CPC National Collection Plant Profile

Rorippa subumbellata

Photographer:
Gail Durham

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CPC National Collection Plant Profile

Rorippa subumbellata


Family: 
Brassicaceae  
Common Names: 
marsh cress, Tahoe yellow-cress
Author: 
Rollins
Growth Habit: 
Forb/herb
CPC Number: 
3773

Distribution
Protection
Conservation
References


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Rorippa subumbellataenlarge
Photographer: Gail Durham
Image Owner: USFS LTBMU

Rorippa subumbellataenlarge
Photographer: Gail Durham
Image Owner: USFS LTBMU


Rorippa subumbellata is Not Sponsored
Primary custodian for this plant in the CPC National Collection of Endangered Plants is: 
Edward Guerrant, Ph.D. contributed to this Plant Profile.

 
Rorippa subumbellata


Lake Tahoe is a popular vacation destination for many Americans. Perhaps, too popular. This hot-spot for boaters and sunbathers is the only naturally occurring site of the Lake Tahoe yellowcress. Rorippa subumbellata inhabits a seven-foot "tidal" zone between the low and high water lines of Lake Tahoe. This low-growing perennial has proven to be adaptable from year to year depending on the amount of rainfall. During years with low rainfall, the cress can grow lower on the exposed beach from seed or rootstock. In years of higher rainfall, the cress is limited by the availability of exposed beach. This delicate lakefront habitat is threatened by constant abuse from boat wake, dock construction, and uncontrolled recreation. Due to continuous abuse of the unique Lake Tahoe yellowcress habitat, only an estimated 14 of the 48 historically known populations survive.

Efforts are being made to limit construction and the degradation of the yellowcress' habitat. This mustard family member has been listed as "Endangered" by the state of California since 1982 and "Critically Endangered" by the state of Nevada since 1980. On December 11th 2000, the League to Save Lake Tahoe and the Center for Biological Diversity submitted a formal petition to the U.S. Fish & Wildlife Service to list the Tahoe yellow cress as an Endangered species. Without federal protection and the efforts of local conservationists and Tahoe area residents, the plant will continue to slide toward extinction.

Distribution & Occurrence

State Range
  California
Nevada
State Range of  Rorippa subumbellata
Habitat
  Coarse sand and sandy soil of beaches, dunes, stream inlets, and backshore depressions along the shore of Lake Tahoe, high in the Sierra Nevada Mountains, almost exclusively between the elevations of 6223 ft and 6230 ft.

Distribution
  NV: Carson City, Douglas County, Washoe County
CA: n SNH- northern High Sierra Nevada (Lake Tahoe Basin) (El Dorado and Placer Co.)

Beaches surrounding Lake Tahoe

Number Left
  There are approximately 42 different sites around the lake where Rorippa subumbellata has been found at some point since surveys began in 1979. Many may have been extirpated, and populations seem to come and go depending on the conditions (California State Lands Commission 1998). In 1999, 14 sites were observed: 5 on private property, 9 on federal land. The number and size of populations fluctuates with changing lake levels (USFWS 2000).

Protection

Global Rank:  
G1
 
5/22/2006
Guide to Global Ranks
Federal Status:  
C
 
10/25/1999
Guide to Federal Status
Recovery Plan:  
No
 

State/Area Protection
  State/Area Rank Status Date  
  California S1.1 E 4/1/1982  
  Nevada S1S2 CE 3/30/2001  

Conservation, Ecology & Research

Ecological Relationships
  Fluctuating water levels both help and hinder this species. This plant thrives in years when the water level is lower and there is less competition from plants that require moisture. (CA Dept. of Parks and Recreation 1991). The lower water level also creates more available habitat. In years with high lake levels, the habitat becomes unavailable for colonization and prolonged exposure water may kill individuals. However, occasional high water levels may benefit Tahoe yellowcress by removing other plant species eventually opening up new habitat. Before damming, water levels fluctuated on a yearly cycle. Levels were highest in the fall and winter and lower in the spring and summer. Now, because of stream damming, levels remain fairly constant. High water is maintained in the spring and summer months, which is the growing season of Rorippa subumbellata (NFGEL 2000).
Seed and plant material may be dispersed by wind and wave action, leading to colonization of new sites (NFGEL 2000).
Associated species include: Carex douglasii, Phacelia hastata var hastata, Juncus balticus, Salix spp., Lepidium virginicum var. pubescens, various grasses. (Reynolds 1988).
Little is known about the reproductive biology of this species. The method of pollination is not known (NFGEL 2000).

Threats
  Habitat destruction (beach houses, boat ramps, recreation, etc) (Reynolds 1988).
Soil/sand disturbance (CA Dept. of Parks and Recreation 1991).
Rising lake levels (Reynolds 1988).
Grazing (Ferreira 1986).

Current Research Summary
  Determination of genetic diversity through isozyme analysis. Samples from 11 populations around the lake were analyzed to determine the genetic diversity within and between sites. The results show extremely limited variation. Eight of the eleven populations were identical for the 23 loci examined (all homozygous). The remaining three populations were nearly identical. They were nearly homozygous except for one or two loci, which were variable. The results indicate very low levels of gene flow and suggest that most plants around the lake may be a single clone (NFGEL 2000)
Germination trials at The Berry Botanic Garden yielded no germination of apparently good seed. Seeds were either cold stratified or not, and then subjected to either constant 68F (20C) or alternating 50F/68F (10C/20C) temperatures. Further research is needed to determine optimum germination requirements (BBG File). If no success is achieved, seed viability tests should be conducted.
Ongoing biological studies by the Tahoe-Baikal Institute. Student interns have studied human disturbances, monitored populations, and observed the pollinators of Rorippa subumbellata.

Current Management Summary
  Sites managed by the US Forest Service and California State Parks are monitored regularly and are fenced to reduce or eliminate recreational disturbances (USFWS 2000).
Three sites on U.S. Forest Service land were planted with 500 seedlings each in 1988. Populations were surveyed in 1990 and again in 1993. There was an overall survival rate of 12 to 43% (California State Lands Commission 1998).
In 1999, the Tahoe-Baikal Institute directed a study to monitor all populations of the Tahoe Yellowcress. They designed a protocol that could be followed to monitor the plant from year to year. They also recommended future management strategies that may contribute to the conservation of the Tahoe yellowcress in the basin.
A draft Conservation Strategy is being written and should be finalized and distributed in the spring of 2002 (Gross, pers. comm.)
Seeds from three sites are stored at The Berry Botanic Garden.

Research Management Needs
  Fence populations (Ferreira 1986).
Investigate possible mycorrhizal associations and other vegetation relationships.
Maintain and protect populations, especially the three largest, which contain different alleles than the smaller populations (NFGEL 2000).
Determine how long dormant plants can survive inundation by lake water.
Determine the dominant method of site colonization. Is it by seed, re-sprouting roots, or deposition of plant material (i.e. fragments)? Determine success of reproduction.
Study the longevity and viability of seeds.
Study pollination and reproductive biology. Determine patterns of gene flow.
If worse comes to worst, manipulate lake levels in order to create more suitable habitat and promote establishment.
Study the biological and ecological reasons for this species' rarity, including: population structure and dynamics, life history, and environmental requirements (California State Lands Commission 1998).

Ex Situ Needs
  Determine germination requirements.
Determine if seeds can effectively be stored for long periods of time.
Collect and store seeds from populations around the lake, especially from populations that contain unique genes.
Determine effective propagation and re-introduction methods.

References

Books (Single Authors)

Abrams, L.; Ferris, R.S. 1944. Illustrated Flora of the Pacific States: Washington, Oregon, and California. Stanford, CA: Stanford University Press.

Mozingo, H.N.; Williams, M. 1980. The threatened and endangered plants of Nevada. Portland, OR: U.S. Fish & Wildlife Service and Bureau of Land Management. 268p.

Munz, P.A.; Keck, D.D. 1959. A California flora. Berkeley, CA: Univ. California Press. 1681p.

Books (Edited Volumes)

James C. Hickman, Editor. 1993 The Jepson manual: Higher plants of California. Berkeley: University of California Press. 1400p.

Electronic Sources

CDFG. (2001). Special Vascular Plants, Bryophytes, and Lichens List. Biannual Publication, Mimeo. 141 pp. California Department of Fish and Game, Natural Diversity Database. Accessed: 2001.

CNDDB. (2000). Calfornia Natural Diversity Data Base (CNDDB). Version 2.1.2. California Natural Diversity Database. Accessed: California Department of Fish and Game, Sacramento.

NNHP. (2001). Detailed Rare Plant and Lichen Lists. Nevada Natural Heritage Program. http://www.state.nv.us/nvnhp/selists.htm. Accessed: 2002.

Journal Articles

1941. (Original Publication). Contributions from the Dudley Herbarium. 3, 5: 177-178.

USFWS. 1996. Notice of Reclassification of 96 Candidate Taxa. Federal Register. 61, 40: 7457-7463.

Personal Communications

Gross, B. Letter to BBG staff from Beth Gross, California Tahoe Conservancy. Dated October 3, 2001. On file at BBG.

Reports

1991. 1991 monitoring report on Rorippa subumbellata. California Department of Parks and Recreation. Unpublished report.

1998. Tahoe Yellow Cress Draft Biological Assessment. California State Lands Commission. Administrative Draft.

Ferreira, J.E. 1986. Natural Diversity Database Field Report. Submitted to the Natural Diversity Database, California Department of Fish and Game.

NFGEL. 2000. Evaluation of Genetic Diversity in Tahoe Yellow Cress (Rorippa subumbellata). Annual Report 1999-2000 (FY00). Placerville, CA: National Forest Genetic Electrophoresis Laboratory.

NNHP. 2001. Nevada Rare Plant Atlas: Index to Maps and Fact Sheets. Portland, Oregon and Reno, Nevada: Carson City: Nevada Natural Heritage Program, compiled for the U.S. Department of the Interior, Fish and Wildlife Service. Grant EP-3-12.

Reynolds, J. 1988. Monitoring plan for Rorippa subumbellata. Unpublished paper. Eldorado National Forest.

USFWS. 2002. Candidate and Listing Priority Assignment Form. U.S. Fish and Wildlife Service. p.11.

Theses

Ferreira, J.E. 1987. The population status and phenological characteristics of Rorippa subumbellata (Roll.) at Lake Tahoe, California and Nevada. [M.A. Thesis]: California State University. Sacramento, California.


  This profile was updated on 3/4/2010
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