Genetic uniformity of Alternanthera philoxeroides in South China

Summary Alternanthera philoxeroides (Mart.) Grisb is an invasive weed that is widespread in a variety of habitats around the world. It was introduced into China in the 1930s, and today occurs in 20 provinces. The level and pattern of genetic diversity of 193 individuals from 11 land‐grown A. philoxeroides populations from South China were determined using 81 intersimple sequence repeat markers. Mean Nei's gene diversity (HE) was 0.0203 ± 0.008, and total diversity (HT) was 0.0286, indicating that genetic diversity in A. philoxeroides in South China is very low. There was a greater proportion of diversity within populations than among (GST = 0.292) populations. Gene flow (Nm) among populations was 0.607. These results are in accordance with the assumption that populations in South China are genetically depauperate because of the short introduction history and the partially clonal propagation of this weed.