Introduction and Motivations Sample Clauses

Introduction and Motivations. Cytoplasmic Incompatibility (CI) refers to one solution adopted by intracellular parasites such as Wolbachia or Cardinium hertigii [47, 51] to spread themselves among the hosts they infect by interfering with the breeding process, preventing the formation of a healthy offspring with the uninfected host. The phenomenon has been noticed by Xxxxxxxx [59] in the late 30’s who observed that some male mosquito strains of Culex pipiens failed to accomplish a breeding with females of another strain, while the breeding between females of the first strain and males of the second one was successful. We will take as example of this phenomenon the bacterium Wolbachia and describe some characteristics, aspects and models related to CI. Wolbachia is an endosymbiont (i.e. an organism that lives within the cells of another) which lives in the gametes of many insects which act as their hosts [50]. To underline the extent of interest in this phenomenon and in Wolbachia, observe that it is believed Wolbachia has an incidence of infection of 67% among all the insect species [50] with a slightly higher prevalence among arthropods [77]. These data are interesting for their prospective applications as insect pest control or gene spreading among the population. One of the main scientific interests of Cytoplasmic Incompatibility is the possibility to reduce the population size of the hosts or employ the parasite as a vector to spread some genes among the population. Indeed, as done in experiments with Culex pipiens [56] and the medfly Ceratitis capitata [56], by releasing in the population a huge quantity of infected males it is possible to reduce the size of the next generation population. Different approaches to reduce the size of the population are obtained by employing CI-inducing bacteria which may reduce the lifespan of the infected host as experimentally done for the mosquito A. aegypti [61]. Finally, another source of interest is the presumed capability of CI to induce a speci- ation in the host population [88]. Indeed, the impossibility to breed between two popula- tions with incompatible infections may promote a higher genetic variation between them than within each population. Speciation events and the phenomenom of coevolution are also in the center of our interest in Chapter 2. Fem wHa Fem wNo Fem wRi Fem (uninfected) Table 1.1: Bidirectional CI in Drosophilia simulans Furthermore, Wolbachia may provide a positive effect on the fitness of infected ele- ments in the population...