Aim The Quaternary life history of a species determines its current range and the degree and distribution of its present genetic variation. Past climates, ecological relationships and disturbances in connection to evolutionary factors have determined the genetic and geographical distribution patterns of the current vegetation, and consequently, evolutionary processes can be inferred from those patterns. The aim of the present study is to find a plausible evolutionary explanation for the current natural range and genetic variation patterns of Austrocedrus chilensis (D. Don) Florin et Boutelje in Argentina.Location The studied species ranges naturally over a narrow strip not wider than 50 km that runs parallel to the Cordillera de los Andes from 32°39¢ S in Chile to 43°44¢ S in Argentina. The studied populations are located in the Argentine range, especially in its central part.Methods Information on palynological data, current geographical distribution and on amount and distribution of genetic variation of the species in Argentina was the basis for an integrating analysis and discussion.Results Palynological evidence of the past reported the presence of A. chilensis before and immediately after last glaciation on the east side of the Andes. The most conspicuous present populations of A. chilensis are located in areas that were covered by ice during the Last Glacial Maximum. The allelic multiplicity and diversity as well as the population differentiation of the species in Argentina were shown to be small, while the levels of heterozygosity were moderate. A latitudinal gradient trend was recognized as a pattern of distribution of variation in Argentina, the northerly populations being more variable. Extreme marginal populations located in the steppe, out of the glaciated area, show the greatest levels of variation.Main conclusions Evidence was shown supporting that the major factor responsible for the variation pattern found in A. chilensis were the glacial processes. In the Argentine side of the Cordillera de los Andes the species could survive only in a narrow strip between the coldness of the ice sheet and the dryness of the steppe. That implies a generalized genetic drift process. Multiple small refuges in the eastern side of the Cordillera are hypothesized where this cypress would have survived to glaciation. Those refuges are postulated to have been chiefly localized slightly eastward to the present distribution area and most probably in a northern location, at least from 42°S of latitude to the north.

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Different regional patterns of glaciation are expected to have brought about a differential effect on the present genetic structure of natural tree populations in the temperate regions. The aim of the present study is to test this hypothesis in Nothofagus antarctica, a key tree species of the temperate forests of southern South America. An almost continuous ice layer characterized the region of the Andes south of 41 degrees S, while towards northern latitudes the pattern was more fragmented. Therefore, a higher chance for the location of larger or more numerous glacial refuges in the north of the Argentinean range, leads us to predict a higher genetic diversity in this region. Twelve natural populations of N. antarctica were sampled along the northern half of its Argentinean range, including six above 41 degrees S and six below that latitude. Sampled populations were genetically characterized through cpDNA and isozyme gene markers. Both groups of populations were compared by means of several diversity and differentiation parameters. A genetic structure analysis was conducted with isozyme data through clustering and Bayesian approaches. Based on three polymorphic chloroplast regions, only two haplotypes were distinguished, one corresponding to the nine northernmost sampled populations and the other to the two southernmost ones. Only the population located between those two groups resulted polymorphic. AMOVA analyses also revealed a latitudinal genetic structure for the populations surveyed, and higher levels of genetic variation were recognized in the northern populations.

-The genetic control of tree ring growth in Douglas-fir in response to the drought and heat-wave that occurred in 2003 in Europe was studied with microdensity profiles in three clonal experiments located in three different French regions. The drought and heat-wave significantly affected Douglas-fir wood formation. The Chassenoix site (Northeast of Massif-Central) was more severely affected that the other two: the 2003 year-ring was narrower and less dense than in the other sites and than the previous (2002) canicule / Douglas / microdensité / adaptation

SUMMARYIncreasing risks of loosing forest genetic resources and the need for a sustainable quality wood supply make focusing research efforts on undomesticated tree species necessary. The study of their genetic variation in vegetative propagation ability and the development of practical methodologies to obtain genetic copies are essential tools for conservation and breeding programs. patagonian cypress Austrocedrus chilensis is a vulnerable conifer native to the subantarctic forest of South America, with high ecological importance and economical potential. Its genetic diversity, mostly sheltered within unprotected populations, is seriously threatened. This work examined the ability of different genotypes of A. chilensis from xeric, mesic and humid populations to propagate asexually by stem rooting and scion grafting. The influence of exogenous auxins, season of cutting collection, ontogenetic stage of the donor plants, grafting season, and type of scions, was analyzed. Stem rooting ability was found to be poor both for adult (average = 0.27%) and juvenile ortets (average = 2.10%). Only one treatment, a juvenile progeny from a xeric provenance, showed remarkable results with 33.33% of rooting capacity. Grafting showed good results in early spring experiment using vigorous semi-hardwood scions, with an average of 80.95% of successful grafts. Compatibility between genotypes from different provenances used as scion and rootstock was found to be wide. These results indicate that although A. chilensis is a difficult-to-root species, its vegetative propagation by means of scion grafting is feasible using low cost technology.Key words: Austrocedrus, Cupressaceae, stem rooting, scion grafting. RESUMENLos crecientes riesgos de pérdida de recursos genéticos forestales y la necesidad de una producción sostenible de madera de calidad hacen necesario orientar la investigación hacia especies arbóreas nativas no domesticadas. Para rescatar la diversidad genética amenazada y como una importante herramienta para el mejoramiento genético, resulta necesario estudiar la capacidad de las especies para propagarse vegetativamente, así como desarrollar técnicas para obtener copias genéticas. El ciprés de la cordillera (Austrocedrus chilensis) es una conífera vulnerable del bosque subantártico de Sudamérica, de gran importancia ecológica y potencial económico. Su diversidad genética se encuentra seriamente amenazada. En este trabajo se examinó la capacidad de diferentes genotipos de poblaciones xéricas, mésicas y húmedas de A. chilensis, para propagarse asexualmente por enraizado de estacas y por injertos. Se analizó además la influencia de auxinas exógenas, de la estación de colecta, del estadio ontogénico de las plantas donantes, de la estación de injerto y del tipo de púa. La capacidad de enraizado fue muy pobre, tanto para ortets adultos (promedio = 0,27%) como para juveniles (promedio = 2,10%). Sólo una progenie juvenil de procedencia xérica mostró resultados remarcables, con 33% de enraizado. Los injertos mostraron buenos resultado...