Résumé
To determine the suitability of several molecular markers for taxonomic studies on the family Phytoseiidae, 5 nuclear and 3 mitochondrial DNA fragments were sequenced for several populations, species, genera, and sub-families. DNA sequences were obtained experimentally or taken from Genbank. Lowest nucleotide divergence was found for the two 18S fragments. No variability was observed between populations of one species (Neoseiulus californicus), between species of one genus, and between two genera of one sub-family. Variation between two sub-families was very low (0.6-1.2%). Poor variability was observed for the two 28S fragments between and within sub-families. Variability was higher for sequences of the fragment ITS-5.8S (intra-genus, 3-7%; inter-genera, 17-20%; inter-subfamily, 29-33%). Variation between intra-species populations was very low for this DNA fragment. Higher nucleotide divergences were obtained for the mitochondrial fragments. For the 12S fragment, the nucleotide divergence rate between two Neoseiulus species was 10%, 25-33% between genera of the same sub-family, and 27-33% between two sub-families. For the fragments of COI, variability between species of a single genus was ca. 20%. Nucleotidic divergence of species belonging to two genera was 26-36% within, and 26-43% between sub-families. Intraspecific variation was low (0-0.4%). The 18S and 28S regions seem to be too conserved for phylogenetic analysis within Phytoseiidae, and would be more suitable for deeper phylogenetic analysis. The mitochondrial fragments are too divergent for robust alignments and phylogenetic analysis between genera of the family, and would be more suitable to assess within-genus systematic studies and species discrimination. The ITS-5.8S fragment seems adequate for phylogenetic analysis within sub-families. However, nucleotide divergence is too high for assessing relationships between sub-families