Texas wildrice (Zizania texana Hitchc.), an endangered macrophyte, is endemic to the San Marcos River and Spring Lake in Hays County, TX. Its population declined dramatically between 1940 and 1967. In a reintroduction program that was initiated by the Southwest Texas State University in 1992, plants were transplanted into five microhabitats at a density of 10 plants/m2. Seasonal monitoring identified an initial increase in plant size followed by high mortality in three of five sites. Data suggests that stem density is a good indicator of future transplant success and that current velocity is an important environmental factor associated with transplant success. However, herbivores have continually clipped reproductive culmns below the water surface. This limits transplants to clonal reproduction.
Christina Walters and Darren Touchell at NSSL are working on cryopreservation techniques of Texas wild rice. (CPC Annual Report, 1998)
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.
Endemic to the upper few km of the San Marcos River in south-central Texas, where it was locally abundant as recently as the the 1950s. It is now reduced to a precariously small population covering about 1200 square meters on an urbanized segment of the river. This remnant population rarely flowers or produces seed in the wild. The decline of this grass, which is narrowly adapted to high quality, aquifer-fed waters, is the result of drastic draw-downs in the aquifer level to support human population growth in the area, combined with past dredging and vegetation removal, damming, increased siltation and sewage loads, trampling and removal by recreationists, and herbivory by native and introduced waterfowl and by the non-native nutria. Efforts to establish new populations off the San Marcos River using cultivated plants have not been successful.
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
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.
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)
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.
Response to disturbance
Seed dispersal and seedling recruitment
Public education campaign
Restore/maintain the historic flow of the San Marcos River
Be the first to post an update!