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.
Peter DeJongh is a first-year master’s student studying land management and conservation in the graduate program at Northwestern University and the Chicago Botanic Garden. His academic focus is on developing strategies to optimize plant and wildlife conservation and restoration. He aims to work in applied conservation or environmental consulting upon completion of his degree.
Imagine a large, beautiful canopy tree standing in the middle of a lush, tropical rainforest. This centuries-old tree produces thousands of seeds every year that densely litter the forest floor around it. Where then would you imagine its seedlings are likely to spring up? Probably in the seed-covered area around the tree right? Well, according to the Janzen-Connell model, you’d be wrong.
Daniel Janzen and Joseph Connell are two ecologists who first described this phenomenon in the early 1970s. They put their exceptional minds to the task and independently discovered that the probability of growing a healthy seedling was actually lower in the areas with the most seed fall. They hypothesized that seed predators and pathogens had discovered the seed feast around the parent tree and moved in, preventing any seeds in the area from growing into seedlings. These predator pests include beetles, bacteria, viruses, and fungi, and have been labelled as host-specific predators and pathogens since they appear specifically around the parent tree, or host.
This Malaysian silverleaf monkey eats fruit as part of its diet, dispersing seeds far beyond the canopy line.
Janzen and Connell’s hypothesis shows just how important the animals that eat the seeds are to the parent tree. These primates, birds, and other vertebrates move the seeds to different areas where they can successfully grow without being bothered by those pesky host-specific predators. Without these animal helpers, the forest couldn’t continue to grow, and the world’s most diverse areas would be in serious trouble.
Students in the Chicago Botanic Garden and Northwestern University Program in Plant Biology and Conservation were given a challenge: Write a short, clear explanation of a scientific concept that can be easily understood by non-scientists. This is our fifth installment of their exploration.
Life on the prairie hasn’t been a breeze for the beautiful eastern prairie fringed orchid (Platanthera leucophaea).
Once common across the Midwest and Canada, the enchanting wildflower caught the attention of collectors and was overharvested throughout the 1900s. At the same time, large portions of its wet prairie, sedge meadow, and wetland habitat were converted to agriculture. By 1989, just 20 percent of the original population of Platanthera leucophaea remained, and the orchid was added to the federally threatened species list.
Claire Ellwanger takes a leaf sample in the field.
The struggles of the captivating orchid did not go unnoticed. Its lacey white flowers and unique biological attributes sparked a passion in scientists and volunteers across the Midwest who began gathering leaf samples for genetic analysis and recording measurements on the health of certain populations. Some volunteers dedicated decades to this work, and many continue to monitor their assigned location today.
As long ago as the mid 1800s, an earlier generation of the wildflower’s enthusiasts had preserved samples of actual plants, pressing them onto archival paper with their field notes and placing them in long-term storage facilities called herbaria, for future reference. As it turns out, some of the plant materials they saved are from populations that no longer exist.
Now, all of that data is coming together for the first time in a research study by graduate student Claire Ellwanger.
The master’s degree candidate—in a Plant Biology and Conservation graduate program run by the Chicago Botanic Garden and Northwestern University—is using modern analysis tools to uncover the genetic history of the species. What she finds will give scientists a better picture of the present-day status of genetic diversity of the species, and insight into the best ways to manage it for the future.
Claire Ellwanger measures orchid seed pods in the field.
“This orchid is a pretty interesting species because there has been this massive volunteer effort for over 20 years to restore it in Illinois,” noted Ellwanger, who said that Illinois currently houses more populations, or locations, of the species than any other state.
She is focused on collecting and analyzing genetic information on the remaining plants, working with field collectors in the Midwest from Iowa to Ohio, and also from Maine. She is examining the genes, or DNA, of each of the sampled populations, along with genetic information she collected at eight sites right here in Illinois.
Ellwanger is also extracting DNA from the older herbarium samples to better understand how much genetic diversity was a part of the species in the past. “The herbarium samples will allow us to get a sense of historic genetic variation to compare to levels today,” she explained.
Along with her thesis advisor, Garden molecular ecologist Jeremie Fant, Ph.D., she is especially interested in finding ways to maintain genetic diversity. “We know that if you are able to preserve the most genetic diversity in a species, it is more likely to persist for longer,” she explained.
Extracted DNA is ready for analysis in the laboratory.
In the lab today with her research assistant, Laura Steger, she uses a genetic fingerprinting technique on all groups in her study subjects. By watching the same sequence of genes over time and locations, she can see clear patterns and any changes. The bonus to it all is that “understanding more about these plants and their genetic variation will be pretty applicable to other species that have undergone the same processes,” she noted.
As scientists and volunteers worked in the field over the last several decades, they did more than collect genetic information. They also took steps to boost new seed production by hand pollinating plants or conducting a form of seed dispersal. Through her study, Ellwanger is also tracking the success of each technique. “I’ll be able to complete a genetic comparison over time to see if these recovery goals are achieving what they set out to do,” she said, by comparing the genetic composition of a given population from the recent past to today.
A compound light microscope reveals some plump, fertile embryos inside seeds.
At sites Ellwanger visited personally, she collected seeds as well, and brought them back to the lab for examination. There, looking under a compound light microscope, she checked to see what percentage of seed embryos from the sites were plump and therefore viable. Her findings offer an additional perspective on what her genetic analysis will show. After examination, the seeds were returned to their field location.
In early analysis results, “it looks like reproductive fitness does differ between sites so it will be really interesting to see if those sites that have lower reproductive fitness also have higher levels of inbreeding,” noted Ellwanger. Inbreeding, the mating of closely related individuals, can result in reduced biological fitness in the population of plants. In such cases, it could be helpful to bring in pollen or seed from other populations to minimize mating with close relatives and strengthen populations for future generations.
The eastern prairie fringed orchid will soon be better understood than ever before. The findings of the study may also provide insight into other problems that may be happening in the prairies where they live. “Orchids will be some of the first organisms to disappear once a habitat starts to be degraded. If we can better understand what’s going on with this plant it, could help out similar species,” said Ellwanger.
The researcher is looking forward to the impact this work could have on the future of the plant and the habitat that sustains it. “What motivates me about research is definitely the conservation implications,” said Ellwanger, who developed her love of conservation while growing up on the East Coast and learning about the complex systems that play a role in the health of the environment.
Dr. Evelyn Williams is an adjunct conservation scientist at the Garden. She’s interested in genetic diversity at multiple scales, from the population to the family level. While at the Garden, Dr. Williams has worked on rare shrubs from New Mexico (Lepidospartum burgessii), systematics of the breadfruit family (Artocarpus), and using phylogenetic diversity to improve tallgrass prairie restorations.
When a scientist says that chimpanzees are related to humans, or that chickens are related to dinosaurs, what do they mean?
They mean that chimpanzees and humans share a common ancestor from many thousands of generations ago. Although that shared great-great-great-great-(etc.)-great-parent lived many years ago, that shared ancestor lived more recently than the ancestor that humans share with dogs. So humans are more closely related to chimpanzees than dogs because they have the most recently shared ancestor. Scientists call this the “most recent common ancestor.”
This most recent common ancestor wasn’t a chimp, and it wasn’t a human—it was a different species with its own appearance, habits, and populations. One of these populations evolved into humans, and one of the populations evolved into chimpanzees. We know this because of a field of study called “phylogenetics.” Scientists use phylogenetics to study how species are related to each other.
Using DNA sequences, scientists construct tree-like diagrams that trace how species are related. A human’s DNA is more similar to a chimpanzees’ than to a chicken, so a tree diagram would connect humans and apes. Dinosaurs and chickens would be shown as related as well, and then these two groups would be connected.
Students in the Chicago Botanic Garden and Northwestern University Program in Plant Biology and Conservation were given a challenge: Write a short, clear explanation of a scientific concept that can be easily understood by non-scientists. This is our fourth installment of their exploration.
Becky Barak is a Ph.D. candidate in Plant Biology and Conservation at the Chicago Botanic Garden and Northwestern University. She studies plant biodiversity in restored prairies, and tweets about ecology, prairies, and her favorite plants at @BeckSamBar.
A dark, stinky plume of smoke rising from a nature preserve might be alarming. But fire is what makes a prairie a prairie.
A prairie is a type of natural habitat, like a forest, but forests are dominated by trees, and prairies by grasses. If you’re used to the neatly trimmed grass of a soccer field, you may not even recognize the grasses of the prairie. They can get so tall a person can get lost.
Prairies are maintained by fire; without it, they would turn into forests. Any chunky acorn or winged maple seed dropping into a prairie could grow into a giant tree, but they generally don’t because prairies are burned every few years. In fact, fossilized pollen and charcoal remains from ancient sediments show that fire, started by lightning and/or people, has maintained the prairies of Illinois for at least 10,000 years. Today, restoration managers (with back up from the local fire department), are the ones protecting the prairie by setting it aflame.
Garden ecologist Joan O’Shaughnessy monitors a spring burn of the Dixon Prairie.
New growth emerges a scant month after the prairie burn.
Prairie plants survive these periodic fires because they have incredibly deep roots. These roots send up new shoots after fire chars the old ones. Burning also promotes seed germination of some tough-seeded species, and helps keep weeds at bay by giving all plants a fresh start.
Students in the Chicago Botanic Garden and Northwestern University Program in Plant Biology and Conservation were given a challenge: Write a short, clear explanation of a scientific concept that can be easily understood by non-scientists. This is our third installment of their exploration.
Alicia Foxx is a second-year Ph.D., student in the joint program in Plant Biology and Conservation between Northwestern University and the Chicago Botanic Garden. Her research focuses on restoration of native plants in the Colorado Plateau, where invasive plants are present. Specifically, she studies how we can understand the root traits of these native plants, how those traits impact competition, and whether plant neighbors can remain together in the plant community at hand.
Life for plants on land is hard because the environment can become dry. Water is important because it is used when plants take in sunlight and carbon dioxide to make energy; this is called photosynthesis. In fact, the largest object in a plant cell is a sack that holds water. Without water, plants would die.
Plants first evolved in water, which is a comfortable place: there is little friction, you almost feel weightless, and…there was plenty of water back then. These plants had no difficulty photosynthesizing, as water diffused quite easily into their leaf cells! They had little use for roots.
Evolving Plant Structures
In the time plants evolved to live on land (100 million years later), water shortages and the need to be anchored in place became issues and restricted plants to living near bodies of water. Some plants evolved root-like structures that were mostly for anchoring a plant in place, but also took in some water.
It wasn’t until an additional 50 million years after the move on to land that true roots evolved, and these are very effective at getting the resources essential for photosynthesis and survival. In fact, the evolution of true roots 400 million years ago is associated with the worldwide reductions in carbon dioxide, since more resources could be gathered by roots for photosynthesis. Importantly, plants were no longer tied to bodies of water!
Large roots anchor a plant in place.
Tiny root hairs on a bulb take up nutrients when moisture is present.
Water issues continued, however, even with true roots. Early roots were very thick and could not efficiently search through the soil for resources. So plants either evolved thinner roots, or formed beneficial associations with very tiny fungi (called mycorrhizal fungi) that live in the soil. These fungi create very thin, root-like structures that allow for more effective resource uptake. In general, while life on land is hard, plants have evolved ways to cope via their roots.
Students in the Chicago Botanic Garden and Northwestern University Program in Plant Biology and Conservation were given a challenge: Write a short, clear explanation of a scientific concept that can be easily understood by non-scientists. This is our second installment of their exploration.
Peter DeJongh is a first-year master’s student studying land management and conservation in the graduate program at Northwestern University and the Chicago Botanic Garden. His academic focus is on developing strategies to optimize plant and wildlife conservation and restoration. He aims to work in applied conservation or environmental consulting upon completion of his degree.
