The tree is cross between a rowan and a whitebeam

Two specimens of the newly-named Catacol whitebeam (Sorbus pseudomeincichii) were discovered by researchers on the Isle of Arran.

The tree is cross between the native rowan and whitebeam.

The discovery followed work by Scottish Natural Heritage (SNH), Dougarie Estate and Edinburgh Royal Botanic Gardens.

Graeme Walker, of SNH, said recent research into the genetics of whitebeam trees had shown that the population was much more diverse than previously thought.

"These are unique trees which are native to Arran and not found anywhere else in the world," he said.

"We knew about the Arran whitebeam and the cut-leaved Arran whitebeam, which are also crosses between rowan and different species of whitebeam, but it has been really exciting to discover a completely new species.

"It is very complex picture but we think that the Arran whitebeams are gradually evolving towards a new type of tree which will probably look very similar to a rowan."

A team from the Royal Botanic Gardens has been collecting seeds and cuttings to ensure the long-term survival of the trees.

Work is also underway to protect the two specimens on Arran.