Texas wild rice is an aquatic herbaceous perennial which can be found growing only in the cool, clear waters of the San Marcos River in Texas. This species was so abundant in the 1930's that the local irrigation company considered it difficult to keep this plant from clogging its ditches. In striking contrast, this species is now listed as federally endangered (USFWS 1978), with only a few populations known in the wild. A main cause of this decline is the fact that water has been pumped out of the Edwards Aquifer to supply water for agriculture, industry, and human use. This directly effects the spring flow of the San Marcos River, which this wild rice depends upon. Lowering of the river water levels is a major threat to the survival of this species.
Texas wild rice is related to commercially grown wild-rice, and therefore a potentially invaluable resource of hardy genetic stock.
This aquatic grass is found in the San Marcos River, forming large clones or masses of clones firmly rooted in shallow gravel beds near the middle of the river. This plant is adapted to and requires fast-flowing, high quality water at a constant year-round temperature. Critical habitat was designated in 1980. (WWF 1990; USFWS 1980)
Upper San Marcos River in Hays County, Texas
• 140 clumps in one unprotected population
• 100 plants introduced at Spring Lake, 90 surviving and doing well, starting inflorescence development
• population maintained on the Southwest Texas State University campus in an outdoor cement raceway
Current distribution of wild rice extends from the uppermost part of the San Marcos River just below Spring Lake dam and throughout the critical habitat down to an area slightly below the wastewater treatment plant, except for the river portion between the Rio Vista railroad bridge and the dam above Cheatham Street.
• Groundwater pumping of Edwards aquifer
• Pollution from vegetation management
• Stream modification by damming
• Recreation--including swimming and boating in and around the populations
• Nutria (aquatic rodents) eating stalks
Current Research Summary
Research has been conducted by the Department of Biology, Southwest Texas State University and The San Marcos National Fish Hatchery and Technology Center. Dr. Mike Antolin of Colorado State University in Fort Collins, Colorado has been doing studies on the genetics of the wild and captive populations at SWT and SMNFH&TC. Christina Walters and Darren Touchell at NSSL are working on cryopreservation techniques of Texas wild rice. (CPC Annual Report, 1998)
Current Management Summary
In 1998, Paula Powers reported that she was working in a collaborative restoration project with Dr. Robert Doyle, North Texas State University, Denton. This project involves identifying potential restoration sites and establishing methods for transplanting Texas wild rice into the San Marcos River.
Research Management Needs
• Response to disturbance
• Seed dispersal and seedling recruitment
• Genetic analysis
• Public education campaign
• Restore/maintain the historic flow of the San Marcos River
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