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PHOTO: Peter DeJonge.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.

DIAGRAM: Janzen-Connell hypothesis.

PHOTO: This Malaysian silverleaf monkey eats fruit as part of its diet, dispersing seeds far beyond the canopy line.

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.

Garden post-grads and scientists are in the field working on restoration efforts in the Colorado plateau, fossil hunting in Mongolia, and filming videos on sphinx moths. Interested in our graduate programs? Join us. 


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.

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Simulating Summer in the Plant Science Center

Getting seeds to reveal their secrets

Andrea Kramer —  February 25, 2013 — Leave a comment
Seeds of potential native winners from the Colorado Plateau.

Seeds of native species from the Colorado Plateau.

These seeds may not look like much right now, but the story they tell is full of adventure and promise. This week we are simulating summer in the Daniel F. and Ada L. Rice Plant Conservation Science Center to get them to reveal some of their secrets.

My research takes me to the Colorado Plateau (you may know it as the “four corners” region), which is one of the most starkly beautiful places in the United States. I work with many Garden scientists, graduate students, and public land management agencies like the Bureau of Land Management (BLM) to carry out research that helps make native plant restoration and management on public lands throughout the Colorado Plateau as efficient and effective as possible. We are particularly focused on understanding how to help native plants cope with encroaching invasive species, changing land use, and shifting climates.

So these seeds come from a gorgeous place. But more importantly, they were produced by some pretty impressive native plants that were tough enough to not only survive last year’s crazy weather, but to also flower and produce seeds in some pretty harsh sites. Like Chicago, the Colorado Plateau experienced one of the hottest, driest summers it has seen in a long time. Most of the plants in the Colorado Plateau sat out the flowering season last year — they conserved their resources for a better year. We are interested in the plants that braved really bad conditions to produce seeds, because we think they will be especially useful when restoring habitat that has been badly damaged by wildfire or invasive species. We call these plants native winners.

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Unfortunately, very little is known about what makes these native winners tick. Our research is helping to uncover some of their secrets. Alicia Foxx (a student in our joint graduate program with Northwestern University) and I have just set up an experiment that will reveal the specific seed germination requirements for these native winners. We are using incubators that allow us create spring- and summer-like conditions that will tell us when and why seeds of these species are able to germinate and grow. Knowing this information is just a first step in our research that will help us improve the outcome of restoration practices.


©2013 Chicago Botanic Garden and my.chicagobotanic.org