Synonyms

Gentianella amarella ssp. acuta

  Basis for Listing

Gentianella amarella is known to occur throughout northern temperate and arctic regions of Europe, Asia, and North America. The most recent revision of this genus (Gillett 1957) concluded that the European population consists of a single subspecies (ssp. amarella), but the North American population consists of five separate subspecies. The most widespread and variable subspecies in North America is subspecies acuta, which is the only subspecies that occurs in Minnesota.

Within Minnesota, G. amarella ssp. acuta is limited to remnant prairie habitats in the northwest corner of the state. Many of these habitat fragments have been searched by botanists in the course of rare plant surveys. The number of sites that have already been searched and which appear to have good habitat for the species is in the low hundreds, yet G. amarella ssp. acuta was found to occur in only six of them. The greatest number of plants counted in any one site is about 20. It is unlikely that more than a handful of habitats remain to be searched, and it is also unlikely that repeat visits to sites that have already been searched will discover many additional plants.Because the species is an annual, plants may be present only when conditions are favorable for germination and maturation, otherwise persisting in the seed bank, which can make survey efforts challenging.

One of the sites with a known population of G. amarella ssp. acuta has been a considered for a sanitary landfill, and plants in another population were perilously close to an underground fiber optic cable that was put through its habitat. Other documented threats include cattle grazing and invasion by non-native species. Given its rarity and threats to the few remaining populations, Gentianella amarella ssp. acuta was listed as a special concern species in Minnesota in 1984.

  Description

Gentianella amarella ssp. acuta grows to a maximum height of 70 cm (2.3 ft.), although 20-40 cm (0.7-1.3 ft.) may be more typical for Minnesota plants. The stem is simple or branched. The basal leaves are elliptic with a blunt or rounded tip, and a base that gradually tapers to the stem or to a slender petiole. The basal leaves are up to 4 cm (1.6 in.) long and 1 cm (0.4 in.) wide. The leaves on the middle portion of the stem are elliptic, ovate, or ovate-lanceolate in shape with an acute tip and sessile attachment. They have a rounded or cordate base and are up to 6 cm (2.4 in.) long and 2 cm (0.75 in.) wide. The upper leaves are similar to the middle leaves but progressively smaller and more acute.

The flowers occur in clusters at the top of the stem and in the axils of the leaves. The calyx of the flower is green, up to 2.5 cm (0.98 in.) long, with 4 or 5 lobes. The corolla is tubular with 5 variously shaped lobes that are about half the length of the tube. It is white to blue and up to 2.5 cm (0.98 in.) long. The fruit is a dry capsule about as long as the corolla, whichproduces many small seeds (Gillett 1957).

  Habitat

Habitats in Minnesota can be classified as mesic prairie or wet prairie on loamy soil. Within this somewhat broad habitat type, G. amarella ssp. acuta may be localized in or near shallow depressions where the soil is moister and perhaps more alkaline. These are generally high quality remnant habitats that have not been invaded by non-native species to any great extent, and have not been subjected to intensive cattle grazing.

  Biology / Life History

Gentianella amarella ssp. acuta has been reported as being an annual in North America, meaning it completes a generation in 12 months or less (Gillett 1957). However, at least one study conducted in England concluded that plants of the closely related Gentianella amarella ssp. amarella are biennial (Kelly 1985). In biennials, the seeds germinate in the spring then grow through the summer and fall. The plant then becomes dormant in the winter without having produced flowers. The plant begins growth again the second spring and will flower late in the second summer. The plant will then die before the start of the third year, so each generation takes 24 months (Kelly 1985).

Any seeds that are produced lie dormant in the soil over the winter. Most seeds will germinate the following spring, although some will remain dormant for an unknown number of years. Eventually a bank of dormant, yet viable, seeds will develop in the soil (Kelly 1985).

One study in Finland (Huhta et al. 2003) showed that individual G. amarella ssp. amarella plants can tolerate the effects of light grazing. The study concluded that when less than 10% of the stem is removed there was no pronounced effect on the plant's performance; biomass was fully compensated and fruit production may have actually been increased. If 50% of the stem is removed, the plants are able to compensate in terms of biomass, but not in terms of fruit production. How this might pertain to the grazing of domestic livestock on Minnesota populations of G. amarella ssp. acuta, and the habitat in which it occurs, is unknown. However, it is important to remember that G. amarella ssp. acuta is an annual or perhaps a monocarpic biennial, meaning an individual plant has only one chance to produce flowers and fruits before it dies.

The best time to search for G. amarella ssp. acuta is during the flowering season, which typically extends from early August through the middle of September.

  Conservation / Management

As is the case with most rare plant species that occur in remnant prairie habitats, the conservation of G. amarella ssp. acuta depends on maintaining and protecting the physical, hydrologic, and biological integrity of its habitat. Cattle grazing can greatly hamper reproduction in this species as would mowing anytime after about the middle of July. Both these activities, if too intense or done at the wrong time, will remove flowers or developing fruit before the seeds have a chance to mature. Since G. amarella ssp. acuta is an annual or biennial, the loss of a seed crop for even one year could have significantly harmful effects on a small population. However, because some disturbance may be important in creating conditions for germination and maturation, grazing or haying may be useful in maintaining populations. The seasonal timing of either is critical, and the frequency, intensity, and duration of grazing are all important. Haying should be delayed until plants have matured seed, and grazing after this point should also be relatively safe, especially if the seeds of consumed plants remain viable after passing through an animal. Research is needed to determine what the limits for other variables should be, although it is almost a certainty that repeated season-long heavy grazing is incompatible with the survival of this species. Until more is known, grazing should be light and of short duration, and the response of G. amarella ssp. acuta should be carefully monitored.

Several programs and resources are available to land managers and landowners to help protect and manage remaining prairie parcels including the Native Prairie Bank Program, the Native Prairie Tax Exemption Program, and a prairie restoration handbook.

  Conservation Efforts in Minnesota

Two populations of G. amarella ssp. acuta, one last seen in 1982 the other in 1990, occur in state Wildlife Management Areas managed by the Minnesota Department of Natural Resources. While this may impart some level of protection, the current status of these populations is unknown and no known conservation efforts have been undertaken to specifically manage for the species within these areas.

  References and Additional Information

Gillett, J. M. 1957. A revision of the North American species of Gentianella Moench. Annals of the Missouri Botanical Garden 44(3):195-269.

Huta, A.-P., K. Hellstrom, P. Rautio, and J. Tuomi. 2003. Grazing tolerance of Gentianella amarella and other monocarpic herbs: why is tolerance highest at low damage levels? Plant Ecology 166(1):49-61.

Kelly, D. 1985. On strict and facultative biennials. Oecologia 67:292-294.