Genetic diversity assessment of in situ and ex situ Texas wild rice (Zizania texana) populations, an endangered plant


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January 2017


Texas wild rice (Zizania texana) is an endangered, aquatic perennial plant endemic to the upper section of the San Marcos River, Texas. Ex situ populations of Z. texana are maintained by the U.S. Fish and Wildlife Service in the event of a catastrophe event. We analyzed the genetics of in situ and ex situ populations of Z. texana to address the following questions: (1) are in situ populations adequately represented in ex situ population? (2) Is there genetic diversity among the current in situ population? (3) Has the current in situ genetic diversity increased or decreased from historical estimates in 2007. Results indicated that the overall ex situ populations were lower in genetic (allelic) diversity compared to the in situ population, with some in situ populations not present in the refugia. Overall, heterozygosity was moderate and ranged from HO = 0.530 to HO = 0.635 in the wild and HO = 0.549 to HO = 0.727 in the ex situ population. Inbreeding coefficients (FIS) were near zero or negative indicating that inbreeding is not common within the current populations (in situ and ex situ) suggesting that some populations have an excess of heterozygotes (negative FIS). Analysis of current in situ population structure indicated there are three unique genetic clusters in the San Marcos River. Comparison of the in situ population with historical analysis indicates the genetic diversity of the wild population is dynamic both temporally and spatially. The results indicate that Z. texana exhibits a plastic reproductive system utilizing both asexual (vegetative) and sexual (flowering and seed production) reproduction.


Genetics, Endangered Species, Refugia, San Marcos River, Texas Wild Rice

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Aquatic Botany, Vol. 136 (2017-01).