Northern Ireland's Priority Species

Seligeria calcarea – chalk rock-bristle

Seligeria calcarea

Seligeria calcarea (Hedw.) Br.Eur.
Family: Seligeriaceae

A tiny moss that grows on sheltered surfaces of chalk rock. It does not tolerate full exposure to sunlight or heavy shade.

In brief

  • The seven recent Irish records are all from Co. Antrim, including sites at Whitepark Bay, Park Head and Straidkilly Point. There are older records from three other localities in Co. Antrim and one in Co. Londonderry (Benbradagh)
  • It grows only on hard chalk ("limestone") in sheltered, lowland sites that are humid but not heavily shaded. Most records are from stones on north-facing grassland slopes, including places in the vicinity of crags and quarries
  • The best time to see it is in summer when the capsules are mature. It becomes very inconspicuous in the winter
  • It is a priority species because all of the Irish populations are in Northern Ireland and it is rare, with some evidence of decline
  • The main threats are likely to arise from shading by scrub and saplings, but there is no detailed information

Species description
This tiny acrocarpous moss grows on rock as scattered plants or forms diminutive green or olive green turfs, the shoots being up to 2 mm high. The leaves are erect, ovate to ovate-lanceolate or narrowly lanceolate, ending in a rather broad, blunt point composed entirely of nerve tissue. The capsule is ovate to hemispherical, as wide as long, widest at the mouth only when old and empty, with well developed peristome, erect and exserted on a straight seta 1-2 mm long. The spores measure 14-18 μm.

Life cycle
The plants are short-lived perennials arising from a persistent protonema. It is an autoicous species in which capsules are common; gemmae, bulbils and tubers are absent.

Similar species
S. calcarea is distinct from other Seligeria in Ireland in its combination of short, blunt-tipped, entire leaves and peristomate capsules that are not much longer than wide.

How to see this species
S. calcarea can be seen at Whitepark Bay or near Straidkilly Point by very close searching of sheltered chalk rocks.

Current status
Seven records in 1999 resulted from sustained efforts to locate Seligeria spp. during bryophyte surveys in Northern Ireland; almost all of the populations found were small and it was not refound at Benbradagh.

Why is this species a priority in Northern Ireland?
The following Priority Species Criteria apply to S. calcarea:

  • Decline (1% year) with the Irish population restricted (R) to Northern Ireland
  • Irish Red Data Book (RDB) species classed as vulnerable (VU)
  • Red-listed species in Ireland

Threats/Causes of decline
Not known in detail. Most populations of S. calcarea are small and some of them are potentially vulnerable to shading if scrub or saplings become established.

Conservation of this species

Current action

  • Detailed surveys were carried out by NIEA in Co. Antrim and Co. Londonderry in 1999, with supplementary work in later years
  • Some sites for this species are designated as ASSIs by NIEA

Proposed objectives/actions

  • Maintain the number of viable populations of the species
  • Maintain the range of the species
  • Establish appropriate management on appropriate historic sites

What you can do
Careful microscopic study by a skilled bryologist is needed to confirm identification of this species. New sites should be reported to NIEA and the British Bryological Society's Recorder for Mosses (see below).

Further information

British Bryological Society

Atherton, I., Bosanquet, S. & Lawley, M. (eds) (2010). Mosses and liverworts of Britain and Ireland: a

field guide. Wootton, Northampton: British Bryological Society.
Lockhart, N., Hodgetts, N. & Holyoak, D. (2012). Rare and threatened bryophytes of Ireland. NMNI, Belfast.
Smith, A.J.E. (2006). The moss flora of Britain and Ireland. 2nd ed with corrections (paperback). Cambridge: Cambridge University Press.

Text written by:
David Holyoak