Host recombination is dependent on the degree of parasitism.

Parasites and hosts are involved in a continuous coevolutionary process leading to genetic changes in both counterparts. To understand this process, it is necessary to track host responses, one of which could be an increase in sex and recombination, such as is proposed by the Red Queen hypothesis. In this theoretical framework, the inducible recombination hypothesis states that B-chromosomes (genome parasites that prosper in natural populations of many living beings) elicit an increase in host chiasma frequency that is favoured by natural selection because it increases the proportion of recombinant progeny, some of which could be resistant to both B-chromosome effects and B-accumulation in the germline. We have found a clear parallelism between host recombination and the evolutionary status of the B-chromosome polymorphism, which provides explicit evidence for inducible recombination and strong support for the Red Queen hypothesis.

[Direct communication on the Internet. Uninet: the university link for Integrate Telematic Services]. / 'La comunicación en directo en Internet.' UniNet: La RedUniversitaria de Servicios Telemáticos Integrados.

The importance of Internet as a communication medium is clear due to the amount of information it distributes and the high number of potential recipients it has. The appearance of virtual user communities (CMV) focuses to information classification within subjects of interest for certain groups of people in order to facilitate its search and use. The UniNet project of Integrated Telematic Services for CMV through, as well as other subprojects, the 'propuesta RedUni' encourages the creation of CMV by mean of integration of various computer and Internet resources, such as distribution mailing list, web pages, Internet Relay Chat (IRC), etc. The current state of IRC in such context is presented and the utilities of the known as Scientific-IRC as a professional real time communication tool are discussed.

Temporal frequency stability and absence of effects on mating behaviour for an autosomal supernumerary segment in two natural populations of the grasshopper Eyprepocnemis plorans.

Interannual evolution of a polymorphism for a supernumerary segment in the smallest autosome of the grasshopper Eyprepocnemis plorans has been analysed in two natural populations. The polymorphism seemed to be stable in both populations, despite its undertransmission through heterozygous females carrying B chromosomes. Analyses of the effects of the extra segment on mating behaviour failed to show differential mating success in any sex or consistent effects on mating pattern. These results are discussed in relation to the maintenance of this polymorphism in natural populations.

Geographical distribution of B chromosomes in the grasshopper Eyprepocnemis plorans, along a river basin, is mainly shaped by non-selective historical events.

The analysis of 19 populations of the grasshopper Eyprepocnemis plorans, collected along four rivers belonging to the Segura basin (Mundo, Benamor, Taibilla and Segura itself), has shown that the presence of B chromosomes ends abruptly in each river, coinciding with the existence of a narrow pass in which this grasshopper cannot live because of the absence of the appropriate habitats. The existence of a broad inland region lacking grasshoppers with B chromosomes suggests that B chromosomes arose after the first colonization of the Iberian Peninsula by E. plorans specimens from North African populations. The B chromosome seems to have spread upstream along each of these four rivers until reaching geographical barriers that have impeded its advance and thus have preserved the non-B chromosome region. The available evidence indicates that the observed geographical distribution of the B chromosome polymorphism in this zone was shaped mainly by historical non-selective events.