KALAHEO, Kauai – An endangered Kauai plant has not been seen in nature for the past decade, but a local biologist is trying to brighten its future through a breeding program borrowed from zoos.

Kauai locator map

‘Alula, also known as ‘olulu or “cabbage on a stick,” is endemic to Kauai and the neighboring island of Niihau. Several wild populations have been documented on Kauai, but the last known specimen died on the island’s Na Pali Coast sometime after 2012.

Seana Walsh, a conservation biologist at the National Tropical Botanical Garden headquartered on the South Shore, said NTBG personnel hunted for the isolated specimen in 2020 but didn’t find it after multiple drone surveys of where it was last seen.

Now, she is getting ready to change the ‘alula’s status from “critically endangered” to “extinct in the wild” on the IUCN Red List, a resource that assesses the extinction risk status of animal, fungus and plant species throughout the world. But ‘alula’s change in Red List status, which will take effect by the end of the year, is not the final nail in the species’ coffin.

National Tropical Botanical Garden personnel outplant hundreds of alula on Kauai. The species is scheduled to be declared extinct in the wild.
National Tropical Botanical Garden personnel plant hundreds of ‘alula on Kauai. The species is scheduled to be declared extinct in the wild. Courtesy: Seana Walsh/2022

‘Alula specimens exist in botanical collections across the globe, and the plant is notably popular among commercial growers throughout Europe, where it is often misleadingly billed as “volcan palm.”

The ‘alula’s unbranched stem is topped by a cluster of vibrant and fleshy leaves, lending it the appearance of a small palm tree often perched on seaward cliffsides. The plant, which is on the federal endangered species list, exhibits trumpet-shaped cream or yellow flowers when in bloom.

Yet even as the scientific world assumes ‘alula no longer exists in the wild, Walsh, NTBG, the Chicago Botanic Garden, Botanic Gardens Conservation International and others are developing a resource that could grant B. insignis and other endangered plant species a new lease on life.

Alula, also known as olulu or "cabbage on a stick," is inbred in collections throughout the world. Increased genetic diversity may increase the plant's odds of successful reintroduction in the wild.
‘Alula, also known as “cabbage on a stick,” is inbred in collections throughout the world. Increased genetic diversity may increase the plant’s odds of successful reintroduction in the wild. Courtesy: Seana Walsh/2022

The researchers’ project, funded by a National Geographic Society grant, is a “plant studbook” – a botanical version of a system developed by zoos breeding critically endangered animals, to return remaining diversity to the primary collection at NTBG and test reintroduction techniques near the known historic range of this species.

The botanic garden community has relied on seed banking as a way to preserve plants, said Kayri Havens, a senior director of ecology and conservation at Chicago Botanic Garden.

“Because of that, we hadn’t focused so much on how you maintain living collections,” he said. “It was through discussions with our colleagues in the zoo community that we came to realize there were things we could be doing with plants that we can’t seed bank.”

Seeds placed into banks are stored in dry, cold conditions, where many can remain viable for centuries.

Perhaps the world’s most famous seed bank is the Svalbard Global Seed Vault, located on a Norwegian archipelago in the Arctic Ocean. The Svalbard vault, which houses more than 4,000 species of seeds, can hold a maximum of 2.25 billion seeds in total.

But 20-30% of flowering plants – including B. insignis – cannot be seed banked, either because they do not produce enough seeds, or the seeds they make cannot withstand drying or freezing.

“We call those plants ‘exceptional plants,’” Havens said. “We maintain them in living collections, and that’s where the zoo pedigree approach really comes into play.”

The ‘alula is a critically endangered species and is one of 38 Red List species with fewer than five individuals remaining. International Union for Conservation of Nature

Zoos track endangered animals held in collections throughout the world. They then use a genetic analysis program called PMx to make crosses that minimize the loss of genetic diversity in their “ex situ meta-collection” – a term for all individuals of a given species held in every zoo on Earth.

In layperson’s terms, it’s a procedure performed to avoid inbreeding, which increases the chances of inheriting “bad genes.”

Such controls aren’t necessary for plants or animals belonging to species with healthy population numbers. But the chances of inbreeding increase exponentially when dealing with endangered species like ‘alula, which have tiny gene pools.

Yet historically, botanic gardens haven’t taken this into account.

“We often don’t control breeding. We just let plants cross in our collection: either they self-pollinate, or pollinators visit them, or they’re pollinated by wind, and we just collect whatever fruits come along,” Havens said.

Inbreeding is nearly impossible to prevent among collections with 50 or fewer individuals, according to Havens’ colleague Jeremie Fant – and there are very few collections of B. insignis with more than 50 individuals.

“This meta-collection idea is imperative if we are to save the plants, not only to conserve genetics, but to avoid that inbreeding problem,” Fant said. “Very few collections of any plant are ever large enough to prevent inbreeding.”

This means videos of greenhouses filled with ‘alula in Europe, and the domestic plants found throughout Hawaii, belie the species’ genetic rarity. They are all inbred, to one degree or another.

For about a decade, Walsh, Havens, Fant and others have been eyeing Kauai’s own B. insignis as a case study for a plant studbook.

Walsh identified three genetically distinct groups among ‘alula scattered around the world at the same time Chicago Botanic Garden personnel were chatting with colleagues in the zoological field.

Northwestern University graduate student Jeremy Foster (left) bred 18 cross-types of alula using four pollen sources identified by Kauai biologist Seana Walsh
Northwestern University graduate student Jeremy Foster, left, bred 18 cross-types of ‘alula using four pollen sources identified by Kauai biologist Seana Walsh. Courtesy: Seana Walsh/2022

Eventually, the team reached out to botanic gardens to request pollen, using their studbook to see if crosses between collections that were less related to one another resulted in progeny that were less inbred and healthier.

They acquired pollen from NTBG, the United States Botanic Garden, University of California Botanical Garden and the San Diego Zoo to cross with plants at Chicago Botanic Garden. Each institution’s collection originates from specimens collected by longtime NTBG research biologist Ken Wood during the 1980s and ‘90s, before damage caused by 1992’s Hurricane Iniki spelled the beginning of the end for ‘alula in the wild.

A graduate student at Northwestern University then bred 18 cross-types from the four pollen sources, collected their seeds and mailed them to NTBG, which began growing them on Kauai this year.

Walsh and her colleagues first looked for the effects of cross-type on seed germination – “If they were more inbred, was there less germination?” – before monitoring survivorship among seedlings transferred to NTBG’s nursery.

This past summer, about 420 ‘alula seedlings passed out of the nursery and into plots located within NTBG’s McBryde and Limahuli gardens on Kauai’s South and North shores.

Walsh is now routinely monitoring these plants for survivability and growth. It can be a time-consuming process: at the six-month mark this October, she will use a set of calipers to measure the height, width and number of leaves on each surviving plant.

But the countless hours spent by researchers in laboratories, nurseries and garden plots in Chicago and Kauai may do more than write the blueprint for an international plant studbook. They may also result in ‘alula’s reintroduction to the natural landscape of Kauai.

“We’re going to have to do a lot of in situ work to really try to get this species back in the wild,” Walsh said. “This is one part of it: trying to increase diversity in progeny to get more vigorous plants that have the capability to adapt to the changing environment they’re now faced with.”

Civil Beat’s coverage of climate change is supported by the Environmental Funders Group of the Hawaii Community Foundation, Marisla Fund of the Hawaii Community Foundation and the Frost Family Foundation. 

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