Observations on Zizania texana (Texas Wildrice), an Endangered Species

Edward E. Terrell
William H. Emery
Harold E. Beaty

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Zizania texana is restricted to 2.4 km of the upper San Marcos River in southcentral Texas. Physical and chemical characteristics of the San Marcos River are unusual, being characterized by alkaline or neutral pH and water temperature varying only ca 5 C annually. Taxonomic comparison of Z. texana with Z. aquatica and Z. palustris showed several important morphological differences; these were maintained in cultivation, although Z. texana lost its streaming, submersed habit. Zizania texana is geographically isolated from all other Zizania taxa by at least 640 km. Viable seed obtained in cultivation produced 500 new clones. Human disturbances have affected Z. texana adversely. Survival depends on continued water purity and abundant flow from Spring Lake, source of the river. We are attempting to preserve the habitat and to transplant cultivated clones to other localities in central Texas.