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Aim Long-term climatic variation has generated historical expansions and contractions of species ranges, with accompanying fragmentation and population bottlenecks, which are evidenced by spatial variation in genetic structure of populations. We examine here hypotheses concerning dispersal and vicariance in response to historical geoclimatic change and potential isolation produced by mountains and water barriers.Location The temperate rain forest of southern South America, which is distributed from coastal Chile, including the large continental island of Chiloé, across the Andes into Argentina.Methods We investigated our hypotheses in the phylogenetically and biogeographically relictual marsupial Dromiciops gliroides. We examined 56 specimens, which resulted from field samples and museum study skins from 21 localities. We evaluated the influence of two major barriers, the Andean cordillera and the waterway between the mainland and the large island of Chiloé, by performing Bayesian and maximum-likelihood phylogenetic analyses on sequences of 877 base pairs of mitochondrial DNA. We further tested the contribution of the proposed geographical barriers using analysis of molecular variance (amova). We also evaluated the responses of populations to historical north-south shifts of habitat associated with glacial history and sea-level change.Results Our analyses revealed a phylogeny with three clades, two of which are widespread and contain nearly all the haplotypes: a northern clade (36-39°S) and a southern clade (40-43°S). These two clades contain forms from both sides of the Andes. Within the southern clade, island and mainland forms were not significantly differentiated. Tests of recent demographic change revealed that southern populations have experienced recent expansion, whereas northern populations exhibit long-term stability. The direction of recent gene flow and range expansion is predominantly from Chile to Argentina, with a modest reciprocal exchange across the Andes. Recent gene flow from the island of Chiloé to the mainland is also supported. Main conclusionsThe genetic structure of contemporary D. gliroides populations suggests recent gene flow across the Andes and between the mainland and the island of Chiloé. Differences in demographic history that we detected between northern and southern populations have resulted from historical southward shifts of habitat associated with glacial recession in South America. Our results add to a growing literature that demonstrates the value of genetic data to illuminate how environmental history shapes species range and population structure.

Our aim was to analyze the incidence of mutations in BRCA1 and BRCA2 genes in 54 families with breast/ovarian cancer. Families were selected from three Institutions following the standard criteria for hereditary breast/ovarian cancer. PCR amplification of all exons was performed, followed by SSCP, heteroduplex, PTT and sequencing analysis. We identified eight truncation mutations, three in the BRCA1 gene and five in the BRCA2 gene. Three of these mutations have not been reported previously by other groups: 308insA in one family, 3936 C>T in two families, for BRCA1, and 4970insTG in one family for BRCA2. In addition two families having Ashkenazi Jewish ancestors present the well known mutations 185delAG and 6174delT. Interestingly, 5 out of 11 families have mutations recurrent in Spanish families. Among the 54 families selected, seven have breast and ovary cancer cases, and only two presented a mutation in BRCA1 or BRCA2 genes. Other cancers as prostate and stomach are frequent among relatives carrying the mutation. Five cases of very early onset (<31 years old) breast cancer were detected. The frequencies of BRCA1 (0.074) and BRCA2 (0.13) mutations in our families is low but similar to the incidence found in other populations, like in Spain. Since is widely known that risk factors that modulate the development of breast cancer such as lifestyle risk factors, geographic location, country of origin and socioeconomic status, besides a familial history of breast cancer our findings suggest that the history of colonization and immigrations is very relevant when studying hereditary factors associated to breast cancer.

The spectrum of doubly ionized xenon has been investigated. The study is based on photographic recordings of xenon spectra in the 490-8900 À range. The number o f classified lines has been increased from about 300 to about 1400. The lines have been classified as transitions between 73 even levels belonging to the 5s2 Sp4, S^Sp^ôp, 4/, 5 / and 5r°5/>6 configurations, and 83 odd levels belonging to the 5sSps, 5s15/r* 6s, 7s, 5d and 6d configurations. All the experimentally established Xe I I I levels are given in Tables I I and III. The level values were determined by a least-squares procedure in which the appropriately weighted wave numbers of the identified lines were used as input. All level designations are in LS notation. In most cases the names given to the levels were taken from least-squares fits of the theoretical energy expressions to the experimentally observed level values. In general, the calculated purities of the states 41Physica Scripta. Vol. 38, 347-369, 1988. A large number of strong xenon laser lines were reported some 20 years ago [9]. Primarily due to the work of the group in La Plata, the laser lines were classified as originating in doubly and trebly ionized xenon, but no further classifica tions were possible due to the lack of relevant spectroscopic data.In W. P ersson, C . -G . W ahlstrôm , G . B ertuccelli, H . O. D i R o cco , J. G. R eyn a A lm an dos an d M . G allardoWhen performing the analysis of the experimental data we were guided by theoretical predictions of the level structures. Such predictions were obtained by diagonalization of the appropriate energy matrices, including C l matrix elements. The radial parts of the matrix elements were determined in Hartree-Fock calculations. Approximate scaling factors were determined from comparisons with calculations for similar structures. Figure 1 shows the relative positions and extensions of the configurations studied. The levels in 5s25p*, 5s5p5 and 5sP5p6 were known from earlier investigations, though the designation of one level, 5s5ps X P X has been revised. The 5s15pi n l configurations can be considered as being built on the ground configuration of Xe IV, 5s? 5p3, with the addition of an outer electron. The parent configur ation gives three terms, namely 4 S', 2D and 2P . Almost all levels of the 5s25pi 6p, 6s and 5d configurations have been experimentally established or verified in this work. In the 4/ configuration, five of the levels based on the 2P parent term are missing and in the 5s2 5p* 7s and configurations only levels based on the 4S and 2D parent terms have been located. In the 5/configuration, only the levels belonging to the lowest term, C S )SF, have been located with certainty. Figure 1 shows that there is severe overlapping of con figurations of the same parity. This leads to heavy mixing of states belonging to different configurations, even if the matrix elements connecting the states are small. Such mixing occurs between 6 5 and 5d, 7s and 6 d and between 6 p and 4/ states. Even configurationsWhen interpreting...