| Hydrilla verticillata is an invasive, aquatic weed that ranges from Florida to California. Hydrilla is believed to only spread vegetatively. Invasive clonal plants are expected to have low genetic variation limiting their ability to develop resistance to herbicides. Contrary to expectations, hydrilla has recently developed resistance to the herbicide used to control the plant. We used microsatellite loci to determine whether hydrilla is a single clone with low genetic diversity. We found high levels of genetic variation within populations of hydrilla. Spatial patterns of genetic diversity, patterns of genetic differences between individuals, and tests for sexual reproduction, indicate that hydrilla has originated from a single clone. Patterns of genetic diversity suggest that somatic mutations arising during vegetative growth are the main source of genetic diversity. Our study provides an example of how a clonally reproducing organism can potentially develop resistance to herbicides by effectively creating its own genetic diversity. |
