Lysathia flavipes and Lysathia cilliersae Cabrera sp. nov. (Coleoptera, Chrysomelidae): genetic and morphological unravelling of biocontrol agents for two invasive aquatic plants

In the search for specific natural enemies to control two invasive aquatic plants (IAP) from South America, Ludwigiagrandiflorasubsp.hexapetala (Onagraceae) and <i>Myriophyllumaquaticum</i> (Haloragaceae), taxonomic challenges associated with two <i>Lysathia</i> Bechyné, 1959 (Chrysomelidae; Alticini) species had to be resolved. <i>Lysathiaflavipes</i> (Boheman, 1859) exhibits significant morphological variation, causes heavy damage to both IAPs, and may represent more than one species due to the phylogenetic gap between hosts. Additionally, an undescribed <i>Lysathia</i> species (previously published as <i>Lysathia</i> sp.), sourced from Brazil, has been successfully used as a control agent for <i>M.aquaticum</i> in South Africa since 1994. An integrative taxonomic approach combining genetic and morphological analyses was employed. A lectotype and paralectotypes for <i>Graptoderaflavipes</i> Boheman, 1859 are here designated. Phylogenetic studies revealed that <i>L.flavipes</i> had greater genetic and morphological variation than originally described, and no evidence suggested that <i>L.flavipes</i> represented a species complex associated with its host plants. As a result, the species description was expanded. On the other hand, genetic and morphological differences such as body size, colouration, and genital structures further supported the description of <i>Lysathiacilliersae</i> Cabrera, <b>sp. nov.</b> and its differentiation from other closely related species, including <i>L.flavipes</i> and <i>L.ludoviciana</i> (Fall, 1910). Specimens of <i>L.cilliersae</i> <b>sp. nov.</b> collected in Misiones, Argentina, matched those from South Africa. Genetic sequences correlated with morphological vouchers, images, and illustrations of morphology and genitalia, as well as new distribution records, are provided. This research contributes to the taxonomic knowledge of the <i>Lysathia</i> genus and supports accurate species identification in applied entomological contexts, such as biological control programmes.