Abstract
This thesis deals with the taxonomy of predatory mites of the family Phytoseiidae, that contains several species used in biological control of pest mites and small insects. The taxonomy of these minute organisms (<500 μm), i.e. specific identification and phylogenetic relationships, is essentially based on morphological characters. These characters, which are sometimes difficult to visualize, interpret (variations in intra and inter-taxa, analogies) and in small numbers, make the identification of species and the current classification questionable. No phylogenetic analysis supports the taxonomy of this family. Moreover, the molecular markers developed up to now are not adapted to define reliable relations between supraspecific taxa. This work aims at: (i) characterizing using molecular markers the identity of two species useful in biological control and establishing molecular decision rules based on several analytical concepts and (ii) determining via the development of new markers the supraspecific relations within the Euseiini tribe and then at the level of the whole family. For the specific diagnosis, this work has shown through the example of Amblyseius swirskii and Phytoseius finitimus the usefulness of integrative approaches including several markers, due to the strong variation in mitochondrial markers at the intraspecific level. Maximum genetic distance values between specimens of the same species (9%, 23% and 2.8% for 12S rRNA, CYTB DNA mt and ITSS) were established. Concerning supraspecific relationships, new molecular markers have been developed. The combination of six molecular markers (12S rRNA, CYTB DNA mt, COI DNA mt, ITSS, 28S rRNA, and HSP90) now allows resolving different supraspecific ranks to be investigated. The application of these markers to the tribe Euseiini and to the family shows that certain taxa were valid. For example, this work emphasizes the monophyly of the Euseiini and representatives of the sub-tribes considered. The genus Iphiseius seems to not be valid and is included in the genus Euseius. Morphological, biogeographical and ecological analyses (host plants) carried out at the level of the whole tribe on the basis of a bibliographic compilation, emphasized the West Gondwanaland origin of this taxon on plants of Rosidae and the evolution of certain morphological characters. This thesis opens new insights for studying the relationships between the genera of Phytoseiidae due to the new markers developed. Studies should continue to (i) extend the panel of available markers and (ii) increase the sampling of species to be included in analyses related to their bio-ecological characteristics in order to determine how phylogenetic relationships can predict interesting life traits for biological control implementation (prey, plants, alternative food).