Isolation and characterization of polymorphic microsatellites in the Potato Tuber Moth Tecia solanivora (Povolny, 1973) (Lepidoptera: Gelechiidae).

Nine polymorphic microsatellite markers were isolated from Tecia solanivora, one of the most serious pests of potato tubers in Central and South America. As found in other studies of Lepidoptera, development of microsatellites is a difficult task: in our case, despite the large number of clones sequenced (796), of which 70 were unique, only nine loci were found to be both variable, and in Hardy-Weinberg equilibrium, No null alleles were detected. The loci were tested in three other co-occurring Gelechiidae species, one of which was variable. These loci will be used to provide a greater understanding of the genetic changes occurring during the invasive process in this species.

Microsatellite markers from the Chagas disease vector, Rhodnius prolixus (Hemiptera, Reduviidae), and their applicability to Rhodnius species.

Ten microsatellites were isolated and characterized from a partial genomic library of Rhodnius prolixus, the principal Chagas disease vector in Venezuela, Colombia and Central America. These polymorphic molecular markers could be particularly useful in Chagas disease control initiatives. A wider applicability of the primer-pairs isolated was shown, from 6 to 10 loci being amplifiable in five out of the ten Rhodnius species tested, namely R. domesticus, R. nasutus, R. neglectus, R. neivai and R. robustus. Interestingly, all the loci were amplified in the latter. These markers may be of interest to trace the colonization of human dwellings from triatomine sylvatic populations in order to better define epidemiological risk patterns.

Inference on microsatellite mutation processes in the invasive mite, Varroa destructor, using reversible jump Markov chain Monte Carlo.

Varroa destructor is a parasitic mite of the Eastern honeybee Apis cerana. Fifty years ago, two distinct evolutionary lineages (Korean and Japanese) invaded the Western honeybee Apis mellifera. This haplo-diploid parasite species reproduces mainly through brother-sister matings, a system which largely favors the fixation of new mutations. In a worldwide sample of 225 individuals from 21 locations collected on Western honeybees and analyzed at 19 microsatellite loci, a series of de novo mutations was observed. Using historical data concerning the invasion, this original biological system has been exploited to compare three mutation models with allele size constraints for microsatellite markers: stepwise (SMM) and generalized (GSM) mutation models, and a model with mutation rate increasing exponentially with microsatellite length (ESM). Posterior probabilities of the three models have been estimated for each locus individually using reversible jump Markov Chain Monte Carlo. The relative support of each model varies widely among loci, but the GSM is the only model that always receives at least 9% support, whatever the locus. The analysis also provides robust estimates of mutation parameters for each locus and of the divergence time of the two invasive lineages (67,000 generations with a 90% credibility interval of 35,000-174,000). With an average of 10 generations per year, this divergence time fits with the last post-glacial Korea-Japan land separation.

[Recent hypotheses on the mode of prion propagation in the organism]. / Hypothèses récentes sur le mode de propagation du prion dans l'organisme.

DATA: The prion, which apparently enters the organism via the oral route, crosses the digestive barrier before progressively reaching the brain after multiplying in the lymphoid organs. Dendritic follicles as well as other immune cells appear to be involved in the transfer of prions from the lymphoid organs to the brain. EXPERIENCE: Experimental transfer trials with adoptive murine trembles showed that a fraction of the splenic cells enriched with CD11c+ cells have the highest infectious potential compared with the lymphocyte B enriched cell fraction and the total mononuclear population. PERSPECTIVES: While splenic B cells do not to be able to replicate the prion, their infectious potential is probably the result of contact with dendritic follicular cells, CD11c+ dendritic cells playing an important role in neuroinvasion.

Genetic diversity of the honeybee in Africa: microsatellite and mitochondrial data.

A total of 738 colonies from 64 localities along the African continent have been analysed using the DraI RFLP of the COI-COII mitochondrial region. Mitochondrial DNA of African honeybees appears to be composed of three highly divergent lineages. The African lineage previously reported (named A) is present in almost all the localities except those from north-eastern Africa. In this area, two newly described lineages (called O and Y), putatively originating from the Near East, are observed in high proportion. This suggests an important differentiation of Ethiopian and Egyptian honeybees from those of other African areas. The A lineage is also present in high proportion in populations from the Iberian Peninsula and Sicily. Furthermore, eight populations from Morocco, Guinea, Malawi and South Africa have been assayed with six microsatellite loci and compared to a set of eight additional populations from Europe and the Middle East. The African populations display higher genetic variability than European populations at all microsatellite loci studied thus far. This suggests that African populations have larger effective sizes than European ones. According to their microsatellite allele frequencies, the eight African populations cluster together, but are divided in two subgroups. These are the populations from Morocco and those from the other African countries. The populations from southern Europe show very low levels of 'Africanization' at nuclear microsatellite loci. Because nuclear and mitochondrial DNA often display discordant patterns of differentiation in the honeybee, the use of both kinds of markers is preferable when assessing the phylogeography of Apis mellifera and to determine the taxonomic status of the subspecies.

Population structure and mating biology of the polygynous ponerine ant Gnamptogenys striatula in Brazil.

Gnamptogenys striatula is a polygynous ponerine ant, whose colonies contain either several differentiated queens or several gamergates. Population structure, queen mating frequency and deviation from random mating were investigated in a north-eastern Brazilian population. Eight workers from each of 33 queenright colonies and 17 queens and their progeny (20-40 offspring) were genotyped using eight variable microsatellite markers. Population differentiation tests indicated limited gene flow at the scale of several kilometres, and tests of isolation by distance revealed population viscosity at the scale of a few metres. This population structure, together with the frequent colony migrations and fissions observed in the field, suggest that new nests are founded by budding in G. striatula. Genetic data showed that 13 of our 17 queens were single-mated and four were double-mated. The estimation of the range of maximal frequency of double-mated queens in the population was 0.232-0.259, demonstrating that mating frequency is low in G. striatula. The low estimated mean relatedness between the 17 queens and their mates (-0. 04 +/- 0.49) indicated no evidence of inbreeding in G. striatula.

Evolutionary novelties in islands: Drosophila santomea, a new melanogaster sister species from São Tomé.

The finding of new melanogaster sister species may help us in understanding more about how the emergence of genetic novelties, particularly in insular habitats, can result in speciation. Here we report on the discovery of Drosophila santomea, which is the first melanogaster sibling found off West-equatorial Africa, on São Tomé, one of the Gulf of Guinea islands. Although the eight other melanogaster sister species are remarkably conservative in their morphology except for their terminalia, the new find has a morphological trait distinguishing it from all of these: a pure yellow body coloration of both sexes without the normal black abdominal banding. Evidence from the terminalia, polytene and mitotic chromosomes, period gene and allozymes are provided indicating that it is nonetheless the nearest relative of Drosophila yakuba with which it coexists on the island. The new find is a clear-cut taxon as shown by the production of sterile male hybrids, eventually with developmental defects, in both directions of cross with yakuba and by the existence of an altitudinal divide accompanied by a hybrid zone at mid-elevation on the island. Molecular and karyotypic data further support this conclusion. In contrast to the significant divergence of their nuclear DNAs, an intriguing similarity in their cytochrome b sequences was observed indicating a recent coalescence common to santomea, yakuba and also teissieri cytoplasms. These were shown to harbour the same Wolbachia endosymbiotic bacteria which could possibly be responsible for mitochondrial DNA hitchhiking across the species barrier.