Genetic diversity of Potamogeton maackianus in the Yangtze River

The genetic diversity and genetic structure of Potamogeton maackianus A. Berm. in seven lakes of the middle reaches of the Yangtze River were studied using random amplified polymorphic DNA (RAPD). The gene flow and genetic relationships between populations were analyzed in combination with the geographic distribution and the river system of the lakes. A total of 112 bands were amplified and 59 bands (52.7%) were polymorphic. Each of the 86 individuals investigated exhibited a unique genotype. The Shannon index was used to measure genetic diversity, and the total genetic diversity was 0.414 and the mean genetic diversity of populations was 0.148. P. maackianus showed a relatively high level of genetic diversity. Analyses of molecular variance (AMOVA) revealed that 63.8% of the total genetic diversity existed among populations and 36.2% within them, which was consistent with the genetic structure computed by the Shannon index: among-population variation and within population variation accounted for 64.4 and 35.7%, respectively. The gene flow among populations was very limited, and genetic isolation among populations occurred even though they were connected through the Yangtze River. Cluster analysis divided the seven populations into two groups, and the genetic relationships among the populations had no obvious association with their geographic distribution, or the historical relations with the river system of the lakes where they occurred. Mantel tests revealed that distance was an important factor affecting the genetic structure in populations. The development history of P. maackianus populations in Honghu Lake had an obvious effect on its genetic structure. (C) 2004 Elsevier B.V. All rights reserved.