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Research Project: Identification, Evaluation, and Implementation of Biological Control Agents for Invasive Weeds of Southeastern Ecosystems

Location: Invasive Plant Research Laboratory

Title: Molecular identification of Azolla invasions in Africa: The Azolla specialist, Stenopelmus rufinasus proves to be an excellent taxonomist

item Madeira, Paul
item HILL, M - Rhodes University
item Dray, F Allen
item COETZEE, J - Rhodes University
item PATERSON, I - Rhodes University
item Tipping, Philip

Submitted to: South African Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2016
Publication Date: 7/14/2016
Citation: Madeira, P.T., Hill, M.P., Dray Jr, F.A., Coetzee, J.A., Paterson, I.D., Tipping, P.W. 2016. Molecular identification of Azolla invasions in Africa: The Azolla specialist, Stenopelmus rufinasus proves to be an excellent taxonomist. South African Journal of Botany. 105:299-305.

Interpretive Summary: Use of the beetle Stenopelmus rufinasus to control an invasive floating fern Azolla filiculoides in South Africa appeared to result in feeding damage on a non-target Azolla species. Morphological taxonomy with this plant genus is quite confused and difficult, however. Molecular taxonomy revealed that the non-target Azolla had been misidentified and that the beetle was, in fact, feeding on a known host plant. This work clarified the taxonomy of Azolla species in Africa, and exonerated the biological control program in South Africa.

Technical Abstract: Biological control of Azolla filiculoides in South Africa with the Azolla specialist Stenopelmus rufinasus has been highly successful. However, field surveys showed that the agent utilized another Azolla species, thought to be the native Azolla pinnata subsp. africana, which contradicted host specificity trials. It is notoriously difficult to determine Azolla species based on morphology so genetic analyses were required to confirm the identity of the Azolla used by the agent. Extensive sampling was conducted and samples were sequenced at the trnL-trnF and trnG-trnR chloroplastic regions and the nuclear ITS1 region. Current literature reported A. filiculoides as the only Section Azolla species in southern Africa but 24 samples were identified as Azolla cristata, an introduced species within Section Azolla thatwas not used during host specificity trials. A. pinnata subsp. africanawas only located at one site in southern Africa, while the alien A. pinnata subsp. asiatica was located at three.Whatwas thought to be A. pinnata subsp. africana was in fact A. cristata, a closer relative of A. filiculoides and a suitable host according to specificity trials. This study confirms that S. rufinasus is a proficient Azolla taxonomist but also supports the use of molecular techniques for resolving taxonomic conundrums.