Spoon-leaved moss (Bryoandersonia illecebra) COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements

Crum and Anderson (1981) indicate that Bryoandersonia illecebra prefers soil substrates, particularly on banks, but that it sometimes occurs on rocks or tree bases. Known Canadian collections of B. illecebra were all found on soil, but at least superficially represent a range of habitat types and moisture levels: cedar swamp, deciduous woodlot, pine plantation, and Crataegus-Juniperus virginiana scrub. However, all confirmed extant populations of B. illecebragrow in or at the border of flat, low-lying areas (Figures 6 & figure 77) affected seasonally by standing water. In all three cases, the species grew close to populations of Helodium paludosum, an infrequent, temperate species reaching, in the northern part of its range, southern Ontario and Quebec. H. paludosum is associated with swamps, marshes, and wet meadows. It is not known whether wet communities provide growing conditions that are ecologically important for B. illecebra in the northern part of its range, or if swampy sites are merely less often disturbed by human activity.

The global distribution of Bryoandersonia illecebra (Figure 3) approximates that of the eastern deciduous (Carolinian) forest of North America (as described by, e.g. Argus & Pryer 1990), and as such its habitat in Canada is restricted to the warm southern tip of Ontario (Maycock 1963). Many rare Canadian vascular (e.g. Lamb & Rhynard 1994, Oldham 1990) and non-vascular (Crum 1966) plant species are restricted in the same way, reaching their northern distribution limits in this same region. It is not clear whether the northern distribution limit of B. illecebra responds directly to climatic factors, as is suspected of many eastern deciduous forest plants (Delcourt & Delcourt 2000), or if the suitable habitat is provided by the forest itself.

Table 2. List of specimens of B. illecebra known for Canadaprior to this report. Information was gathered from herbarium labels, herbarium records, and communication with collectors. Records were sought at the Museum of Nature (CANM), the Missouri Botanical Garden (MO), the New York Botanical Garden (NY), the Royal Ontario Museum (TRTC), Lakehead University (LKHD) as well as several southern Ontario Universities (of which only the University of Western Ontario ([UWO]) possessed collections). Records were also reqested from the Royal Botanic Garden in Edinburgh (E), where the herbarium and notes of William Stewart, a prolific southern Ontario collector, were sent upon his death in 1997. All CANM and UWO specimens were verified by the author. “Sex” refers to whether the collections seen were determined to represent male (M) or female (F) plants, or could not be determined (U). Because sex determination in bryophytes can be destructive to samples, the information below should be considered preliminary. No collections seen included sporophytes. Two seasons of field work (2001, 2002) were devoted to visiting the locations of contemporary collections. An ‘s’ under the column for a given year indicates that the location was searched. An ‘f’ indicates that populations were found at the site.
Specimen location Locality, habitat Abundance Sex Collector (Coll. #),
date, identified by:
Ownership, protection Field work 2001 Field work 2002
CANM Essex County,

Uknown
U
M.J. Oldham (B-92)
March 28, 1982
ID: R.R. Ireland
Private
Cedar Creek ANSI
s
f
CANM
E
Middlesex County, Unknown
U
F.S. Cook (776)
April 15, 1973
(as Cirriphyllum illecebrum)
ID: F.S. Cook
Vidi: R.R. Ireland
Private
None
s
 
CANM
E
UWO
Elgin County, Few
U
W.G. Stewart (1266)
April 15, 1973
ID: R.R. Ireland, H.A. Crum
Private
None
s
s
E
UWO
Elgin County, Few
F
W.G. Stewart (1529)
April 27, 1975
ID: W.G. Stewart, Vidi: F.S. Cook
Private
None
 
s
E Elgin County Few
U
W.G. Stewart (1710)
May 17, 1980
ID: W.G. Stewart
Private
None
 
s
UWO Elgin County Abundant
F
W.G. Stewart (1923)
April 1, 1983
ID: W.G. Stewart
Crown
Mackay Forest
Elgin Hiking Trail
 
f?
E Elgin County Abundant
U
W.G. Stewart (1923)
April 1, 1983
ID: W.G. Stewart
Private
None
 
s
CANM
MO
NY
Upper Canada Unknown
(but probably abundant)
U
T. Drummond
(192) – exiccata
1925-1927
(as Hypnum illecebrum)
Unknown
Unknown
   
NY Canada. Rocky Mts. Unknown
U
A.R. Wallace Unknown
Unknown
   
Table 3. List of specimens of B. illecebra representing known extant populations found in connection with this report. Specimens are housed at the Universityof Alberta Devonian Botanic Garden (DBG) and were identified by the author.
Locality,
habitat
Abundance Sex Collector (Coll. #),
date
Ownership,
protection
Previously known?
Essex County 2 colonies:
10 cm x 5 cm
(100% cover)
1.5 m x 1 m
(65% cover)
F
J. Doubt
(9319, 9330)
August 15, 2002
Private
Cedar Creek ANSI
Yes
(see Table 2)
Elgin County 1 colony:
4 m x 3 m
(90% cover)
F
J. Doubt
(9349)
August 17, 2002
Crown
Mackay Forest
Elgin Hiking Trail
Possibly (see ‘Canadian Range’ section of this report; also Table 2)
Welland County, 1 colony:
20 cm x 10 cm
F
J. Doubt
(9430)
August 21, 2002
Niagara Peninsula Conservation Authority
Willoughby Marsh Conservation Area
No

Figure 6. Habitats in Essex and Elgin Counties supporting healthy extant populations of Bryoandersonia illecebra.

  1. Acer community in Cedar Creek ANSI, Essex County.
  2. B. illecebra in the Cedar Creek Acer community occupied to tops of small clay hummocks.
  3. Mixed deciduous habitat near Paynes Mills, Elgin County.
  4. Near Paynes Mills, B. illecebra formed a continuous mat several metres in diameter and crept up tree bases.
Figure 6. Habitats in Essex and ElginCountiessupporting healthy extant populations of Bryoandersonia illecebra

Figure 7. Habitat in Welland County supporting extant population of Bryoandersonia illecebra.

  1. Acer swamp community in Willoughby Marsh Conservation Area near Fort Erie, Ontario.
  2. In Willoughby Marsh, B. illecebra grows on a tree-base root, above the level of the apparent usual water level.
Figure 7. Habitat in WellandCountysupporting extant population of Bryoandersonia illecebra

Trends

Bryoandersonia illecebra is at the northern edge of its global range in Canada. Bryophyte (and other) species at range limits may occupy very isolated, atypical pockets of habitat where certain conditions coincide to approximate those characteristic of regions where the species is more common (e.g. Brown 1984, Hedderson 1992). Thus, habitat factors required by B. illecebra in southern Ontario may not be obvious and may be quite rare.

The character of most sites in which Bryoandersonia illecebra was recorded previously differed somewhat, in 2002, from that encountered by past collectors (to the extent that this was possible to determine). Nearby natural areas, though scarce, generally supported what is thought to be appropriate habitat. Unfortunately several previously known locales were described only by lot and concession numbers, which can encompass 200 acres of land, making it difficult not only to search for the populations but also to assess whether or not the population’s habitat has changed since it was last seen.

Evidence of human activity at two of the lot/concession addresses visited in 2001 was obvious (e.g. agricultural activity and recreational vehicle traffic in Middlesex, mechanical forest thinning in Elgin). Human activity was also associated with these habitats (or, at least, those in the immediate vicinity) twenty or more years ago when the original collections were made. The degree to which this activity influenced the moss populations, positively or negatively, is unknown.

Intensive urban, agricultural, and industrial development characterize southern Ontario, and resultant habitat fragmentation and destruction are often cited as threats to Carolinian habitats and flora in Canada (Argus & Pryer 1990, Klinkenberg et al. 1990, Lamb & Rhynard 1994, Maycock 1963, Oldham 1990). This problem is especially acute for species associated with forests, and most Ontario collections of Bryoandersonia illecebrawere made at treed sites. Allen et al. (1990) report that the Carolinian life zone occupies the most urbanized and agriculturalized area of the country, supporting one quarter of Canada’s population. Habitat destruction and alteration is implicated in for most range contractions observed in European bryophytes (Söderström 1992). It should be noted, however, that the G5-ranked B. illecebra remains secure in the southern part of its distribution, despite the dramatic impacts (Delcourt & Delcourt 2000) of human activity on deciduous forest habitat throughout eastern North America.

Air quality in south-west Ontario is generally poorer than in the rest of the province (Ontario Ministry of the Environment 1996). The sensitivity of bryophytes to air pollution is well-documented, and pleurocarpous mosses (such as Bryoandersonia illecebra) may be affected more than acrocarpous ones (Rao 1982, Lepp & Salmon 1999). This kind of factor may lead to the loss of B. illecebra populations in sites where the conditions conducive to growth appear to be met.

Figure 8. Habitats in Essex and Elgin Counties that have changed substantially since the last documented collection ofBryoandersonia illecebra.

  1. Crataegus-Juniperus virginiana community (2002) in the Cedar Creek ANSI (Essex County, Ontario) described in 1982 by M.J. Oldham upon first discovery of B. illecebra at this site. A small amount (a few stems) of B. illecebra was found in this community, but much more was present in an adjacent Acer community (Figure 5).
  2. Deciduous woodlot near West Lorne, Elgin County, Ontario, where William Stewart collected B. illecebra in 1973. This site was identified only by lot and concession number, and many plant community types are found at this address. No B. illecebra was found here despite visits in 2001 and 2002.
Figure 8. Habitats in Essex and ElginCountiesthat have changed substantially since the last documented collection of Bryoandersonia illecebra

Figure 9. Habitats in Elgin County that have changed substantially since the last documented collection ofBryoandersonia illecebra.

  1. Hillside near St. Thomas, Elgin County, Ontario, where William Stewart collected B. illecebra in 1983. No B. illecebrawas found here in 2002.
  2. Creek through ‘Jolleys Swamp’ near St. Thomas, Elgin County, Ontario, where William Stewart collected B. illecebra. No B. illecebra was found here in 2002.
Figure 9. Habitats in ElginCountythat have changed substantially since the last documented collection of Bryoandersonia illecebra

Because Bryoandersonia illecebra is at its northern range limit in Canada, Canadian populations may also be especially vulnerable to seemingly even minor enviromental change. While one may intuitively expect a warming trend to favour the growth and establishment in Canada of species with ranges centred further south, concomitant changes in the moisture regime may have the opposite effect, particularly in view of the apparent affinity of extant populations for lowland habitats.

Protection/ownership

Two of the three extant populations of Bryoandersonia illecebra found in 2002 are on public land. One site, in Elgin County, falls within the McKay Forest managed by the Ontario Ministry of Natural Resources. The only land use currently permitted in the McKay forest is hiking along the Elgin Hiking Trail, and the introduction of higher impact land uses is not anticipated (Ron Gould, personal communication). Populations of B. illecebra will be taken into account during the development of a recently initiated management plan for the McKay Forest.

The other publicly owned site, in Welland County, is part of Willoughby Marsh, which is managed by the Niagara Peninsula Conservation Authority (NPCA). Willoughby Marsh is large (592 ha) and is a site designated for the conservation of other rare species (Brady 1980). However, the only population of Bryoandersonia illecebra known to exist there borders a road, and can therefore not be protected to the same extent as most of the marsh. The NPCA has been made aware of the location of B. illecebra on its land and has indicated its eagerness to protect the plants (Kim Frolich, personal communication).

The third site of an extant population is privately owned, but is part of an Ontario Area of Natural and Scientific Interest (ANSI), providing it some protection through stewardship and municipal zoning. The Cedar Creek ANSI is described by Eagles and Beechey (1985) as the most significant natural site in Essex County not under public ownership, due to its large size, its potential for beneficial research and education, and its high aesthetic and historical value. It encompasses diverse and significant land forms, communities, habitats, and species (Eagles and Beechey 1985). The national and provincial importance of the Cedar Creek ANSI is widely acknowledged among local and provincial authorities, who take close interest in activities at the site, although the hawthorn scrub community and areas of clay-based soil are reputedly of relatively lower interest with respect to Carolinian species. According to the local branch of the Ontario Ministry of Natural Resources (D. Jacobs, personal communication), a stewardship agreement was reached with the owner of the parcel supporting known Bryoandersonia illecebra populations in the mid-1980s, but the land management has shifted since that time. The land is zoned as “estate residential”. The lack of a tree-cutting by-law in Essex County has apparently made conserving some parts of the ANSI difficult (D. Jacobs, personal communication), although this problem has not arisen in connection with the B. illecebra site.

The status of Bryoandersonia illecebra at sites where no extant populations were found is unknown. Concerted search efforts (Table 1) failed to re-discover the species, although in several cases the sites were too large to survey in entirety, and small populations may yet persist. All of these sites are privately owned. One such site borders a popular hiking trail, which may help to protect the site from certain kinds of land use. The remaining sites are not protected. One of these (Jolley’s Swamp in Elgin County) was listed as a biologically significant area by Klinkenberg et al. (1990), but conversations with the owners and people who have visited the site indicate that the quality of the site may have diminished since the designation was made.

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