Molecular studies on the species complex of Trichosirocalus horridus in the biological control of Carduinae weeds

The genus Trichosirocalus Colonnelli, 1979, (Coleoptera, Curculionidae, Ceutorhynchinae) includes 17 Palaearctic species mainly feeding on Plantaginaceae and Asteraceae. We studied the taxonomic status of the species complex of Trichosirocalus horridus (TH) by means of molecular markers. We used both mithochondrial (cox1) and nuclear (ef1 ) markers that carried a common phylogenetic signal useful to clarify the taxonomic status of the investigated species. TH was recognized as a single species until 2002, when it was split in three species: T. horridus, T. briesei and T. mortadelo. Our findings challenge this taxonomic framework suggesting the existence of only two distinct species, i.e. T. horridus and T. briesei. A thorough morphological analysis is in progress in order to clarify the nomenclature of the species complex. Moreover, the nuclear gene for the ef1 has proven to be highly informative for detecting putative introgression/hybridization events showing that genetic screenings of natural populations of potential agents for biological control of weeds are of paramount importance in assessing the possibility of using specimens belonging to the T. horridus complex for the control of thistle weeds.