Boise State scientist co-authors landmark study on the world’s most irreplaceable plants

Key Statistics at a Glance
Flowering plant species given an EDGE score	335,497
EDGE list priority species (globally threatened + evolutionarily distinctive)	9,945 (21.2%)
EDGE.List species documented in Flora of the World (FotW)	229 (2.3% of EDGE.List)
Highest EDGE rank documented in FotW	#2 - Amorphophallus lewallei (CR)
Evolutionary history (ED) captured in FotW	44,773.2 Myr (4.4% of total angiosperm ED)
Most evolutionarily distinct species in FotW	Amborella trichopoda (the most basal flowering plant species endemic to New Caledonia) - 139 million years
Extinct-in-the-Wild EDGE species in FotW	4 species

A new study published in Science by Forest et al. (2026) provides the first comprehensive assessment of Evolutionarily Distinct and Globally Endangered scores (called EDGE scores for short) for all 335,497 known flowering plant species. The work, a collaboration lead by the Royal Botanic Gardens, Kew, Zoological Society of London, and partners worldwide, reveals that more than a fifth (21%) of flowering plant evolutionary history is currently at risk of extinction - nearly double that of jawed vertebrates.

Among the contributors to this international effort is Professor Sven Buerki, Davidson Endowed Chair of Botany at Boise State. Buerki was a member of Félix Forest's research group at the Royal Botanic Gardens, Kew, where he helped lay the foundations for this work. He brings this global collaboration directly to Idaho - and to the Flora of the World (FotW for short) platform, where the study's findings are currently translated into accessible, open conservation data.

From the full dataset, 9,945 species form the EDGE list: plants that combine high evolutionary distinctiveness with serious extinction risk - the world's most irreplaceable species. Boise State's role in connecting this priority list to FotW is a direct expression of the conservation mission funded by the Davidson Endowment.

From gymnosperms to flowering plants: A decade of collaboration

Buerki's involvement in the EDGE programme predates this Science paper. In 2018, he was last author on a foundational study published in Scientific Reports that produced the first EDGE scores for gymnosperms - the conifers, cycads and their relatives - in collaboration with Forest and international colleagues. That paper identified the most evolutionarily distinct and threatened gymnosperms outside the flowering plants, and established the analytical framework that has since been applied, at far greater scale, to all 335,497 angiosperms - flowering plants - in the current work.

The progression from gymnosperms to flowering plants reflects a decade-long international partnership between Boise State University and the Royal Botanic Gardens, Kew - one of the world's leading plant science institutions. That partnership is now producing tangible conservation outcomes.

What are EDGE scores and evolutionary distinctiveness?

Evolutionary Distinctiveness (ED for short) measures how isolated a species is on the tree of life - how much unique evolutionary history it represents, expressed in millions of years (Myr). A species with high ED has few close relatives and has been evolving independently for an exceptionally long time. Losing it means losing an irreplaceable branch of the tree of life.

The EDGE score combines ED with extinction risk (from the International Union for Conservation of Nature Red List), producing a single metric that identifies the species most urgently in need of conservation attention. A high EDGE score signals both extraordinary uniqueness and imminent danger.

A striking example is Amborella trichopoda - a small shrub from New Caledonia whose lineage diverged from all other flowering plants approximately 130 million years ago. With an ED score of 139 Myr, it is the most evolutionarily distinct angiosperm in FotW, and its documentation on the platform ensures that scientists and conservationists can access its occurrence data alongside its evolutionary significance.

"More than two in five plant species are estimated to be threatened with extinction, yet fewer than 20% have formal threat assessments - compared to over 80% of vertebrate groups," said Professor Sven Buerki, the Dr. Davidson Endowed Chair of Botany at Boise State. "This makes it extremely difficult to prioritize plants for conservation. Our study provides a powerful framework to rank species for conservation action by combining their unique evolutionary history with extinction risk. It is the first time this approach has been applied to a group of this scale, and it will pave the way for other megadiverse groups such as insects."

Amborella trichopoda is one of the most evolutionarily distinct angiosperms. Photo credit: Christopher Davidson and Flora of the World.

"Our study provides a powerful framework to rank species for conservation action by combining their unique evolutionary history with extinction risk."

Professor Sven Buerki, Dr. Davidson Endowed Chair of Botany, Boise State University

Flora of the World documents 229 priority EDGE species

A key contribution of Buerki's work at Boise State has been to cross-reference the EDGE dataset against FotW's global occurrence database. The analysis reveals that 229 of the 9,945 EDGE list species (2.3%) are already documented in FotW - with specimen and observation records pinpointing exactly where these plants have been collected in the wild. These 229 species span remarkable diversity, from the Critically Endangered Amorphophallus lewallei of the Congo Basin (ranked 2nd globally for EDGE score) to island endemics like Ilex dimorphophylla from Japan's Ryukyu Islands.

In total, the FotW species with EDGE data collectively represent approximately 44,418 million years of angiosperm evolutionary history - 4.4% of all flowering plant ED on Earth. Among matched species, exceptional outliers stand out: Gomortega keule (78 Myr), the sole member of its family, survives in a single valley in Chile; and Cephalotus follicularis (76 Myr), a carnivorous pitcher plant from a single coastal habitat in Western Australia, represents one of the most isolated lineages in the plant kingdom.

Extinct in the Wild: The most urgent conservation cases

Among the EDGE.List species documented in FotW, four carry the most sobering designation on the International Union for Conservation of Nature Red List: Extinct in the Wild (EW). These are plants that no longer exist as self-sustaining populations in nature - their survival depends entirely on cultivation in botanical gardens, seed banks, and similar ex situ collections.

Brugmansia sanguinea are entirely extinct in the wild. Photo credit: Christopher Davidson and Flora of the World.

The Davidson Endowed Chair and Boise State's conservation mission

Buerki holds the Dr. Davidson Endowed Chair of Botany at Boise State University - a position created to advance plant science and conservation at Boise State and to build enduring partnerships with leading institutions worldwide. His involvement in the Forest et al. Science paper, and the subsequent implementation of EDGE scores in FotW, is a direct expression of that mission.

The 229 EDGE list species already documented in FotW represent a foundation for this integration. Expanding this coverage - and ensuring that EDGE scores and ED values are visible and accessible on the platform - is a concrete, ongoing goal of the work funded by the Dr. Davidson Endowment at Boise State.

"Our goal at Boise State is to make the results of this study directly visible in Flora of the World - so that anyone exploring a species page can see not just where a plant has been recorded, but how evolutionarily unique and how threatened it is," Buerki said.

"Our goal at Boise State is to make the results of this study directly visible in Flora of the World."

Professor Sven Buerki, Dr. Davidson Endowed Chair of Botany, Boise State University

As the Forest et al. study notes, protecting just 5.9% of species ranked by their EDGE score would safeguard half of all threatened angiosperm evolutionary history. Boise State's role - through the Dr. Davidson Endowed Chair and the Flora of the World collaboration - in identifying where those species occur and making that information openly accessible, places the university at the heart of global plant conservation strategy.

Top 25 EDGE.List species documented in Flora of the World

Species names link directly to their Flora of the World taxon pages. Threat status follows the IUCN Red List. ED = Evolutionary Distinctiveness (millions of years). P(ext) = median probability of extinction.

Rank	Species	Family	Threat	EDGE Score	ED (Myr)	P(ext)	FotW Records
#2	Amorphophallus lewallei	Araceae	CR	46.89	50.9	0.962	1
#11	Gomortega keule	Gomortegaceae	EN	38.01	78.4	0.485	4
#15	Lyonothamnus floribundus	Rosaceae	EN	31.66	65.3	0.494	1
#24	Petenaea cordata	Petenaeaceae	EN	28.84	57.3	0.501	5
#39	Ilex dimorphophylla	Aquifoliaceae	CR	27.13	32.7	0.954	1
#70	Nardostachys jatamansi	Caprifoliaceae	CR	24.99	26.8	0.932	5
#76	Afrothismia korupensis	Burmanniaceae	CR	24.19	28.6	1	3
#110	Pitavia punctata	Rutaceae	EN	19.27	41.7	0.5	3
#118	Cephalotus follicularis	Cephalotaceae	VU	18.42	75.6	0.244	1
#126	Lactoris fernandeziana	Aristolochiaceae	thr	17.75	74.4	0.267	3
#247	Magnolia stellata	Magnoliaceae	EN	14.4	30.7	0.486	3
#271	Magnolia tamaulipana	Magnoliaceae	EN	14.06	29.8	0.473	1
#338	Kirengeshoma palmata	Hydrangeaceae	EN	13.06	27.9	0.483	2
#359	Amorphophallus titanum	Araceae	EN	12.74	28.2	0.48	1
#402	Roridula gorgonias	Roridulaceae	thr	12.11	52.8	0.21	1
#435	Amorphophallus palawanensis	Araceae	thr	11.69	29.9	0.405	1
#464	Lanaria lanata	Lanariaceae	thr	11.29	59.4	0.19	3
#499	Geissoloma marginatum	Geissolomataceae	thr	10.9	51.7	0.211	3
#501	Lacandonia schismatica	Triuridaceae	thr	10.89	28.5	0.506	1
#512	Tetramerista glabra	Tetrameristaceae	thr	10.76	46.5	0.24	12
#544	Medusandra richardsiana	Peridiscaceae	thr	10.46	42.8	0.238	5
#548	Scyphostegia borneensis	Salicaceae	thr	10.42	54.2	0.232	8
#590	Eucommia ulmoides	Eucommiaceae	VU	10.09	43.5	0.232	10
#639	Saruma henryi	Aristolochiaceae	EN	9.76	19.8	0.51	1
#722	Amorphophallus gigas	Araceae	thr	9.29	30.5	0.318	1

Source: Forest et al. (2026). EDGE scores for flowering plants. Science. EDGE gymnosperms precursor: Forest et al. (2018), Scientific Reports. FotW analysis by Professor Sven Buerki (Boise State University, Dr. Davidson Endowed Chair of Botany). Hyperlinks lead to live Flora of the World taxon pages.

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