A botanist from the University of Bradford has discovered a rare plant fruiting for the first time in more than 130 years.

Dr Alistair Headley, with a colleague from London's Natural History Museum, found the endangered Nowell's limestone moss reproducing in the Yorkshire Dales.

And he has unlocked the secret of why the plant almost faced extinction, giving fresh hope for the future recovery of the species.

Dr Headley made the exciting find while on a mission to document the last remaining patches of the moss, which is called zygodon gracilis in Latin, with experts from the Natural History Museum.

Of 500 patches they measured and recorded in the Dales, in a survey funded by English Nature, they found just one small area fruiting.

"Locating the moss was very exciting, but even more so when we realised why it hadn't been able to reproduce successfully all these years," said Dr Headley. "The moss patches, which are either male or female and mate via the spreading of spores, just haven't been close enough to each other."

Until this discovery, Nowell's limestone moss was thought to exist only on two old sections of dry-stone in the Yorkshire Dales and had joined the endangered species list.

It was last seen reproducing in 1866 by well-known amateur botanist John Nowell who discovered and named the moss.

Dr Fred Rumsey, a plant diversity researcher at the Natural History Museum in London, said it was an important breakthrough. "This discovery gives us a great opportunity to slow down and possibly even halt the extinction of a very interesting but mostly overlooked species. It's also gratifying to know that sometimes simple observation can be just as effective as high-powered science."

The plants John Nowell found in 1866 are in the Natural History Museum's collections and can be viewed by appointment.