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Nowell's limestone moss

Taxonomic information

Common Name: Nowell’s Limestone Moss

Latin Name: Zygodon gracilis

Family: Orthotrichaceae

Nowell’s Limestone Moss.
Photograph by Robert Goodison.

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Description

Nowell’s limestone moss is a very rare species that is only known from four areas in Britain which are all within the Craven Limestone area of the Yorkshire Dales National Park. Although originally found growing on scree slopes, the few surviving populations are found on a stretches of drystone wall in the Pen-y-ghent area of the National Park. This species continues to be on the UK list of priority species for biodiversity action.

This species is named after John Nowell, a local bryologist who first discovered the moss in 1860. Nowell’s limestone moss is a dioicous moss, meaning that there are separate male and female plants. The moss can sexually reproduce where climatic conditions are right and male and female plants are within 20 cm of each other. In addition the moss can reproduce vegetatively, where new plants are propagated from vegetative tissues only. However, this method of reproduction means that the moss will never colonise any new sites. One of the main reasons for the rarity of Nowell’s limestone moss is that the male and female plants were thought to be too far apart from each other to sexually reproduce. This is highlighted by the fact that until relatively recently, the last person to find the moss in capsule, or fruiting, was John Nowell in 1866.

In 2003 surveyors from the University of Bradford and Natural History Museum in London undertook detailed survey work to accurately plot the location of all populations of this moss at its historical sites on the slopes of Pen-y-ghent. Just over 500 clumps of Nowell’s limestone moss were recorded and approximately 70% of the plants found were female. The surveyors were delighted to find one fruiting body. This was the first time that this species had been witnessed ‘in capsule’ for nearly 140 years.

Now that the distribution of the species has been accurately mapped, any dry stone walling work in this area can be undertaken sympathetically to ensure that the survival of this endemic species is not put at risk.