Rare Species Guide

  Synonyms

Calamagrostis inexpansa var. brevior, Calamagrostis pickeringii var. lacustris, Calamagrostis stricta ssp. inexpansa

  Basis for Listing

There are only 11 documented and authenticated occurrences of Calamagrostis lacustris in Minnesota. The first is a specimen collected near Fond du Lac in Carlton County in 1889 (the type specimen of the species), the second is a specimen collected at Gunflint Lake in Cook County in 1891, and the third is a specimen collected on an island in Lake Superior in Lake County in 1945. The species was not found again until 2000 when an intensive and highly directed search was made of habitats where it was thought that C. lacustris might occur. This history seems to indicate a rather rare species that may need special consideration in conservation planning. However, the species can be difficult to identify, and its taxonomic status is in question.

The most recent revisionary work that bears upon the species' taxonomy concluded that what we have been calling C. lacustris in Minnesota is actually one of three apomictic (non-sexual) races that are barely distinguishable from each other (Greene 1984). All three races were combined into a single subspecies named C. stricta ssp. inexpansa (A. Gray) C. W. Greene. The sexual race from which the apomictic races were derived was put into a different subspecies named C. stricta ssp. stricta (Greene 1984).

The significance of this taxonomic realignment in relation to the conservation of unique genetic races is not entirely clear. There probably is a distinct and rare entity in Minnesota that corresponds to what had been known as C. lacustris, but the value of protecting it, not to mention the difficulty in identifying it, is problematic. The best course of action may be to retain this species in the special concern category, where it was added in 1996, or drop it from consideration entirely.

  Description

Calamagrostis lacustris is a rather robust perennial grass, with stems 35-90 cm (1.1-3.0 ft.) tall. The stems are usually unbranched and rough to the touch (scabrous), or sometimes smooth. The leaf blades are 11-25 cm (4.3-9.8 in.) long, 1.5-5 mm (0.06-0.20 in.) wide, and flat or involute. The leaf sheaths are smooth or sometimes scabrous, and have a membranous ligule 1-5.5 mm (0.06-0.20 in.) long. The inflorescence is an erect, slender panicle 4-18 cm (1.6-7.1 in.) long, and 1-2 cm (0.4-0.75 in.) wide. Each spikelet consists of a single floret 3-4 mm (1.2-1.6 in.) long; the glumes are usually less than 3 times as long as wide and usually smooth. The callus hairs are abundant and 2-4.5 mm (0.08-0.18 in.) long. The lemmas are 2-4 mm (0.08-0.16 in.) long and have an awn attached to the lower half. The awn is straight or bent, 1.5-2.5 mm (0.06-0.10 in.) long, and projects slightly, if at all, beyond the margins of the glumes (Marr et al. 2007).

  Habitat

From the available information, it appears that C. lacustris occurs on Lake Superior cliffs, northern dry cliffs, northern mesic cliffs, northern bedrock outcrops, northern bedrock shrubland, rocky lakeshores, and other dry, exposed habitats in the northeast corner of the state. In neighboring states and provinces, it has been found on sandy shores, marshy meadows, damp rocks, and gravelly or peaty sites (U.S. Forest Service 1999). Because of the taxonomic difficulties, it cannot be determined with certainty if reports from other states are referring to the same entity that we are studying in Minnesota.

  Biology / Life History

Calamagrostis lacustris has been reported to be apomictic (Greene 1984), meaning that fertile seeds are produced without fertilization. In practical terms, this means the seeds are genetically identical to the parent plant, and, in fact, identical to all other plants in the population.

How an apomictic population fits into a taxonomic classification depends on the particular species concept used by the botanist doing the classifying. Sometimes apomictic populations are considered species, sometimes subspecies, and sometimes given no taxonomic rank at all.

Although the seeds are essentially clones, they behave the same as sexually-derived seeds. They are wind-dispersed, and germinate upon contact with an appropriate substrate. Suitable seedbeds may result from disturbances such as fire, flooding, or ice-scouring. In addition to seeds, C. lacustris has been reported to reproduce by the spread of rhizomes, sometimes forming a colony as large as 15 m x 15 m (50 ft. by 50 ft.) in size (U.S. Forest Service 1999). The species is also reported to need direct sunlight and will disappear if overgrown or shaded-out (U.S. Forest Service 1999).

The best time to search for this species is when the seeds are fully developed between July and August.

  Conservation / Management

There is too little occurrence data for this species in Minnesota to propose meaningful recommendations.

  Conservation Efforts in Minnesota

No known conservation efforts have been undertaken specifically on behalf of C. lacustris.

  References and Additional Information

Greene, C. W. 1984. Sexual and apomictic reproduction in Calamagrostis (Gramineae) from eastern North America. American Journal of Botany 71(3):285-293.

Marr, K. L., R. J. Hedba, and C. W. Green. 2007. Calamagrostis. Pages 706-732 in Flora of North America Editorial Committe, editors. Flora of North America north of Mexico. Volume 24. Oxford University Press, New York, New York.

U.S. Forest Service. 1999. Population viability assessment in forest plan revision. Statement of purpose and reason. Draft species data records: Calamagrostis lacustris. United States Forest Service, Region 9, Milwaukee, Wisconsin. 11 pp.