Genetic diversity of alligator weed in China by RAPD analysis

Abstract

Random amplified polymorphic DNA (RAPD) was applied to analyze genetic diversity of an invasive weedy species, alligator weed (Alternanthera philoxeroides (Martius) Grisebach), collected from eight different sites in southern China. Amplified by 108 RAPD primers, 391 bands were identified from samples collected from three of the eight sites with considerably large spatial intervals, but no genetic variation was detected among the samples. A total number of 196 RAPD fragments were amplified from all samples collected in the eight sites by 31 primers that produced the most consistent results, but no genetic variation was detected within or between populations. The molecular data indicated extremely low genetic diversity in the alligator weed. Given the fact that the alligator weed is a serious invasive weed, and widely found in China, we consider that the low genetic diversity of the alligator weed does not affect the success of its expansion in China, and low genetic diversity does not necessarily lead to endangered status of a plant species. In addition, molecular evidence from this study suggests that the alligator weed in southern China might originate from a very few clones or even only from a single clone. Therefore, the rapid range expansion of the alligator weed is most likely the result of a massive vegetative propagation since it was introduced in China.