Alkaline wing-nerved moss (Pterygoneurum kozlovii) assessment and status report: chapter 5
COSEWIC Status Report
Alkaline Wing-nerved Moss
The Pottiaceae is a large and diverse family of mosses with many of its species restricted to seasonally dry environments. It is a taxonomically difficult family and has been undergoing extensive review in recent times (Zander 1993). The genus Pterygoneurum is comprised of a group of relatively small, soil-inhabiting species that are characterized by wing-like flaps or lamellae on the upper side of their leaf costae (mid-ribs). There are three other species of Pterygoneurum in North America (Anderson et al. 1990): P. lamellatum (Lindb.) Jur., P. ovatum (Hedw.) Dix., and P. subsessile (Brid.) Jur., and they are all found in Canada (Ireland et al. 1987). Both P. ovatum and P. subsessile are relatively common throughout the driest portions of the interior of British Columbia. Pterygoneurum lamellatum, however, is rare, and has been found only twice in the province: adjacent to White Lake, south of Penticton, and at a recently discovered site in the northwest Cariboo Region (this site was discovered in 2002 while searching for P. kozlovii). In addition, P. kozlovii and P. lamellatum are restricted to seasonally wet and alkaline habitats, whereas the other two species are characteristically found only in much drier sites.
Pterygoneurum kozlovii differs from P. lamellatum, P. ovatum, and P. subsessile principally in that its capsules (spore sacs) are both hidden in the leaves at maturity (immersed) and lacking an operculum (a lid on the spore sac which allows for spore release; this condition is referred to as cleistocarpous). Of the other species, only P. subsessile has immersed capsules, but they are operculate, and its calyptra (a vegetative cap that covers part of the top of the mature spore sac) is mitrate (shaped like a bishop's cap) in contrast to the calyptra of P. kozlovii, which is cucullate (hood-like, with a split on one side). Also, the mature capsules of P. subsessile are usually exposed at maturity, whereas the capsules of P. kozlovii are usually somewhat hidden by rather tightly wrapped leaves.
Because of some distinct gametophytic (haploid, vegetative generation) and sporophytic (diploid, spore producing generation) differences between Pterygoneurum kozlovii and other members of the genus Pterygoneurum, as well as distinct differences between North American plants and those in Europe, this species may warrant a change in taxonomy, at both the species and genus level (McIntosh 1986).
The following description has been derived principally from McIntosh (1986, 1989) and McIntosh and Paige (2001). These descriptions were based on Vanek (1952; as Pterygoneurum smardaeanum Vanek) and Abramova et al. (1973). More details are provided here than is normal for status reports since much of this information is not yet readily available in North American literature.
Pterygoneurum kozlovii is a short, 2-3 mm tall, acrocarpous (producing female structures and sporophytes at the tips of the main stems) moss that usually grows in small (less than 1 cm2) to medium sized (2-4 cm2) patches, sometimes forming rather widespread, yet intermittent turfs. Mature plants have a bulbous appearance, as a result of the presence of sporophytes, whereas younger plants are relatively narrow. Most plants are characterized by twisted leaves (Figure 1 is a photograph of a cluster of plants with maturing sporophytes). Small bulbils, or vegetative propagules, are often present along the underground stems and these may develop into plants.
Mostly on left side of photograph (~X10).
The leaves of Pterygoneurum kozlovii are light green to yellow-green, and are about 1 mm long, ovate-lanceolate to ovate, concave, and taper rather abruptly towards the awn (Figure 2). Leaf margins are plain to weakly recurved and usually weakly toothed near the apex. The leaf costa is pale brown and has two large central or guide cells. The upper surface of the costa above mid-leaf is comprised of two to four cells that form a base to the characteristic flaps. These lamellae are usually two, rarely three and they average four to six cells in height. Their margins are usually irregular and their terminal cells papillose. The costa is usually long-excurrent, especially on the upper leaves, as a clear, smooth to weakly toothed awn, or hair-tip, giving larger colonies a somewhat hoary appearance.
The middle and upper leaf cells are rhombic or oblong, to irregularly quadrate or rectangular, and mostly range in size from 10-20 µm wide by 15-35 µm long. These cells are usually smooth, although occasionally weakly, and rarely strongly, papillose (having small bumps on the cells' surface). In larger, mature leaves, the cells at the leaf apex towards the base of the awn are distinctly longer and somewhat narrower than those below. The basal leaf cells are rectangular to long-rectangular and larger than the upper cells. Also, they are clear and thin-walled, and appear weakly inflated in some leaves.
Pterygoneurum kozlovii is autoecious, with both male and female structures present on each plant. The leaves around the sporophyte usually number 3-4, and resemble the adjacent leaves, except they are usually longer (up to 1.5 mm long). They become paler and die as the sporophyte matures and often form a cover around the mature capsule. Sporophytes are common (Figure 1). Ovate to round, 0.8-1.0 mm capsules mature through the late autumn into the spring, when they often give fertile plants a golden-brown colour. Capsules lack a regular opening for spore release, although an apparently non-functional differentiated band of small cells is present near the top of the capsule in this species. A tiny apiculus is present at the top of the capsule. Spores are large, from 30-45 µm in size, and are weakly ovate to spherical, and roughly papillose. Spores are released as the capsule decomposes. The calyptrae cover much of the top half of the capsule.
Additional keys can be found in McIntosh (1986) and Savicz-Ljubitzkaja and Smirnova (1970, in Russian). Additional illustrations are found in Vanek (1952) and McIntosh (1989).
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