Submitted to: Aquatic Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/26/2007
Publication Date: 6/8/2007
Citation: Madeira, P.T., Coetzee, J.A., Center, T.D., White, E.E., Tipping, P.W. 2007. The origin of Hydrilla verticillata recently discovered at a South African dam. Aquatic Botany. 87:176-180 Interpretive Summary: In February 2006 the invasive aquatic weed hydrilla was discovered in KwaZulu-Natal, South Africa along the Pongolapoort Dam on the Pongola River. Its presence there threatens a multimillion rand fishing and tourism industry. The South African Plant Protection Research Institute initiated control measures, a survey of the surrounding area and a biological control project. They also contacted scientists at the USDA-ARS Invasive Plant Research Lab for assistance in identifying the geographic origin of the hydrilla. When biological control agents are gathered from the same region as the weed it increases the chance of successful control because the insect has co-evolved with the plant and therefore has a better chance of thriving. A chloroplast DNA sequence was obtained for thirty-four hydrilla samples from around the world and compared. The sequences formed groupings of similarity called clusters. These clusters agreed with those of a previous molecular study which used a different tool called RAPD. The South African plant appeared in the cluster with plants from Malaysia and Indonesia. Information from the South African aquatic plant industry indicates that most of their aquatic plants originate from Malaysian suppliers.
Technical Abstract: Hydrilla was discovered during February 2006 at the Pongolapoort Dam on the Pongola River, KwaZulu-Natal, South Africa. Its presence there threatens a multimillion rand fishing and tourism industry. The South African Plant Protection Research Institute initiated control measures, a survey of the surrounding area, a biological control project using two species of ephydrid flies (Hydrellia), and, in collaboration with the USDA-ARS Invasive Plant Research Lab, a project to determine the origin of the infestation using molecular analysis. Four South African plants along with 30 others from around the world were analyzed using the trnL intron and trnL-F intergenic spacer of the chloroplast. The sequence data produced almost identical major clusters as earlier RAPD data. While incapable of much definition within the clusters, the sequence data is superior in defining the relationships between clusters. The South African specimens clustered with Malaysian and Indonesian samples. This is in accordance with interviews of aquatic plant dealers who identified Malaysia as a major source of aquatic species for the trade in South Africa