Molecular biology for Phytoseiidae identification: preliminary results

The Phytoseiidae has stirred a great interest since the 1950's as the role of a few efficient species in the biological control of tetranychid mites has been emphasized. Whereas only less than 30 species were known in 1951, more than 2,000 have been described up to now. Species description is only based on a morphological species definition. The characters commonly used are the length of idiosomal setae, the extension level of peritreme, the dentition of chelicerae, the shape of the insemination apparatus or "spermatheca" and of the ventrianal shield. However, intermediate morphological patterns between two species could exist. Furthermore, differences could be sometimes very tiny, could concern only one character, and nothing is known about the reliability of these morphological characters in Phytoseiidae diagnostic. Finally, mites are microscopic organisms and very few characters are available to distinguish between species. The aims of this study are (1) to determine how molecular tools could be useful for diagnostic of Phytoseiidae at species level, and thus (2) to assess the reliability of the morphological differences usually used to discriminate species entities. This work is developed in the framework of recent widely proposals developed to use the sequences of mitochondrial DNA fragments (Cytochrome Oxydase 1) to identify specimens across all the Tree of life and branded ''DNA barcoding''. This process requires to show a very low frequency of divergence within a species, but a significant divergence at higher taxonomic levels. In this work, two mitochondrial DNA fragments, COI and 12S, were sequenced for three species of Phytoseiidae (Neoseiulus californicus, Kampimodromus aberrans and Euseius stipulatus) and relatives. The aim is to evaluate intraspecific and interspecific genetic distances for separating sympatric and morphogically close species. The results presented here are preliminary and show on one hand the difficulty to obtain COI sequences and on the other hand the good reliability of the 12S sequences for the diagnostic of the species considered