Malaxis monophyllos var. brachypoda (Gray) F. Morris & Eames
White Adder's Mouth
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Basis for Listing
Malaxis monophyllos var. brachypoda is one of several hard to find small, bog orchids that inhabit conifer swamps in northern Minnesota. It is not the rarest one, that distinction probably belongs to M. paludosa (bog adder's mouth), but it certainly is not the most common one. Some indication of its rarity can be inferred from the results of field searches conducted by highly trained botanists. As of 2008, more than 50 occurrences of M. monophyllos var. brachypoda had been documented in Minnesota with the vast majority of them recorded since 1990. The greater number of recent records reflects an increased awareness of this species among field botanists, and a desire by concerned orchid conservationists to discover more sites. The number of potential habitats that were searched without success is not known for sure, but they far outnumber the sites where the species was found. Even in sites where M. monophyllos var. brachypoda has been found, the number of individuals is usually low, often fewer than 10. Rarity alone, however, is not the only cause for concern. The sensitive and fragile nature of this species' habitat is probably of greater concern. Malaxis monophyllos var. brachypoda was listed as a special concern species in Minnesota in 1996.
The stems of M. monophyllos var. brachypoda are 11-22 cm (4.3-8.7 in.) tall, and they arise from a globular pseudobulb. There is 1 leaf and it is attached above the base of the stem; the petiole of the leaf sheaths the stem. The blade of the leaf is ovate-elliptical in shape, 2.7-8 cm (1.1-3.1 in.) long, and 1.3-3.7 cm (0.5-1.5 in.) wide. The inflorescence is a slender, terminal raceme, 4-11.5 cm (1.6-4.5 in.) long, with 14-34 minute greenish flowers; each flower is subtended by a lanceolate bract 1-2 mm (1.04-0.08 in.) long. The sepals are ovate-lanceolate to oblong-lanceolate and 1.7-2.5 mm (0.07-0.10 in.) long. The petals are linear to linear-lanceolate, reflexed, and 1.5-2 mm (0.06-0.08 in.) long. The floral lip is somewhat triangular in shape, 1.4-2 mm (0.06-0.08 in.) long, and 1-1.7 mm (0.04-0.07 in.) wide at the base. It is contracted near the middle to produce a narrow lanceolate tip, and the base of the lip is dilated to produce lobes that curve forward.
In Minnesota, M. monophyllos var. brachypoda is found in conifer swamps within forested rich peatlands, typically under a canopy of Thuja occidentalis (northern white cedar), Picea mariana (black spruce), Abies balsamea (balsam fir), Fraxinus nigra (black ash) and Larix laricina (tamarack). These forests are usually at the margins of stream or river channels, lake basins, or large peatlands, or at the bases of beach ridges. Within the forest, often many or all of the plants in a population occur near the upland margin of the swamp. Soils range from shallow or deep peat to organic sediments. Surface water pH is weakly acidic although close to neutral (>6.0). Soils are saturated and the water table is at the surface except on higher hummocks and moss that mound over coarse woody debris (Minnesota Department of Natural Resources 2003). Water-filled hollows are often present and appear to be the micro-site where M. monophyllos var. brachypoda is most often found.
Biology / Life History
Life history documentation for M. monophyllos var. brachypoda is sketchy, but a few basic attributes can be inferred from the structure of the plant. Individual plants are capable of regenerating themselves from the annual production of pseudobulbs, but this does not allow the creation of additional individuals. Therefore, actual reproduction is accomplished only by seeds, which are produced annually under favorable conditions. Pollination takes place in mid summer and is probably achieved with the aid of small flies or fungus gnats. The seeds are very small and capable of being carried great distances on air currents. However, the seed capsules are held only a few inches above the ground and the dense forest probably dampens wind velocities, so it seems unlikely that seeds are often carried very far. Populations appear rather stable over time; at least there are records that seem to confirm the persistence of M. monophyllos var. brachypoda at a particular site for 60+ years.
Conservation / Management
There is little that can be done at the micro scale to manage populations of M. monophyllos var. brachypoda. A more effective strategy may be to concentrate on maintaining the ecological integrity of the entire forest environment of this species. This would preclude direct alteration to the tree canopy and disturbance of the ground layer of vegetation, particularly the sensitive moss community. Also, any project that might alter the natural hydrology of the system must be examined closely. This would include road building activity, ditching, culvert replacement, and pipeline construction.
Conservation Efforts in Minnesota
Although no specific conservation efforts have been undertaken on behalf of M. monophyllos var. brachypoda, a few of the populations are located within State Parks and Scientific and Natural Areas, which may impart some level of protection.
References and Additional Information
Catling, P. M., and L. K. Magrath. 2002. Malaxis. Pages 627-532 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 26. Oxford University Press, New York, New York.
Minnesota Department of Natural Resources. 2003. Field guide to the native plant communities of Minnesota: the Laurentian mixed forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 352 pp.
Smith, W. R. 1993. Orchids of Minnesota. University of Minnesota Press, Minneapolis, Minnesota. 172 pp.