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

Abstract

Z. texana is restricted to 2.4 km of the upper San Marcos River in southcentral Texas [USA]. Physical and chemical characteristics of the San Marcos River are unusual, being characterized by alkaline or neutral pH and water temperature varying only approximately 5.degree. 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. Z. 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 affected Z. texana adversely. Survival depends on continued water purity and abundant flow from Spring Lake, source of the river. Attempts to preserve the habitat and to transplant cultivated clones to other localities in central Texas are being evaluated.