Conservationists are in a race against time to prevent one of the world’s rarest island plants from disappearing forever.
Seeds collected from the only surviving wild dendroseris neriifolia tree, which was found clinging to a cliffside in Chile, arrived at the Millennium Seed Bank at Kew Wakehurst near Haywards Heath last month.
Endemic to Chile’s remote Juan Fernández Islands, the critically endangered tree daisy has been reduced to a single known wild individual after decades of habitat loss, invasive species and failed recovery efforts.
Scientists are turning to ex-situ conservation by beginning emergency germination trials that may represent the species’ last realistic chance of survival, with the hope of growing plants to maturity and securing seeds for long-term conservation.
X-ray analysis on the newly arrived seeds at Kew’s MSB has revealed that 25 of the 29 seeds sent to Kew are potentially viable.
To maximise the chances of long-term survival, the seeds have been carefully divided between conservation and propagation efforts. Eight seedlings are now establishing, of which three will soon be sent to LBG, Royal Botanic Garden Edinburgh.
How did the plant become so rare?
Once concentrated in ravines and low-lying areas on Robinson Crusoe Island, D. neriifolia declined dramatically; by 1980, only eight surviving wild individuals remained.
As the population continued to decline, the species was identified as a high conservation priority during the 1990s, prompting intensified recovery efforts by CONAF Park Rangers. Despite reintroduction efforts in the early 2000s, the breakdown of protective measures in 2017 allowed invasive species to enter the site, leaving just one tree in the wild today, and an ex-situ collection established at the National Botanical Garden of Chile failed due to climatic conditions.
There is, however, currently one young specimen growing in VerdeNativo botanic gardens in Chile.
Recovery has been further complicated as 90 per cent of seeds are non-viable owing to geographical isolation, while individuals in gardens suffer from hybridisation meaning their seed cannot be used.
The Juan Fernández Islands, located 760 km off Chile’s coast, are a global biodiversity hotspot, with an estimated 1.7 endemic species per km². Around 65 per cent of their plant species are found nowhere else on Earth, and the archipelago supports 97 per cent of Chile’s endemic fish species and 45 per cent of its endemic bird species.
What is a dendroseris neriifolia tree?
The entire genus of dendroseris (known as ‘cabbage’ trees) is exclusively found on the Juan Fernández Islands, and they are the only plants in the world known to feature unusual, rare ‘tree-daisy’ forms with daisy-like flowers atop a woody, branching trunk. The pressures these plants face include widespread forest clearance and intensive grazing by introduced mammals. Invasive plants also suppress endemic vegetation, while repeated fires have further destabilised already vulnerable habitats.
One endemic species that relies on dendroseris flowers is the critically endangered Juan Fernández firecrown hummingbird. Without these plants, there would be catastrophic effects on vital plant-pollinator interactions and the fragile ecosystem in which it exists.
How were the seeds collected?
Collecting the seeds is no easy task due to the tree’s extreme location. Clinging to the side of a steep cliff on Robinson Crusoe Island, the tree is supported with ropes to prevent it from falling. Working in precarious conditions, collectors carefully climbed along the length of the trunk to reach the flowering branches, where mature seeds are captured in nets.
Seed collection takes place each March, when the one-seeded fruits are fully mature and ready for harvest. This year, a total of 400 seeds were collected.
Felipe Sáez, a plant biotechnology engineer and administrator of PNAJF, said: “The successful transfer of these seeds represents one of the most significant collaborative efforts to safeguard the flora of Juan Fernández and is the result of an international partnership led by Jardín Botánico VerdeNativo, together with the National Forest Corporation (CONAF) through Parque Nacional Archipiélago Juan Fernández (PNAJF). In addition to D. neriifolia, the teams have also facilitated the transfer of seeds from two additional dendroseris species from Robinson Crusoe Island: D. litoralis and D. pruinata. Both species will undergo germination and propagation trials at Logan Botanic Garden and Kew Wakehurst.”
Seeds at Kew
At Kew, eight seeds are being used in germination and cultivation trials to better understand the conditions needed for seedling survival and to grow plants to maturity for future seed production. Eight seedlings are now starting to germinate, and once old enough three plants will be shared with Logan Botanic Garden through the critically endangered species pipeline project. The remaining seeds will be placed into long-term conservation storage at the MSB, providing a vital safeguard against the species being lost forever in the wild or during cultivation efforts.
RBG Kew’s seed processing manager Sarah Gattiker and botanical horticulturalist Alice Livingstone said: “Following X-ray analysis and germination tests, together with the invaluable horticultural advice from Felipe Sáez Quintana and Gonzalo Rojas Sea, CONAF, we made the decision to direct sow the seeds into compost in the glasshouses at Wakehurst. This reduced the risk of the seedlings being exposed to too high humidity on the laboratory agar plates and minimised seedling disturbance, therefore hopefully leading to the highest potential seedling development for this species. Through this collaborative effort all eight seedlings have now germinated.”
Race against time
Diego Penneckamp, scientist at Jardín Botánico VerdeNativo, author of the Flora Vascular Silvestre del Archipiélago Juan Fernández (2018), said: “It is a race against time. This international collaboration to support the last remaining individual could prevent the extinction of a species that represents a unique lineage with its own natural history.”
Seed collectors from CONAF aim to send another seed collection to the UK next year to strengthen the programme further.
