Euphrasia hudsoniana var. ramosior Sell & Yeo
Hudson Bay Eyebright
Basis for Listing
Euphrasia hudsoniana var. ramosior is an arctic-alpine plant persisting in Minnesota as a relic from the arctic climate that was present in the state immediately following the last glacial ice retreat ~10,000 year ago. In Minnesota, it only occurs in habitats closely associated with the shores and islands of Lake Superior. One of the earliest collections was made in 1878 by J. H. Sandberg in Lake County from the rocky shores of the lake. For the next 100 years, only a dozen or so populations were documented in the state. Since 1978, approximately 50 additional occurrences have been reported as a result of intensive survey efforts. It would be misleading to assume this equates to a population increase, especially when one compares the ecological integrity of Lake Superior's shorelines today with that of even 150 years ago, and is more likely a product of increased search efforts.
Euphrasia hudsoniana var. ramosior is a small annual with stems erect, simple, or branching, up to 35 cm (13.8 in.) long. It has small, white to pale blue flowers with contrasting bluish purple guidelines. The base of the lower lip is colored with a bright yellow spot. The floral leaves are moderately hirsute (hairy), 6-8 mm (0.24-0.31 in.) long, with 4-6 teeth per side. The petals are small, just 5-6.5 mm (0.20-0.26 in.) long. The calyx, bracts, and leaves are pubescent. The cauline leaves are opposite, 4-11 mm (0.16-0.43 in.) long, and strongly wedge shaped at their base. They have a terminal lobe and 1-5 acute to blunt teeth per side. Similar and often quite confusing look-a-like species include E. stricta (drug eyebright) and E. nemorosa (common eyebright). Technical characters including pubescence, and leaf and teeth shape are necessary in order to determine species. These characters can be quite variable and sometimes end in uncertain results.
In Minnesota, E. hudsoniana var. ramosior occurs only in close proximity to the shores of Lake Superior, in habitats shaped and climatically influenced by the dynamics of the lake. Habitats include bedrock shores, cliffs, and cliff tops. Plants may grow in crevices, on ledges, and at the edges of small pools. Soil is often sparse and substrates range from cracks in the bedrock, to shallow gravels, to wet, cobbly sand, to mossy mats and thin peats. Lake Superior provides cool conditions and natural disturbance regimes that maintain the immature soils and non-forested conditions seemingly well suited for E. hudsoniana var. ramosior .
Biology / Life History
Species in the genus Euphrasia are known to be insect pollinated but observations of insect visits are reported to be infrequent (Sell 1970). It is likely that small flowered Euphrasia species, such as E. hudsoniana var. ramosior, reproduce primarily by self-pollination. They are also known to be hemiparasitic on a wide variety of host plants. Although plants can flower and fruit without establishing this parasitic relationship, they show greater vigor when in association with a host plant. Euphrasia species, especially those growing in close proximity to each other, are known to hybridize and E. hudsoniana var. ramosior hybrids are known to exist in North America (G. Gusarova, University of Oslo, pers. comm.). Nothing more specific is known about pollination, parasitic relationships, or hybridization of E. hudsoniana var. ramosior in our region.
Conservation / Management
The genus Euphrasia is taxonomically difficult. Different authors often recognize different species concepts and determining which species even occur in a region remains troublesome. In addition to E. hudsoniana var. ramosior, it is likely E. stricta and possibly E. nemorosa also occur in Minnesota. A new treatment for Euphrasia is currently being prepared for the Flora of North America, which should result in a better understanding of the species' taxonomy and distribution. Minnesota plant records will then need to be further reviewed in order to determine/verify which species occur here.
Conservation Efforts in Minnesota
Approximately one third of the known occurrences of E. hudsoniana var. ramosior occur on state-owned lands. Most of these are within State Park jurisdictions while two are located in Scientific and Natural Areas. Many of the remaining occurrences are in private ownership.
References and Additional Information
Given, D. R., and J. H. Soper. 1981. The arctic-alpine element of the vascular flora at Lake Superior. National Museums of Canada, Publications in Botany No. 10, Ottawa, Ontario. 70 pp.
Sell, P. D., and P. F. Yeo. 1970. A revision of North American species of Euphrasia L. (Scrophulariaceae). Botanical Journal of the Linnean Society 63:189-234.
Voss, E. G. 1996. Michigan Flora. Part III: Dicots (Pyrolaceae-Compositae). Cranbrook Institute of Science Bulletin 61 and University of Michigan Herbarium, Ann Arbor, Michigan. 622 pp.