Trichogramma and its relationship with Wolbachia: Identification of Trichogramma species, phylogeny, transfer and costs of Wolbachia symbionts

Identification of Trichogramma individuals has long been very difficult. No reliable character was known for the identification of species in this genus, until the utility of male genitalia was recognized in 1968, some 135 years after the first Trichogramma was described ( T.evanescens Westwood, 1833). However, the presence of completelyparthenogeneticlines in this species remained an identification problem because the no reliable female characters exist that allowed identification. The discovery of Wolbachiaas a cause for the complete parthenogenesis in this genus has allowed the identification of such thelytokouslines. Antibiotic treatment couldrevert Wolbachiainfectedthelytokousspecies to sexual ones, thus producing males and allowing their identification in the morphological system. However, the lack of morphological identification of Trichogramma females was only solved with the use of molecular techniques based on rDNAsequencing of the internal transcribed spacer 2 (ITS2) region. Here, this technique was proved to be a reliable tool for the identification of T.cacoeciae , a thelytokousspecies where the parthenogenetic reproduction is not due to Wolbachia infection. In this thesis we report the first record of this species in Peru ( Chapter 2 ). This species is the only thelytokousTrichogramma known in which Wolbachia is not present. T. cacoeciaepresence in South America is discussed. Identification of seventeen native/introduced Trichogramma species using rDNAsequences was done. A molecular key based on restriction analysis allowed identification of the species through the size of the PCR product and the generation of the restriction patterns. Thelytoky in Trichogramma species caused by Wolbachia collected in Peru, Colombia and USA were reported ( Chapter 3 ).Phylogenetic analysis and comparison of DNA sequences of the Wolbachiawsp gene allowed for the recognition of new Wolbachia group "Ato" in the clade of Wolbachia that infect Trichogramma species. The construction ofWolbachia phylogenetic tree showed four distinct groups. The similarities in the Wolbachia sequences for the studied groups suggested the possibility of horizontal transmission between Trichogramma species ( Chapter 4 ). Natural inter- andintraspecifichorizontal transfer of PI Wolbachia between wasps of the genus Trichogramma was shown. Wolbachia infection in uninfected Trichogramma females was possible when infected and uninfected immature wasps shared the same host egg. On the whole, intraspecificinterspecifictransfer ( Chapter 5 ). In T.atopovirilia, Wolbachia infection did not lead to any negative effect on the walking activity, walking speed or other behaviour components studied ( Chapter 6 ).Finally, an overview of the most important outcomes and conclusions of this thesis is presented  ( Chapter 7).