Scientific Resurrection: Bringing Extinct Plants Back from the Dead

Species in the hibiscus and sedge families, both extinct for decades but preserved at the Missouri Botanical Garden, are among those scientists want to target to bring back from the dead.

Scientists from across the globe recently collaborated to create a list of plants targeted for “de-extinction.” They examined plant specimens preserved in herbaria, or collections of dried plants, looking for seeds suitable for growing new plants. They considered the age of the specimen and uniqueness of species to create a list of top candidates.

Sphaeralcea procera (Malvaceae) and Eleocharis brachycarpa (Cyperaceae), both species housed in the Garden’s Herbarium, made the top 25.

“The study highlights the incredible value of collections in herbaria and how material on specimens can potentially be used to reverse the ongoing loss of biodiversity,” said Matthew Albrecht, Interim Director of the Garden’s Center for Conservation and Sustainable Development.

^{An array of plant specimens from the Missouri Botanical Garden’s Herbarium. With more than 7.5 million specimens, the Garden’s Herbarium is one of the largest in the world. Photo by Marissa Billmeyer.}

The List

Scientists at Roma Tre University in Rome started this groundbreaking work by developing a list of 556 extinct plant species in herbaria across the globe and reaching out to those institutions to see if their specimens included preserved seeds.

The Missouri Botanical Garden, which houses one of the largest herbaria in the world with more than 7.5 million preserved plant specimens, was an obvious candidate. The group sent Albrecht, whose research focuses on North American plants on the brink of extinction, a list of 51 species in the Garden’s Herbarium in hopes of finding seeds. Of the 51 species, Albrecht found 12 Herbarium specimens included seeds.

^{A specimen of Condylocarpon glabrum, an extinct species in the dogbane, in the Garden’s Herbarium. Specimens with attached envelopes often contain fruits or seeds of the plant, which made searching the physical specimen itself, and not just a digitized version, essential. Photo courtesy of TROPICOS.}

Species with seeds included two from North America, as well as species from Madagascar, South America, and other areas where the Garden has conducted research.

The Rankings

In total, scientists identified 161 species in 60 herbaria worldwide with seeds that could be propagated. By factoring age, resilience in storage, and evolutionary uniqueness, they gave each a “de-extinction” score and identified the top 50 candidates.

Sphaeralcea procera is ninth on the list. This New Mexico native perennial herb is also known as the Luna County globemallow and produces purplish-pink flowers that resemble those of cultivated hibiscus. It was last observed in the wild in the 1940s.

^{A specimen of Sphaeralcea procera, a member of the hibiscus family also called Luna County globemallow, collected in 1943 and house in the Garden’s Herbarium still contains potentially viable seeds.. Photo courtesy of TROPICOS.}

The Garden’s specimen is 80 years old, on the younger-end of those on the “de-extinction” list. Specimen age is important, Albrecht explained, because earlier preservation techniques sometimes included use of DNA-damaging chemicals, which potentially can kill any living seed on a specimen. Now, scientists freeze specimens before placing them in the herbarium.

Eleocharis brachycarpa, No. 25 on the list, is a much older specimen at 187. However, it scored relatively high for evolutionary distinctiveness, as this genus is evolutionarily and morphologically unique compared to other members of the sedge family. Members of Eleocharis produce highly reduced leaves and photosynthesis occurs primarily in green photosynthetic stems. Also known as short-fruited Spikerush, this small, annual herbaceous plant is grass-like in appearance and known only from marshes or wetlands in Texas and Mexico.

^{The Garden’s specimen of Eleocharis brachycarpa, in the sedge family, is nearly 190 years old but still contains seeds that could be germinated to grow new plants of the extinct species . Photo courtesy of TROPICOS.}

Next Steps Toward Resurrection

The study has considerable implications on conservation, its authors say, providing tools and guidance for resurrection of extinct plants. But Albrecht said that next steps is likely years away.

Scientists must develop methods and protocols for extracting seeds from delicate Herbarium specimens and germinating them. Before scientists begin working with the species on the candidate list, they must first perfect methods for germinating seeds of closely-related species that are not extinct.

^{The Garden’s Seed Bank, started in 2013, stores thousands of seeds including rare and endangered species. Seed banking is a more modern method of seed preservation and valuable conservation tool that enables the long-term storage of genetic diversity of a large number of plant species. Photo by Demi Striglos.}

The seeds of the extinct species, of course, are highly valuable to biodiversity as they are the only hope for its future. Unlike methods considered for animal de-extinction, which can splice ancient animal DNA with that of close living relatives or selective back-breeding, seeds or spores are the only way to scientifically resurrect extinct plants, Albrecht explained.

All herbarium specimens, even those without seeds, contain DNA from the plant. That DNA can be used for other important scientific purposes, like determining genetic variability of a species or taxonomic identification. But it can’t regenerate plants.

“With plants, you can take spores and seeds and germinate them,” Albrecht explained.

If the herbarium seeds are found to be viable, it brings up another important scientific question: is a species really extinct if living seeds remain?

“That opens a whole different avenue of conservation with plants,” Albrecht said.

^{Botanical gardens sometimes conserve extinct-in-the-wild species by maintaining them in their living collections. The world’s smallest water lily, Nymphaea thermarum, is extinct in the wild but can be found in the Garden’s Climatron. Adding truly extinct species resurrected from Herbarium specimens would be a new step in conservation horticulture. While possible, that is likely years away. Photo by Tom Incrocci.}

Moving into the Future

The study is the latest example of evolving uses of herbaria.

While perhaps not as formally kept, herbaria have been around for centuries as people have been collecting and pressing plant specimens for more than 500 years. In their earliest days, these specimens were used as winter teaching aids for training doctors. As plant science evolved, herbaria were used for taxonomy and describing new-to-science plant species.

Today, the world’s herbaria contain well over 300 million specimens that serve as a verifiable record of botanical life on the planet, said Garden Herbarium Director Jordan Teisher. And, thanks to modern technology, many are accessible via online databases.

“The size and diversity of this collection, coupled with global efforts to make the associated data available and searchable digitally, has opened exciting new research directions unforeseeable to the men and women who began the noble tradition of identifying and recording the plant life that surrounds and sustains us,” Teisher said. “Most critically in our rapidly changing climate and landscapes, herbarium specimens allow us to set benchmarks for measuring biodiversity loss, build our knowledge of species diversity and distributions, and establish meaningful and effective conservation priorities.”

^{Visitors at the Grand Opening of the Jack C. Taylor Visitor Center help digitize Herbarium specimens. Digital specimens have opened up many new research possibilities. Photo by Kat Niehaus.}

Some new research also questions long-held rules for using specimens. For instance, scientists try to minimize damage to specimens as much as possible, but removing seeds for germination would of course irrevocably change the specimen. But exceptions can be made in the interest of advancing essential research, Teisher said.

“When we get requests to remove material from specimens, we ask whether the material could be acquired elsewhere, how ground-breaking and time-sensitive the project is, and what the importance of the specimens is for other purposes,” he said. “For example, we would not let you take a leaf from a specimen collected by Darwin unless you had a really, really good reason.”

Resurrecting a species from extinction certainly seems like a reason Darwin himself would support.

Catherine Martin
Public Information Officer