Northern Ireland's Priority Species

Aulacomnium androgynum – bud-headed groove moss


Distribution map

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Aulacomnium androgynum (Hedw.) Schwaegr.
Family: Aulacomniaceae

Aulacomnium androgynum is a small acrocarpous moss that usually bears a cluster of gemmae on the stem tip. Hence its stems usually look like minute green drumsticks.

In brief

  • There are old records from many parts of Northern Ireland but in the past fifty years it has been recorded only in County Fermanagh, at two localities in Lough Navar Forest

  • In Northern Ireland it grows on peaty humus, often on sandstone rocks; elsewhere, it is often commoner on rotting wood or bark

  • The species is a perennial that can be seen in all months of the year

  • Northern Ireland is its Irish stronghold — it is rare and there is evidence of a large decline

  • Threats to Irish populations of the species are poorly understood, but it is at risk if sandstone crags are shaded by planted conifers

  • A. androgynum has increased in south-eastern England, possibly in response to atmospheric pollution, so its decrease in Northern Ireland is puzzling.

Species description
A. androgynum is a small, erect, acrocarpous moss that grows in tufts or small patches. Individual stems can reach 35mm tall but are usually 10 to 20mm. Most plants have numerous pseudopodia, consisting of rounded clusters of greenish gemmae at the stem tip. The leaves are ovate-lanceolate with the nerve extending to the apex. Capsules are borne on an erect seta and are erect and cylindrical when young, becoming inclined with age.

Life cycle
The sexes occur on separate plants (dioicous). Capsules are very rare, maturing in summer. Reproduction and dispersal almost certainly occur mainly from the gemmae produced at stem apices.

Similar species
A drumstick like pseudopodium occurs in very few other mosses so the plants can often be identified with a hand lens. Otherwise, it is necessary to pay close attention to leaf shape and cell form to be sure of the identification. The most similar species is Aulacomnium palustre (Hedw.) Schwägr. which is usually larger and mostly grows in marshes, but it occasionally occurs as stunted forms in other habitats. A. palustre sometimes produces pseudopodia, when the main distinction is in the presence of two- or three-stratose brownish cells in its leaf base that are lacking in A. androgynum.

How to see this species
In Northern Ireland the species can be found by close searching of peaty ledges on two of the north-facing sandstone scarps (Braade Scarp; Meenameen Scarp) in Lough Navar Forest, County Fermanagh). It can be found all year round. Relevant access permissions should always be sought prior to visiting any sites.

Current status
There are recent records only from Braade Scarp and Meenameen Scarp in County Fermanagh. Some of its old localities have not been resurveyed for bryophytes for many years, so it may well survive elsewhere. The species is common over most of England. Elsewhere it occurs over much of Western and Central Europe, more rarely in Southern and Eastern Europe, and is also known in the Canaries, North Africa, Western and Eastern Asia, North America and Patagonia.

Why is this species a priority in Northern Ireland?

  • A. androgynum is rare and has most of its Irish localities in Northern Ireland, which is therefore its stronghold

  • Evidence of a large decline in Northern Ireland since the early twentieth century.

Threats/Causes of decline
Reasons for the apparent decline of the species over much of Northern Ireland during the past century are obscure, especially since it increased in southern England over the same period. Populations on some of the sandstone scarps in Lough Navar Forest are potentially at risk from shading by planted conifers.

Conservation of this species

Current action

  • Localities in Lough Navar Forest were surveyed for this and other bryophytes by EHS in 1999 and 2000

  • Braade scarp is protected as an ASSI

  • Since the 1999 and 2000 surveys, Forest Service has removed conifers growing close to some of the sandstone scarps

  • Some historic sites elsewhere in Northern Ireland have been resurveyed for bryophytes since 1999.

Proposed objectives/actions

  • Maintain the number of viable populations of this species at the two extant sites in Lough Navar Forest, through appropriate habitat management

  • Resurvey historic sites elsewhere in Northern Ireland

  • If refound, take measures to maintain the populations.

What you can do
This species may be detected by recording mosses in appropriate habitats. Study of mosses is a specialist pursuit since microscopic study is usually needed for reliable identification of species. The Field Studies Council provides courses introducing bryophytes and bryology. The British Bryological Society welcomes beginners to its field trips and indoor meetings.

Further information

British Bryological Society

Field Studies Council

Braade ASSI

Hill, M.O., Preston, C.D. and Smith, A.J.E. (1994). Atlas of the bryophytes of Britain and Ireland. 3. Mosses (Diplolepideae) . Colchester: Harley Books.

Holyoak, D.T. (2003). The distribution of bryophytes in Ireland. Dinas Powys, Vale of Glamorgan: Broadleaf Books.

Porley, R.D. (2001). Mosses and liverworts of the sandstone scarps of the Lough Navar Forest region, County Fermanagh. Irish Naturalists' Journal 26: 393-404.

Smith, A.J.E. (2004). The moss flora of Britain and Ireland. 2nd ed. Cambridge: Cambridge University Press.

Text written by:
David Holyoak