Botanist Steve Perlman rappels into the Kalalau Valley, a biodiversity hotspot on the Hawaiian island of Kauai.

Botanist Steve Perlman rappels into the Kalalau Valley, a biodiversity hotspot on the Hawaiian island of Kauai.Courtesy of Bryce Johnson/FLUX Hawaii

Extreme Botany: The Precarious Science of Endangered Rare Plants

They don’t make the headlines the way charismatic animals such as rhinos and elephants do. But there are thousands of critically endangered plants in the world, and a determined group of botanists are ready to go to great lengths to save them.

To save plants that can no longer survive on their own, Steve Perlman has bushwhacked through remote valleys, dangled from helicopters, and teetered on the edge of towering sea cliffs. Watching avideoof the self-described “extreme botanist” in action is not for the faint-hearted. “Each time I make this journey I’m aware that nature can turn on me,” Perlman says in the video as he battles ocean swells in a kayak to reach the few remaining members of a critically endangered species on a rugged, isolated stretch of Hawaiian coastline. “The ocean could suddenly rise up and dash me against the rocks like a piece of driftwood.”

When he arrives at his destination, Perlman starts hauling himself up an impossibly steep, razor-sharp cliff 3,000 feet above the sea without a rope, his fingers sending chunks of rock tumbling down to the waters below. Finally, he reaches the plants and painstakingly transfers pollen from the flowers of one to those of another to ensure that the species can perpetuate itself. At the end of the season, he will return to collect any seeds they were able to produce.

Among the plants for which Perlman, a rock-star botanist with theUniversity of Hawaii’s Plant Extinction Prevention Program,一再冒着生命的风险杨氏侵袭, better known as cabbage-on-a-stick. One of the strangest-looking species in the Hawaiian flora, with a thick, swollen stem crowned by a rosette of fleshy leaves resembling a head of cabbage, it typically reaches 3 to 6 feet high but has been known to grow up to 16 feet tall. The plant once dotted seaside precipices on two Hawaiian islands, including the spectacular fluted cliffs of Kauai’s Nā Pali coast. But feral goats, rats, and invasive weeds brought to the islands by Polynesians and, later, Europeans decimated the species. What’s more, by the 1970s scientists had come to suspect that it had lost the large moth that they believe once fertilized its fragrant, creamy yellow, trumpet-shaped flowers. Without its pollinator, the plant was unable to produce seeds and its future in the wild was doomed. Had Perlman not come to the rescue, the plant would have faced almost certain extinction.

“When only a few members of a plant species remain, you need to make sure that every little bit of genetic diversity is preserved.”

The fate of cabbage-on-a-stick is now in the hands of another group of emergency botanists. Jeremie Fant, the head of Chicago Botanic Garden’s conservation genetics lab, and his colleagues are experimenting with procedures first developed at zoos to perform high-tech genetic rescue, including the development of a “studbook” that documents the pedigree of surviving individuals of the imperiled species in order to make last-ditch cross-breeding programs possible.

“When only a few members of a plant species remain,” says Fant, “you need to make sure that every little bit of genetic diversity is preserved.”

像Perlman和Fant这样的科学家在最后一条植物学的刀边缘工作,以节省诸如卷心菜般的危险植物,因为这些物种无法自行生产足够的种子。植物保护在很大程度上依赖种子库。理想情况下,种子是从野生种群中策略性收集的,以确保已经捕获了物种的遗传多样性。但是,大量植物是所谓的特殊物种,在常规种子库中无法保存。有些是如此罕见,以至于他们患有近亲繁殖和其他遗传疾病,这些疾病阻碍了繁殖,并且没有产生足够的种子来存放。有些生产“顽固”种子,因为它们无法生存在干燥和冷冻的情况下,因此无法存储在种子库中。

The plant known as cabbage-on-a-stick (Brighamia insignis) has been grown at Limahuli Garden & Preserve on Kauai, which is within the historic range of the species.

The plant known as cabbage-on-a-stick (杨氏侵袭)has been grown at Limahuli Garden & Preserve on Kauai, which is within the historic range of the species.Seana Walsh

According to Valerie Pence, director of plant research at the Cincinnati Zoo & Botanical Garden’sCenter for Conservation & Research of Endangered Wildlife, a conservative estimate is that about 9 percent of threatened species fall into this category. If,as some scientists suspect, as many as one-third of the 500,000 plants believed to exist on earth are at risk, that means that 15,000 exceptional plants could require the kind of botanical intensive care that Perlman and Fant have provided for cabbage-on-a-stick.

便士开创了另一个紧急植物学领域,开发了许多特殊植物的体外繁殖方案,并将其保存在她所谓的“冷冻花园”中的深度冻结中。但是,她说:“关键是,有很多物种需要除传统种子银行以外的其他方法,而其中一些方法需要额外的劳动,设施和专业知识,因此更昂贵。问题是我们将如何应对这个挑战?”

Among the planet’s exceptional plants are not just rare island endemics like cabbage-on-a-stick, but evolutionary relicts such as cycads, palm-like plants with stout trunks, arching crowns of stiff, evergreen leaves, and a 300-million-year lineage, older than any other surviving complex life form. They also include a variety of ecologically and economically important plants around the globe, from oaks and conifers to pawpaws and palms.

如今,在野外只有一只孤独的菜单植物生存。它在夏威夷岛考艾岛,无法繁殖。

To ensure the health of their animal populations, zoos and aquariums have for decades engaged in a kind of collaborative family planning. The first studbook created for conservation purposes was set up in 1932 for the European bison. Today, according to Kristine Schad, director of the Association of Zoos and Aquariums’Population Management Center,在组织成员的护理中,鞋带是500多种动物的“物种生存计划”的组成部分,该组织代表了美国和国外的230多个机构。每个物种的书籍都包括有关世界各地动物园和水族馆中各自动物的信息,例如他们的住所,父母是谁,祖先来自野外的地方,无论是以前繁殖,如果是的话,和谁一起。

Genetic and population analyses assist with the matchmaking, helping the institutions determine which animals should be bred with each other to ensure that populations are stable, inbreeding is avoided, and all the lineages present in the collective gene pool are preserved in living animals. The goal is to secure stable and genetically diverse populations for the future, and in many cases, to increase the number of animals to replenish depleted populations in their natural habitats.

Some 40 years ago, when Perlman set out to save cabbage-on-a-stick, a couple of hundred plants still grew on the Hawaiian island of Kauai. But two hurricanes destroyed most of them, and today, one lone individual is believed to survive in the wild, unable to reproduce.

A botanist collects pollen from the flower of Brighamia insignis.

A botanist collects pollen from the flower of杨氏侵袭.National Tropical Botanical Garden

然而,该物种比许多灭绝的植物更幸运,因为由于佩尔曼的努力,它已经被培养了。佩尔曼能够从15种不同的植物中伸展并收集种子。这些繁殖是繁殖的,现在数百个标本在夏威夷国家热带植物园运营的各个地点生长,包括利马胡利花园,在纳帕利海岸沿该物种的自然栖息地附近。这些植物的后代在全球至少57个植物园中也发现了。此外,近年来,荷兰的商业托儿所在近年来已经繁殖并销售了数十万个标本。佩尔曼说,随着许多植物的耕种,卷心菜“在我的一生中不会灭绝”。

Recently, however, it became apparent that the National Tropical Botanical Garden’s cabbage-on-a-stick plants were not producing seeds as readily as they once did. Fant and his colleagues decided to help figure out why. Using a database managed byBotanic Gardens Conservation International(BGCI) that includes plant records from about 1,500 of the more than 3,000 botanic gardens worldwide, they tracked where else cabbage-on-a-stick is growing in cultivation. They obtained plants from a number of botanic gardens in North America and Europe, did genetic testing, and discovered that some of the lineages once present in the Hawaiian garden’s plants had been lost. Apparently, the plants were beginning to suffer the effects of inbreeding.

The good news, according to Fant, is that the genetic sampling also found that much of the missing genetic diversity was present in plants at botanic gardens in Berkeley, Chicago, San Diego, and Switzerland, all of which trace their origins to the seeds Perlman collected. “There were six or seven individuals that could be bred back into the National Tropical Botanical Garden plants” to restore genetic diversity, increase seed production, and improve the species’ prospect for long-term survival, he says.

A scientist with the Plant Extinction Prevention Program climbs through remote Hawaiian ecosystems to study endangered plant species.

A scientist with the Plant Extinction Prevention Program climbs through remote Hawaiian ecosystems to study endangered plant species.PEPP

Over the past few decades, botanic gardens have taken the lead in efforts to save imperiled plants by creating a backup system in cultivation as a hedge against extinction in the wild. They not only have collected seeds and pollen for safeguarding in seed banks, but also have spearheaded efforts to propagate the species and reintroduce them to their natural habitats. Specialized botanic gardens such as Pence’s in Cincinnati are developing species-specific protocols for preserving a growing number of exceptional plants, including cryopreservation of embryos and other vegetative tissues in a state of suspended animation in liquid nitrogen at -321 degrees Fahrenheit.

One thing botanic gardens haven’t done, says Fant, is see plants as distinct individuals. “Zoos manage their animals as individuals,” he says, “but plants are usually maintained as a collection and rarely is any one individual perceived as a unique member of that species.” This has hindered efforts to save them. Without a studbook tracking the complete pedigree of each genetically unique cabbage-on-a-stick plant in cultivation, for example, it was impossible to ensure that no lineages were being lost. This, Fant and his colleagues wrote in a2016 paperin the美国植物学杂志, “is clearly not a sustainable solution to managing the thousands of threatened exceptional plant species” held at botanic gardens around the globe.

“We need an eharmony for plants,” says Abby Meyer, executive director ofBGCI in the U.S., referring to the popular online dating site. Meyer has proposed such a botanical matchmaking system, which she calls “integrated collections management.” Like the collaborative system employed at zoos, it would enable gardens to take into account the plants they grow as well as those at other institutions when making decisions about new plants to acquire, crossbreeding, and other measures to preserve the health and diversity of the plants in their care.

Given the grim state of plants around the globe, there’s no time to lose. Currently, says Craig Hilton-Taylor, head of the International Union for Conservation of Nature’sRed Listof imperiled species program, 2,787 plants are considered “critically endangered,” defined as suffering “an extremely high risk of extinction.” In many cases, fewer than 50 individuals remain in the wild, putting these plants in a category known in bureaucratic parlance as “CR-D” species. Meyer points out that among these rarest-of-the-rare plants are 43 U.S. native trees, giving the country the dubious distinction of being tied for second place with Madagascar, behind China, as the country with the most CR-D trees.

植物保护尚未产生与动物保护的几乎相同的紧迫感,也没有产生资金。

According to Hilton-Taylor, in addition to the critically endangered species, 4,269 plants on the Red List are deemed endangered, with “a very high risk of extinction,” and another 5,725 are considered vulnerable, facing “a high risk of extinction” in the wild. Because to date only 8 percent of known plant species have been assessed for inclusion on the Red List, these numbers are certain to rise.

为了使问题更加不稳定,只有41%的已知全球威胁物种在植物园的种植中受到保护,据迈耶(Meyer)称,许多物种仅在一个机构中被拘留。她指出,仅在一个花园中发现了三分之一的北美本土威胁物种,使它们面临害虫,疾病,风暴和其他灾难的危险。

Yet plant conservation has not generated nearly the same sense of urgency — nor the funding — that animal conservation has. In the U.S., for example, plants receivejust 5 percentof federal dollars spent on species conservation.

A male Wood’s cycad, Encephalartos woodii, of South Africa. The species survives today only in cultivation.

A male Wood’s cycad,Encephalartos woodii,of South Africa. The species survives today only in cultivation.凯皇家植物园

In 1999, American biologists James Wandersee and Elisabeth Schussler coined the term “plant blindness”描述人类无法欣赏植物的生态和经济重要性,甚至注意到周围的植物。植物学家还归咎于我们缺乏同情植物,因为我们未能应对他们面临的威胁。考虑到,由于其美丽和古老的血统而被植物收藏家垂涎的苏铁,遭受了与犀牛,大象和其他所谓的超凡魅力的大型巨型巨星相比,全球偷猎危机遭受的危害更糟。结果,有75%的苏联物种有灭绝的风险,但它们的困境甚至都不是公众雷达屏幕上的束缚。

That is certainly not true for beloved animals. For example, when the mate of Tashi, a female rhino at the Buffalo Zoo, passed away, the zoo teamed up with Cincinnati’s Center for Conservation & Research of Endangered Wildlife, which for 10 years had been storing the sperm of Jimmy, a male Indian rhinoceros who had never sired a calf during his lifetime. Jimmy’s sperm was rushed to Buffalo to inseminate Tashi. Sixteen months later, in 2014, the birth of the baby rhino named Monica, conceived through artificial insemination to perpetuate the DNA of a bull that had been dead for a decade, was big news.

While beleaguered rhinos like Jimmy regularly make headlines, there are few heart-wrenching stories about plants like the male Wood’s cycad,Encephalartos woodii,of South Africa, the only member of his species, male or female, ever to be found alive. Today, he survives only in cultivation. Unlike Jimmy the rhino, the handsome cycad, with orange cones and a crown of bright green, 6- to 10-foot-long leaves, has no pet name. And unlike Jimmy, his species will never again reproduce and evolve freely in the wild.