Conservation biology of a rare New England plant: Cynoglossum boreale

Ela Abrams

Cynoglossum boreale Fern. (Boraginaceae), northern wild comfrey, is one of the twenty-one threatened plant taxa identified by the New England Plant Conservation Plan (NEPCoP) for initial regional conservation plans. Cynoglossum boreale is an iteroperous herb that grows primarily in coniferous upland forests with mesic, calcareous soils. There are only five populations in New England, where it used to be found throughout the region. This study establishes baseline demographic data with which to study life history stages and distinguish those most sensitive to environmental factors.

The effects of soil characteristics, competition, and population size on growth and reproductive parameters of C. boreale were investigated at three of the five known New England populations during the summer of 1998. Size classes (small, medium, large, and reproductive) were established based on number of leaves and longest leaf length parameters, and assigned to individual plants. In all three populations, the small size class contained the largest percentage of individuals. Soil characteristics did not explain variation in population status. The removal of competition increased growth in large and reproductive size classes. To examine whether pollinators limit reproduction in small populations, the relationships between population size and seed set, flower production, seeds per flower, and seed weight were examined. Results indicated positive, weakly significant relationships between sub-population size and both seed set and seeds per flower. Flower production and seed weight were independent of population size.

Management suggestions include the use of controlled fires to create new habitat, the removal of co-occurring plant species around large and reproductive plants, hand-pollination to increase cross-pollination and decrease pollinator limitation, and hand-sowing of seeds to increase seedling establishment and population size. Information about population location should additionally be kept confidential in order to protect sites from potential human impact. Research suggestions include investigating potential metapopulation dynamics, seedling establishment in controlled burns, sensitive life history stages, optimal light availability, and outcrossing effects on seed set. A comparison of current, declining New England sites to historical locations and healthy and stable midwestern populations would additionally contribute to a more comprehensive understanding of the conservation biology of this species across its geographical range.