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Watershield - Brasenia schreberi
State Rank Reason (see State Rank above)
Brasenia shreberi is rare in Montana, where it is known from over 12 waterbodies in the northwestern portion of the state. The state population apears to be at least 3,000 plants though many occurrences are poorly documented or have old data. Population trends are generally unknown, though declines at Blanchard, Seeley, and possibly other lakes are suspected because of threats from the competitive and invasive Nyphaea odorata, shoreline development, and recreational use (boating). These are on-going threats where monitoring is needed to quantify reported threats to inform management.
Continued revisits to known occurrences, at specified intervals, to collect data on population parameters, habitat conditions, and potential threats are necessary to maintain an accurate and timely state conservation status rank. Monitoring at a subset of occurrences is necessary to track population trends and assign a timely and accurate state conservation status rank.
Continued revisits to known occurrences, at specified intervals, to collect data on population parameters, habitat conditions, and potential threats are necessary to maintain an accurate and timely state conservation status rank. Monitoring at a subset of occurrences is necessary to track population trends.
General Description
Watershield is a rhizomatous perennial aquatic herb with branches which rise through the water, floating leafblades (lily pads), and emergent flowers. The leaves have long petioles attached alternately to the branches and centrally to the undersides of the floating leaf blades. The broadly elliptic to oval leaf blades are 4-12 cm long and 3-8 cm wide. Solitary flowers are held just above the water on long peduncles. The flowers usually have 3 sepals and 3 petals which are similar, translucent reddish-purple colored, linear to lance-shaped, and 1-1.5 cm long. There are 4-14 pistils and 12-36 purplish stamens which are about the same length as the petals and sepals. The leathery, beaked fruits are 6-8 mm long and mature underwater.
Phenology
Flowering in August.
Diagnostic Characteristics
Distinguished from other water lilies (Nuphar and Nymphea) by its relatively small, purplish, many pistilled flowers and by its relatively small, truly peltate (with petiole attached to the center of the blade) leaves.
Species Range
Montana Range
Range Descriptions
Native
Range Comments
Most of North America, widespread in other parts of the world except Europe. Sparse.
Observations in Montana Natural Heritage Program Database
Number of Observations: 104
(Click on the following maps and charts to see full sized version)
Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Habitat
Shallow water of lakes, sloughs, and slow-moving rivers in the valley zone.
Ecological Communities Associated with this Species
Stewardship Responsibility
Threats or Limiting Factors
Reported threats to Montana’s populations of Watershield include motorboat recreation where it occurs at some lakes, competition from the invasive American Water-lily (Nymphaea odorata), and shoreline development. Information that quantifies the impacts of these reported threats is greatly needed.
Climate change could also pose a potential risk to the state's populations. The MTNHP conducted a species-level assessment using the Climate Change Vulnerability Index (CCVI) in 2021, which resulted in a Less Vulnerable rating to climate change. However, field-based data on the timing and magnitude of impacts from climate change are not available.
References
- Literature Cited AboveLegend:
View Online Publication
MTNHP Threat Assessment. 2021. State Threat Score Assignment and Assessment of Reported Threats from 2006 to 2021 for State-listed Vascular Plants. Botany Program, Montana Natural Heritage Program, Helena, Montana.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?- Frodge, J. D., Thomas, G. L. and G. B. Pauley. 1990. Effects of canopy formation by floating and submergent aquatic macrophytes on the water quality of two shallow Pacific Northwest lakes. Aquatic Botany 38:231-248.
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
- Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
- Raymond, M., and P. Dansereau. 1953. The geographical distribution of the bipolar Nymphaeaceae, Nymphaea tetragona, and Brasenia schreberi. Memoires du Jardin Botanique de Montreal 41: 1-10.
- Web Search Engines for Articles on "Watershield"
