed to PCC members and planted in the Garden. I am ecstatic to cross Liatris punctata (dotted blazingstar) off the desiderata for use in my gravel garden project in parking lot 1. The seeds we collected should be ready to plant in these beds in two years.
Home gardeners can sympathize: not every seed that is planted grows.
This truth extends to restored prairies that are grown from seed mixes, according to Rebecca Barak, Ph.D., who completed research this year examining the success of individual species within seed mixes, and their combined potential to power up to the diversity level found in remnant prairies.
A healthy, diverse prairie
Urban and agricultural development has left us with less than one-tenth of one percent of prairieland, which is vital part of our ecosystem. Today, the prairie can be found only in small patches, and scientists at the Chicago Botanic Garden study prairie plants and their chance for survival amid changing climates and landscapes. For Dr. Barak, a key question is what restored plant communities will look like.
Restored prairies can and do grow in all kinds of places, according to Barak, who conducted fieldwork at dozens of sites within an hour or two of Chicago. From a small playfield behind a nature center to the grounds of a temple to a large swath of acreage in the suburbs, she and her team visited each restored prairie site to compare the plant communities to the mix of seeds that were planted there initially.
“I studied that on the ground—how do prairies differ, how do seed mixes become prairies, and how can we tweak those seed mixes to improve diversity outcomes for restored prairies,” explained Barak, who recently earned her doctoral degree from the Chicago Botanic Garden and Northwestern University and is now a post-doctoral researcher in a joint appointment between the Garden and Michigan State University.
To conduct her fieldwork, she outlined a 50-meter-long transect in each study prairie, and marked off a large circle every 5 meters along the way. Within the circle, she and her collaborators counted all the plant species they could find. They compared those notes to a walk-through of each site months later as bloom cycles changed.
A native of the Chicago suburbs, Barak made unofficial discoveries that warmed her prairie-loving heart.
“I’ve lived here almost all my life and there were all these preserves that I didn’t know about,” she said. Small corners of the city were transformed into lush green spaces, such as the Burnham Wildlife Corridor. Suburban sites such as Orland Grassland were larger and more delightful each season than she anticipated.
After summer months spent documenting and counting, she compared the list of existing plants to the list of seeds that were planted from the original seed mix. She found that less than 50 percent of the species diversity survived from seed to plant. “A lot of species are lost along the way,” she noted.
The plant mix within the restored prairies was then compared to historical data from 41 remnant prairies across Illinois—sites that had never been altered for other purposes. In addition to her findings about the success rate of seeds planted in restored prairies, “I found that species in restored prairies are more closely related to one another than species in remnant prairies,” said Barak.
The David H. Smith Conservation Fellow is not only tuned in to the number of species found in each prairie, but also to how well they represent a variety of evolutionary threads. “We think about how spread out plants in the prairie are across the evolutionary tree of life. Maybe, if you are getting more branches on the tree, your community will function better, or differently,” she noted.
“When we look at remnant and restored prairies, we find that there are differences in biodiversity and there are opportunities to increase diversity of restored prairies. In order to do that we have to think about the seed mixes that are being used,” she added.
In doing so, Barak anticipates that a higher level of diversity will support more functions like serving as habitat for pollinators.
Her detailed findings will be published this August in the Journal of Applied Ecology.
Spiderwort (Tradescantia)
In addition to the benefits of prairies—such as storing rainwater and carbon dioxide—they also provide opportunities we can all enjoy each time we visit, said the scientist and former teacher. “I think it’s about more than that [the ecological benefits]—it’s about teaching people our natural heritage, thinking about habitats that are unique and special to our area, getting people to notice biodiversity, and recognizing that it can even happen in the city or suburbs.”
Imagine an episode of the Jerry Springer Show in which the paternity of a child will be determined. Now imagine that instead of human beings, the show is focused on plants, and the issue at hand is the paternity of seeds produced by a given flower.
Next, consider that instead of just two candidate dads, there are dozens or even hundreds of individuals that could have fathered those seeds. What would you expect to find out at the end of the episode?
New research by biologists at Chicago Botanic Garden and the University of Arizona brings such a scenario into reality, and the “big reveal,” while not quite as dramatic as what you’d typically see on the Springer show, offers new insights into plant mating. The paper, titled “Pollinator identity and spatial isolation influence multiple paternity in an annual plant,” was published online today in Molecular Ecology.
“Biologists have known for decades that multiple paternity is common in plants—that is, the seeds contained in a fruit will often have been fathered by many different individuals,” said Matt Rhodes, a Ph.D. student in ecology and evolutionary biology at the University of Arizona. “While we have long had a basic understanding of how multiple paternity occurs in plants, we wanted to explore how it might be influenced by some of the messier aspects of pollination ecology.”
Much of this messiness stems from the fact that plants are sessile: once they start growing, they’re stuck where they are. “One important consequence of this immobility is that plants can’t seek out mates on their own,” Rhodes explains. “Instead, most flowering plants entrust the mating process to animal pollinators that move pollen from flower to flower. On top of that, some individuals are surrounded by potential mates while others are spatially isolated. There are good reasons to expect both of those factors to influence multiple paternity, and that’s what motivated our study.”
In the video above, pollen is deposited on the proboscis and body as hawkmoths (Hyles lineata and Manduca quiquimaculata) visit flowers of Oenothera harringtonii. (Video: K. Skogen) View video on YouTube here.
To address these issues, Rhodes went to the grasslands of southeastern Colorado with Jeremie Fant and Krissa Skogen, conservation scientists at the Chicago Botanic Garden who co-authored the article. They studied a rare evening primrose species with a strange twist in its pollination ecology: its flowers are visited by large-bodied hawkmoths at night and comparably smaller-bodied bees during the morning. “Based on these differences in body size as well as some important differences in behavior, we predicted that flowers visited by hawkmoths would mate with a greater number of fathers than those visited by bees,” said Skogen. “Because these floral visitors are active at different times of day, we were able to test this prediction with a fairly simple experiment in which we limited different flowers on a plant to visits from either hawkmoths or bees. We also predicted that multiple paternity would be less likely for individuals that were farther away from potential mates.”
Hyles lineata visits an Oenothera harringtonii flower; note the pollen on the moth’s head and body.
(Photo: S. Todd)
A Lasioglossum bee collects pollen from the anthers of an Oenothera harringtonii flower without coming into contact with the stigma. (Photo: S. Todd)
After collecting the seeds from these plants, the researchers spent months examining seed DNA in the genetics lab. “By comparing the seeds’ DNA to the DNA of the maternal plants from which we collected them, we were able to figure out which parts of the DNA came from the father,” explains Fant. “We then screened that paternal DNA against all of the individuals in the population—which in our case included more than 300 plants spread across 2 square miles of the landscape—to find the most likely father for each of the seeds we collected.”
For the most part, the results were consistent with the researchers’ predictions. “We found that on average, flowers visited by hawkmoths mated with nearly twice as many different fathers as flowers visited by bees,” said Rhodes. “We also found that spatially isolated individuals were far less likely to mate with multiple different fathers. Overall, it looks as though plant ‘promiscuity’ depends both on what kind of animal visits the flowers, and how far away that individual is from potential mates.”
Scales from Hyles lineata were deposited on the stigma of an Oenothera harringtonii flower. (Photo: K. Skogen)
In addition to providing a more thorough account of factors that can influence multiple paternity in plants, the results also allow researchers to consider how plants might be affected by the loss of certain pollinators. “This study allows us to make predictions about how some plants may be affected if particular pollinators disappear. Hawkmoths play an important role in moving pollen from plant to plant; if they decline in large numbers or are lost completely, there may be cascading effects on the success of future generations of hawkmoth-pollinated plants” said Skogen.
Comanche National Grassland, Colorado— the shortgrass prairie where the study was conducted. (Photo: K. Skogen)The field team in Colorado (left to right: Kelly Ksiazek, Matt Rhodes, Sadie Todd, Evan Hilpman, Krissa Skogen, and Jeremie Fant)
The number of women in science is pretty dismal. Despite earning about half the doctorates in science, only 21 percent of full science professors in the United States are women,* but I feel very fortunate to work at an institution committed to inclusiveness and diversity. At the Chicago Botanic Garden, 25 of our 47 scientific staff are women; our graduate student body is 61 percent female.
Still, implicit gender biases persist in science, resulting in fewer women in top positions, along with women earning less pay, winning fewer grants, and publishing fewer papers. This comes at a time when we are faced with numerous grand challenges in science and need a diversity of approaches to tackle those challenges.
In the Chicago Botanic Garden’s science program, we are conducting research on how human activities are affecting plants through climate change, habitat fragmentation, introduction of invasive species, pollinator loss, pollution, and more. These threats to plants are unlikely to diminish in the foreseeable future, and we are finding ways to conserve plants in changing and challenging environments. We are working hard to protect the plants and plant communities upon which we all depend. We are also working hard to create a pipeline into science for all—especially traditionally under-represented groups—through our Science Career Continuum, because diversity of plants and diversity of scientists are both good things.
Left to right: Krissa Skogen, Ph.D., is studying hawkmoth pollination with Victoria Luizzi (Amherst College Student, NSF REU Student, Summer 2016), Emily Lewis (research assistant), Andrea Gruver (research assistant), Tania Jogesh (postdoc), and Kat Andrews (PBC M.S. student). Dr. Skogen is a conservation scientist and manager of the Conservation and Land Management Internship Program.
Meet some of our women scientists:
Lauren Umek studies how invasive species change plant communities and soil properties in the Chicago region and how this can improve restoration methods.
Nyree Zerega studies evolution/genomics in underutilized tropical fruit trees and their wild relatives to promote and conserve food diversity.
Botanist, seed conservationist, and geographer Emily Yates has conserved thousands of seeds to protect the native tallgrass prairie ecosystem of the Midwest.
Ph.D. candidate Colby Witherup studies plant DNA, looking for signs of evolution in genes that control sexual reproduction.
Evelyn Williams, Ph.D., (left, with Adrienne Basey) traveled to Guadalupe Nation Park in Texas to study the shrub Burgess’ scalebroom.
Amy Waananen studies populations of purple coneflower (Echinacea angustifolia) in western Minnesota as a research assistant for The Echinacea Project, a long-term ecological study that began in 1995.
Mary Patterson studies restoration, invasive species, and fire ecology with a focus in the Western United States.
Joan O’Shaughnessy manages the Dixon Prairie at the Garden.
Kelly Ksiazek-Mikenas studies how green roofs can provide habitat for native plant species.
Andrea Kramer, Ph.D., conducts research on native plants to support ecological restoration that sustains people, wildlife, and the planet.
Rachel Goad (far right) is a botanist with a background in restoration ecology and a keen interest in native plant conservation.
Louise Egerton-Warburton, Ph.D., does work examining soil fungal diversity and functioning and its role in ecosystem processes.
Research assistant Susan Deans uses neutral genetic markers to examine how well gardens and conservation collections capture the remaining wild genetic diversity of threatened Hawaiian plant species.
