Unmasked: the botanical Kiwi who hitched to Britain

A tiny botanical gem that made its home over just four sites along the southern reaches of Britain has finally found its true roots on the other side of the world. One of the country’s most perplexing rare plants, Murphy’s threadwort (Telaranea murphyae) challenged scientists for decades by requiring monitoring as an alien species that was only known to grow in England. But now scientists at the Royal Botanic Garden Edinburgh (RBGE), working as part of an international group of taxonomists, have employed the latest technology to reveal it as a stowaway from New Zealand: putting an interesting new conservation onus on the Kiwi government.

Found only at Tresco and St Mary’s on the Isles of Scilly; Branksome Chine, Poole in Dorset and Alum Chine, Bournemouth, the tiny Murphy’s threadwort was recognised a distinct species in 1965 because of its unique characteristics. However, these physical attributes also caused it to be regarded as a non-native of unknown origin. As a result, it created its own set of contradictions because, despite being rare, as long as the species was not recognised as native, it could not be considered a priority in the UK Biodiversity Action Plan. So, it could not be the subject of conservation measures. At the same time, the UK had to take sole responsibility for its preservation until a country of origin could be found.

“There was always a fair amount of certainty that this was not a native plant”, explained Dr Laura Forrest of  RBGE. “The Victorian craze for ferns had seen many gardens import living tree ferns from countries such as Australia and New Zealand and many smaller plants made their way to the UK by hitching a ride on the trunks of these sought-after specimens. As the hosts became established, some of their little passengers escaped into the local landscape and were able to survive. If they became a threat to native species, conservationists would focus on how to eradicate them. Otherwise, they were considered of little consequence. Suspicions were strong that Murphy’s threadwort was one such case. But, no specimens could be found anywhere else to prove the point.”

However, the coloniser was eventually exposed when the collaborative team of scientists from RBGE, Germany and the US were able to utilise new technology which means plant identification no longer relies on the human senses alone.

“Through the extraction of DNA material from  Murphy’s threadwort we were able to  compare it to other threadworts from around the world and, for the first time, we were able to demonstrate that the plant growing in the UK is actually another species: Long’s threadwort (Telaranea tetradactyla), which is already known from its native habitat in New Zealand” added Forrest. “Now, it will receive a change of name and the UK will no longer have any legal obligation to conserve this alien plant. The onus for its protection, if any is required, now falls on the New Zealand government”.

The Royal Botanic Garden Edinburgh is a charity (registration number SC007983)