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Recovery Strategy for the Incurved Grizzled Moss (Ptychomitrium incurvum) in Canada (Proposed)


1. Background

1.1 Species Assessment Information from COSEWIC

Date of Assessment: November 2002

Common Name: Incurved Grizzled Moss

Scientific Name: Ptychomitrium incurvum

COSEWIC Status: Extirpated

Reason for Designation: A small moss that is widely distributed in the eastern deciduous forests of eastern North America, and whose frequency of occurrence alternates towards the northern portion of its range. In Canada, the only known location for the species is a single record from a boulder in southern Ontario in 1828. Despite many years of collection made in the region, the species has never been rediscovered.

Canadian Occurrence: Ontario

COSEWIC Status History: Designated Extirpated in November 2002. Assessment based on a new status report.

1.2 Description

Incurved grizzled moss is a small, inconspicuous moss that grows in tufts on rocky substrate. This acrocarpous1 moss typically grows 2–6 mm in height (COSEWIC 2002). The blackish green leaves are curled when dry but erect-spreading and incurved when moist (COSEWIC 2002). The leaves are narrow and concave and are approximately 2 mm in length. The leaf margins are erect and untoothed, with a midrib that runs the length of the leaf (COSEWIC 2002). Capsules are ovoid and smooth. The peristome2 is made up of 16 unpaired, sharply papillose,3 narrow teeth that are fused at their bases (COSEWIC 2002).

Incurved grizzled moss is sometimes confused with similar species, such as Ptychomitrium leibergii, which has longer, broader and bistratose4 leaves and longer setae5 and capsules (COSEWIC 2002).

1.3 Populations and Distribution

Considered “apparently secure” globally (G4), incurved grizzled moss has a temperate global distribution, with populations centered largely in eastern North America. However, the species is also found in some mountainous regions of Europe (COSEWIC 2002). Although incurved grizzled moss is relatively widespread in the eastern portions of the United States, its distribution is more concentrated within the southern states. The former Canadian occurrence was at the northernmost limit of the species' range. Range limits seem to have changed over the past century, shifting south out of New York State (COSEWIC 2002). The status list for rare New York mosses indicates that the species is known to have occurred historically in that state (COSEWIC 2002). In the United States, incurved grizzled moss is currently listed as historical (SH) in New York State and as critically imperilled, imperilled and vulnerable (S1S2 to S3) in Delaware and Tennessee, and it is not ranked in four other states (Georgia, Indiana, Michigan and Virginia) (NatureServe 2006; Appendix 1).

There is only one known record of incurved grizzled moss in Canada (Ireland and Ley 1992; COSEWIC 2002). This occurrence is based on a specimen collected by Drummond in 1828 from a rock near Niagara Falls, Ontario (COSEWIC 2002; Figure 1). There is some uncertainty regarding the precise collection location, and it is therefore not known whether the specimen was actually collected within Canadian borders (COSEWIC 2002). However, a Niagara Falls locality is plausible due to the proximity of historical sites for the species in New York, Ohio, Pennsylvania, Vermont and Michigan (COSEWIC 2002).

This species has not been observed in Canada since the time of the original collection. Owing to the fact that southern Ontario has been relatively well explored, it seems unlikely that the species would have gone unreported for almost 200 years (COSEWIC 2002). A reconnaissance survey conducted in 2001 by J. Doubt, a bryologist with the Canadian Museum of Nature, did not relocate the species (COSEWIC 2002).

There have been reports of the species occurring in Quebec (NatureServe 2006); however, experts have determined that the species in these reports were misidentified (A. Branchaud, pers. comm., 2006).

Incurved grizzled moss has not been assigned a national N rank in Canada and is ranked as SX (extirpated) in Ontario.

Figure 1: Approximate location of Canada's single historic occurrence of incurved grizzled moss (Ptychomitrium incurvum)

Figure 1: Approximate location of </a>Canada's single historic occurrence of incurved grizzled moss

1.4 Needs of incurved grizzled moss

1.4.1 Habitat and biological needs

Incurved grizzled moss tends to inhabit temperate regions of the world (COSEWIC 2002). In Canada, it typically inhabits the deciduous Carolinian Forest Region. It typically grows on the surfaces and in the crevices of boulders of variable chemistry in open hardwood forests. It rarely grows at the base of trees or on logs, and it has also been observed on anthropogenic surfaces, such as rock walls and gravestones (COSEWIC 2002).

Very little is known about the specific biological needs of this species. The moss is autoecious6 and, therefore, is able to self-pollinate (COSEWIC 2002). It is believed to be largely spore-dispersed, as asexual propagules are relatively rare.

Incurved grizzled moss displays considerable adaptability when compared with other bryophyte species (COSEWIC 2002). It has flexibility with respect to the substrates on which it can grow and has two different means of reproduction -- sporophytes and asexual propagules (COSEWIC 2002).

1.4.2 Limiting factors

The major limiting factor for the survival of this species is likely to be climate (COSEWIC 2002). “It seems unlikely that reproductive features limit the species' range to a greater degree than climatic factors” (COSEWIC 2002). There has been an unexplained distributional shift over the past century, which could have led to the extirpation of the species from the northern portions of its range, including New York State (COSEWIC 2002).

1.5 Threats

Threats to incurved grizzled moss are not known for Canada. As the only occurrence has not been relocated since its discovery in 1828, it is impossible to determine the threats that the population faced and what ultimately led to its extirpation.

Human activity could be a threat, as it is with many other rare Carolinian forest plant species; however, incurved grizzled moss remains common in the southeastern United States, within highly populated areas. Acid precipitation and deforestation in southern Ontario also have the potential to affect the survival of this species if it is reintroduced (COSEWIC 2002).

1.6 Actions Already Completed or Under Way

To date, no recovery actions have been taken for this species. A one-day reconnaissance survey was completed in the historical occurrence area in 2001 as part of information gathering for the COSEWIC status report.

1.7 Knowledge Gaps

Little is known about incurved grizzled moss within its North American range, and even less is known about the single historic Canadian record. Research on its biological and ecological needs, habitat requirements and threats to its survival would be required if recovery were to proceed in order to understand the species and its ecological niche in the Niagara Falls area.

As well, research into reintroduction techniques would be necessary for recovery to take place.


1 with gametophyte producing sporophyte at apex of a stem or main branch. Acrocarpous mosses generally grow erect in tufts (rather than mats) and are sparsely or not branched (Missouri Botanical Gardens 2006).

2 A ring of teeth that surround the mouth of the sporophyte capsule (Missouri Botanical Gardens 2006).

3 Bearing papillae; a papilla is a cell ornamentation or solid microscopic protuberance (Missouri Botanical Gardens 2006).

4 Composed of two cell layers (Missouri Botanical Gardens 2006).

5 Elongated portion of the sporophyte between the capsule and foot (the stalk) (Missouri Botanical Gardens 2006).

6 Completes all life stages on a single host (Raven et al. 1992).