Chloroplast DNA extraction from herbaceous and woody plants for direct restriction fragment length polymorphism analysis.

The technique described here is a fast and simple method of extracting chloroplast DNA (cpDNA). It overcomes the need for differential centrifugation using density gradients. The leaves do not have to be kept in the dark and lyophilized before extraction, but lyophilization is still possible. The chloroplasts are specifically lysed in a cell extract of leaves, using a non-ionic detergent. After isolation by centrifugation, the cpDNA is purified by the combined action of proteolytic enzymes and detergents, followed by the elimination of proteins using a mixture of chloroform and isoamyl alcohol. This method provided good quality restriction profiles for all species analyzed.

Microsatellite polymorphism and genetic impact of restocking in mediterranean brown trout (Salmo trutta L.)

The genetic impact of restocking Mediterranean brown trout populations with hatchery stocks was investigated in the Orb River drainage (France), using genetic data from three microsatellite loci. We sampled two wild populations, the main river which is restocked each year and one of its tributaries which has not been restocked for 6 years. Each sample was divided into two age groups (juveniles/adults). Introgression of each native population by hatchery stocks was previously estimated using allele frequencies from two diagnostic protein-coding loci and one mtDNA haplotype. The genetic structure and allelic frequency at three microsatellite loci in native populations were compared with two hatchery samples belonging to stocks usually used for restocking this drainage. High levels of polymorphism (23-27 alleles per locus) were detected for two loci, whereas the third was less polymorphic. Polymorphism was significantly higher in the restocked population than in the now undisturbed population. Significant differences between age groups were observed in the main river, but not in its tributary. The introgression estimates using microsatellites were compared to those obtained from proteins and mtDNA. The different possible origins of alleles common to hatcheries and wild populations (homoplasy, ancestral polymorphism or introgression) are discussed.

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.

Haplotype variation of cpDNA in the agamic grass complex Pennisetum section Brevivalvula (Poaceae).

The Brevivalvula section of the grass polyploid complex Pennisetum shows various reproductive systems, apomixis being the most widespread. Haplotype variation of chloroplast DNA was studied in the six morphological taxa (species) of this section by using RFLP analysis in 54 plants corresponding to 14 elementary taxa, each characterized on the basis of morphology and ploidy level. Two additional species, Pennisetum glaucum and P. purpureum, which belong to another section of the same genus, were analysed for comparison. In Brevivalvula, chloroplast DNA size was estimated to range between 130 and 133 kb. Thirteen of 15 distinct haplotypes identified in the study were specific to the Brevivalvula section. They were unequally distributed among the morphotypes, the ploidy levels and sampling sites. Within the Brevivalvula section, plants of P. setosum, which are perennial and reproduce vegetatively or by agamospermy, possessed a single specific haplotype. This species differed clearly from the five other morphological species, which are known to be annual, to show either sexual or agamospermic reproduction and which shared most of the 12 other haplotypes observed in the section, suggesting the occurrence of multiple hybridization events between the taxa. Chloroplast DNA variation was highly geographically structured, suggesting low seed dispersal between sites, whereas the substantial haplotype diversity observed in the sites may indicate that agamic reproduction is responsible for the maintenance of distinct genetically isolated clones. Haplotype classification using Wagner's parsimony suggested the occurrence of bidirectional gene flow between the diploids and the polyploids, as reported already in other related apomictic complexes.