Recent studies have shed light on the survival of cycads, ancient plants from the Mesozoic Era, highlighting their unique symbiotic relationship with nitrogen-fixing bacteria. This research offers new understanding of the ecological evolution and climate adaptability of these plants.
Originating from the Mesozoic Era, cycads were once widespread but are now largely extinct, except for a few species in tropical and subtropical regions. These surviving species depend on a symbiotic relationship with bacteria for nitrogen fixation, unlike their extinct relatives.
Cycads, a prime food source for dinosaurs, thrived during the Mesozoic Era, about 252 million years ago. These plants were abundant in the forest understory, supporting various prehistoric creatures. Today, only a limited number of these palm-like species exist in tropical and subtropical environments.
Cycad Extinction and Persistence
The extinction of most cycad species mirrors the fate of the dinosaurs they once fed. Their decline started in the late Mesozoic and continued into the early Cenozoic Era, exacerbated by events like the asteroid impact and volcanic eruptions at the K-Pg boundary 66 million years ago. However, unlike the dinosaurs, some cycads managed to survive until today.
A cycad fossil was analyzed for nitrogen isotopes to determine the environment it grew in. Credit: Michael Kipp – Duke University
Recent Discoveries on Cycad Endurance
Published today (November 16) in Nature Ecology & Evolution, a new study reveals that surviving cycad species developed a symbiotic relationship with bacteria in their roots for nitrogen acquisition. Similar to modern legumes, these cycads exchange sugars for nitrogen extracted from the atmosphere by the bacteria.
Lead researcher Michael Kipp’s interest in nitrogen-fixing plants stems from their ability to record atmospheric composition. His work, which began during his Ph.D. at the University of Washington, involved analyzing ancient plant fossils. He discovered that nitrogen-fixing was not a trait of extinct cycad species, but only of surviving ones.
A fossilized veined leaf from the same layer as an extinct cycad was examined for nitrogen isotope comparison. Credit: Michael Kipp – Duke University
Kipp, who spent nearly a decade on this research, first at the University of Washington and then as a postdoctoral researcher at Caltech, realized that these findings were more about the plants’ ecological evolution than atmospheric conditions. He joins Duke University’s faculty this year as an assistant professor of Earth and Climate Sciences in the Nicholas School of the Environment, continuing his work with fossils to understand Earth’s climate history and future.
Research Methods and Discoveries
Kipp applied chemical analysis techniques, typically used for ancient sea life and sediments, to terrestrial plants. This approach was novel, and Kipp faced challenges in refining the method and acquiring rare plant fossil samples.
He found that younger fossil samples (about 20-30 million years old) from surviving cycad lineages showed nitrogen signatures indicative of symbiotic bacteria, similar to present-day cycads. However, this signature was absent in older, extinct cycad fossils.
Implications and Future Research Directions
It’s still uncertain how nitrogen fixation aided the surviving cycads. It might have helped them adapt to climatic shifts or compete with rapidly growing angiosperm plants after the mass extinction. Kipp views this technique as a promising avenue for further research.
This study received funding from The Paleontological Society, the University of Washington Royalty Research Fund, and a NASA Exobiology grant.
Reference: “Nitrogen Isotopes Reveal Independent Origins of N2-Fixing Symbiosis in Extant Cycad Lineages,” Michael A. Kipp et al., 16 November 2023, Nature Ecology & Evolution.
DOI: 10.1038/s41559-023-02251-1
Table of Contents
Frequently Asked Questions (FAQs) about cycad survival research
What are cycads and where did they originate from?
Cycads are ancient plants that originated during the Mesozoic Era. They were once widespread but now mostly exist in tropical and subtropical areas.
How did cycads survive extinction?
Cycads survived by forming a symbiotic relationship with nitrogen-fixing bacteria, a trait that helped them adapt to changing climates and was not present in their extinct counterparts.
What was the role of cycads during the Mesozoic Era?
During the Mesozoic Era, cycads were a primary food source for grazing dinosaurs and other prehistoric animals, thriving in the forest understory and contributing to the ecosystem.
How were the study’s findings about cycad survival determined?
The study, published in Nature Ecology & Evolution, analyzed fossilized cycad specimens for nitrogen isotopes, revealing a symbiotic relationship with nitrogen-fixing bacteria in their roots.
What implications does this research have for understanding plant evolution and climate change?
The research offers insights into the ecological evolution of cycads and their ability to adapt to past climate changes, providing a window into plant survival mechanisms and the history of Earth’s climate.
More about cycad survival research
- Cycads and Nitrogen Fixation
- Mesozoic Era Plant Life
- Cycad Survival and Extinction
- Nitrogen Isotope Analysis in Cycads
- Symbiotic Relationships in Plants
- Climate Adaptation of Ancient Plants
- Earth’s Climate History and Plant Evolution
4 comments
wow, i never knew cycads were so interesting? It’s like they’ve been around forever and still kicking, kinda cool they survived when so many others didn’t.
Not sure if I got it right but is it like the cycads had their own way of getting nitrogen from the air with the help of bacteria? that’s some sci-fi stuff right there.
A bit confusing with all the scientific terms, but it’s fascinating to see how plants have evolved over millions of years. It’s like a glimpse into the past, you know?
so these plants were dino food? kinda makes you think about how everything’s connected, from the smallest bacteria to the biggest dinosuars. nature’s amazing.