Spoon-leaved moss (Bryoandersonia illecebra) COSEWIC assessment and status report: chapter 7

• Previous page
• Table of contents
• Next page

Population Sizes and Trends

Extant populations are not extensive. Their sizes are detailed in Table 3. Careful examination and re-examination of most previously known sites for Bryoandersonia illecebra, with, in some cases, detailed directions to the populations, did not result in the discovery of extant populations. These populations are assumed to have decreased in size or to have disappeared, although past collectors of Bryoandersonia illecebra in Canada did not record population size in detail. William Stewart made brief reference to population sizes in Elgin County: at two locations there were “few”, while at the Paynes Mills / Edwards Farm site the species was “abundant”. Drummond’s collection documents an evidently large population (based on the fact that it included material enough to make an exsiccata), but the precise locality in Canada is not known.

Evidence suggests that Bryoandersonia illecebra is very rare in Canada. Few extant populations were encountered in connection with this report, despite surveys of previously recorded localities and other promising southern Ontario natural areas. Southern Ontario has enjoyed prolific botanical and, specifically bryological exploration (Figure 4), decreasing the probability that many unknown populations exist. The species’ large size and distinctive appearance make it conspicuous in the field, and it is unlikely to have been overlooked by botanists.

The G5 rank given to the eastern North American endemic Bryoandersonia illecebra (Ontario Natural Heritage Information Centre 2001) shows that the species is evidently secure in North America. The species’ rarity in Canada contrasts with its abundance in the United States. Very few states have published bryophyte status lists, making it difficult to determine precisely where the species becomes rare. The Missouri Botanical Garden (2001) and the New York Botanical Garden list few sites in New York and Pennsylvania, and none in Ohio or Michigan, which may indicate that the species is less frequent in the states bordering Canada. However, Nancy Slack (personal communication) writes that B. illecebra is present and abundant in some parts of New York, and B. illecebra does not appear on the New York status list for rare mosses (Clemants & Ketchledge 1993).

Successful natural migration north from the United States seems unlikely given the apparent climatic limitation of Bryoandersonia illecebra and other Carolinian species and given the destruction and fragmentation of Carolinian habitats. The effects of global warming may alter the situation by changing the distribution of favourable habitats. Introduction of the species to favourable sites, or the introduction of male plants to extant female populations may prove fruitful if it were determined that such an attempt was warranted.