Oxytropis campestris var. johannensis
|Johann's locoweed, late yellow locoweed, St. John river oxytrope, St. John's oxytrope|
|Elizabeth J. Farnsworth|
The following Participating Institutions are custodians for this species in the CPC National Collection:
New England Wild Flower Society
The conservation of Oxytropis campestris var. johannensis is fully sponsored.
Elizabeth J. Farnsworth contributed to this Plant Profile.
Oxytropis campestris var. johannensis is a river-side legume endemic to Maine and eastern Canada. Its deep taproot and compact architecture help it withstand the frequent flooding and ice scour common along wild, rocky northern rivers, and its populations shift along the shoreline when disturbance occurs. Although relatively secure in southern Ontario, the species has declined in extent from 118 km to 28 km of shoreline in its former Maine stronghold along the St. John River (which gave it its common name). Its taxonomic relatedness to the similar but disjunct taxon, Oxytropis campestris var. chartacea (Fassett) Barneby of Wisconsin (U.S. Fish and Wildlife Service 2001, Wisconsin State Herbarium 2001) still need to be resolved; these could constitute the same taxon, meaning the variety is more widespread than previously thought. In any case, populations are threatened by changes in hydrology and sedimentation brought on by damming and riverbed mining and upland clearing, as well as encroachment of invasive species.
Research and Management Summary:
Apart from preliminary taxonomic treatments, no published research could be located on this taxon. However, the New England Wild Flower Society has performed germination trials on it and published a Conservation and Research Plan in 2001.
Oxytropis campestris var. johannensis is a perennial herb growing 4-55 cm tall with short-stems that emanate from a tap-rooted base. Its pinnately-compound leaves consist of 7-45 hairy leaflets each 5-25 mm long. In July, its flowers form at the end of a leafless stem, clustered into a raceme of up to 14 blooms. The 12-18 mm-long flowers are purple or rarely white, with the typical "butterfly" shape of the Papilionoid group. The plant produces sparsely hairy legumes (pods) that are 1.5-2.5 cm long.
Distribution & Occurrence
Oxytropis campestris var. johannensis is primarily found along gravelly and rocky shores of rivers, on cobbles, beaches, rock outcrops, ledges, and cliffs (Gleason and Cronquist 1991, Haines 2001). In New England, the taxon appears to prefer circumneutral rock types (Haines 2001). The shores where the taxon occurs are subject to seasonal heavy ice scour during snowmelt, and this type of disturbance keeps the area open and conducive to colonization by this plant and others, like the Furbish lousewort (Pedicularis furbishiae), that are poor competitors with other plants in more stable habitats. Along the St. John River in Maine and New Brunswick, the plant occurs at elevations between 160 and 190 m.
The relatively pristine St. John River, coursing through calcareous glacial tills and bedrock, hosts a uniquely diverse array of rare and specialized plant species in the region, and possesses extremely high conservation significance (Haines 2001). The species is also reported from the mixed-woods plains ecotone of southern Ontario, along the intertidal freshwater zone of the lower St. Lawrence River estuary (Catling and Cayouette 2001).
According to Haines (2001), associated plants include: dwarf sand cherry (Prunus pumila var. depressa); tufted hairgrass (Deschampsia caespitosa); alpine milk-vetch (Astragalus alpinus var. brunetianus); Lake Huron tansy (Tanacetum bipinnatum ssp. huronense); cut-leaved anemone (Anemone multifida); chives (Allium schoenoprasum); northern meadow groundsel (Senecio pauperculus); and alpine sweetbroom (Hedysarum alpinum var. americanum).
|Maine harbors six extant populations along the St. John River, down from 14 historically known populations (Haines 2001). Most populations have not been censused recently or have only incomplete counts; current estimates are in the order of magnitude of 1000 plants in Maine (Haines 2001). Populations are more numerous in Ontario, Quebec, and New Brunswick (Catling and Coyouette 2001, NatureServe 2001), but exact numbers are unavailable. Population localities and numbers are likely to vary greatly from year to year due to frequent river disturbance.|
Conservation, Ecology & Research
The taxon flowers from June to July in Maine, and fruits develop and mature in July (Haines 2001). In one population studied by Haines (2001), about 50% of the plants flowered in each of two years. Insect pollinators would be expected for the papilionaceous flowers, and bees may be attracted to the purple color, but this has yet to be studied. Seeds are likely to be dispersed by river water.
Seed germination is likely sensitive to water level (enhanced when water levels drop in spring) and by rising summer temperatures following snowmelt, if Oxytropis campestris var. johannensis behaves like var. chartacea (Wisconsin Department of Natural Resources 2001) or like a related riparian species, Oxytropis riparia (Delaney 1986).
Herbivory rates have not been reported for this taxon. However, the plant may produce secondary compounds (principally flavinoid glycosides) that are toxic to potential herbivores, much as other members of the "locoweed" genus do (Sun 1991).
Finally, it is unknown whether Oxytropis campestris var. johannensis harbors nitrogen-fixing rhizobial root symbionts. Nodulation has been documented for several other Oxytropis species (Laguerre 1997), so it might be expected in this taxon, particularly given its affinity for calcareous habitats.
Dams that diminish flood magnitudes and otherwise change river hydrology
Gravel mining on river shores (particularly in New Brunswick)
Trampling by vehicles using river shore as a roadbed
Invasive plant species
The New England Wild Flower Society (Framingham, Massachusetts) has conducted seed germination trials for Oxytropis campestris var. johannensis (Brumback 1989). Fifty seeds collected in early August, 1986 yielded three seedlings within three weeks of sowing. Six additional seedlings also germinated following a three-month treatment in moist cold storage. However, dry, cool storage appeared to promote the best germination. Seed held for 9 years in seed bank conditions remained viable.
The North American Rock Garden Society also appears to possess seed of Oxytropis campestris var. johannensis.
Current and potential impacts of invasive species on the taxon must be critically assessed.
Taxonomic relatedness of Oxytropis campestris var. johannensis to Oxytropis campestris var. chartacea and other members of the O. campestris complex should be determined to evaluate the conservation status of both taxa.
Isely, D. 1998. Native and Naturalized Leguminosae (Fabaceae) of the United States (exclusive of Alaska and Hawaii). Salt Lake City, Utah: Monte L. Bean Life Science Museum, Brigham Young University.