MOLECULAR IDENTIFICATION AND DELIMITATION OF INSECT TAXA: DEVELOPMENT OF NEW DATA, APPROACHES AND EVALUATION OF TOOLS EFFICIENCY

Molecular taxonomy is the science that classifies and identifies organism basing on molecular information. Its application to species-rich groups of organisms, as insects, could improve and accelerate taxa identification and delimitation. The efficiency and the limits of the methods for molecular taxonomy have to be properly evaluated for achieving unbiased results with this taxonomic approach. The main aims of this thesis are: i) to develop COI barcode libraries for Euro-Mediterranean Chrysomelidae identification and test DNA-barcoding efficiency in the identification of the species of the family; ii) to estimate group-specific nucleotide distance thresholds for the molecular identification of Chrysomelidae taxa and compare the error related to their use with the error related to the use of a general threshold value estimated for the whole family; iii) to apply molecular species delimitation methods to other insects taxa with the aim of resolving their taxonomic status in an integrative taxonomy framework; vi) to test the influence of factors intrinsic to the analysed data on molecular species delimitation efficiency. The results obtained confirmed the high efficiency of DNA-Barcoding as tool for Chrysomelidae molecular identification (94-99% efficiency) and the usefulness of molecular delimitation methods in integrative taxonomy for resolving taxonomic debated issues. The use of groups specific thresholds resulted to be related to a significantly lower identification error than the use of a general threshold for the whole Chrysomelidae, suggesting how the use of fixed thresholds for taxa identification is unwise. Finally, some factors, i.e. the species delimitation methods used, the geographic intraspecific distance among individuals collection localities and the difficulties in morphological identification of species, resulted to affect the efficiency of molecular species delimitation.