Tobacco smoking is a risk factor for numerous disorders, including cancers affecting organs outside the respiratory tract. Epidemiological data suggest that smoking is a greater risk factor for these cancers in males compared to females. This observation, together with the fact that males have a higher incidence of, and mortality from, most non-sex-specific cancers, remain unexplained. Loss of chromosome Y (LOY) in blood cells is associated with increased risk of non-hematological tumors. We demonstrate here that smoking is associated with LOY in blood cells in three independent cohorts (TwinGene: odds ratio [OR]=4.3, 95% CI =2.8-6.7; ULSAM: OR=2.4, 95% CI=1.6-3.6; and PIVUS: OR=3.5, 95% CI=1.4-8.4) encompassing a total of 6014 men. The data also suggest that smoking has a transient and dose-dependent mutagenic effect on LOY-status. The finding that smoking induces LOY thus links a preventable risk factor with the most common acquired human mutation.

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Question: We studied the patterns of plant species co‐occurrence on three, nested, spatial scales in semi‐natural grassland communities and explored the possible ecological processes underlying the patterns. Location: Dry, semi‐natural grasslands in a 4.5 km x 4.5 km area on the Baltic Island of Oland (Sweden). Methods: The study used replicated samples on three, nested, spatial scales: 50 cm x 50 cm plots (N= 516), grassland patches (N = 109) and the whole landscape (N= 6). We used a null model approach to study species co‐occurrence patterns and compared the ecological amplitudes of the pairs of species contributing most to the patterns. We used linear models to search for associations between species segregation and environmental and landscape factors. Results and Conclusions: Our results support the prediction that patterns of species co‐occurrence are likely to be influenced by different mechanisms on different spatial scales. On the plot scale, we interpreted the species segregation in terms of species interactions. The degree of species segregation was significantly associated with the plots'positions within the grassland patches (edge effects) and with management intensity of the grasslands ‐ both variables can be assumed to influence species interactions. On the grassland patch scale, we interpreted the species segregation in terms of within‐patch environmental heterogeneity. The degree of segregation was significantly associated with the area of the grassland patches and with management intensity ‐ both variables that are likely to be related to environmental heterogeneity within the grasslands. Species segregation on the landscape scale was interpreted in terms of environmental heterogeneity among grassland patches and was significantly associated with land‐use history.

Summary1 We investigated patterns of allozyme variation in demes of the grass Briza media in semi-natural grassland fragments within a mosaic agricultural landscape on the Baltic island of Öland. In the study area, Briza is both a characteristic species of old pastures and an early colonizer of young grasslands developing on previously forested or arable sites. 2 Generalized linear models revealed that descriptors of both present landscape structure and past grassland history are significant determinants of genetic variation in the Briza demes. Genetic structure and levels of within-deme diversity are influenced by the size of grassland fragments, the type of habitat surrounding the grasslands, the size/ spatial extent of the demes, the geographic position of the demes and the historical continuity of the grassland fragments. 3 Gene diversity ( H ) was higher in demes from grassland polygons with a high proportion of adjacent grassland, higher in the more extensive demes, and decreased northwards within the study area. 4 The negative association between the inbreeding coefficient ( F IS ) and grassland continuity is interpreted in terms of a two-stage colonization process: recruitment into young grasslands leads initially to spatial patchiness, but subsequent selection in maturing pastures occurs within an increasingly uniform and dense sward. 5 Despite a weak overall genetic structure (as indicated by Bayesian cluster analysis) the between-deme F ST was significant. Linear discriminant analysis of within-deme allele frequencies grouped the demes according to the age and previous land-use history of their grassland polygons. The convergence of the allele frequency profiles in the younger grasslands towards those of the old grasslands is consistent with convergence of selective regimes as pastures mature towards an increasingly uniform, dense sward and characteristic species assemblage. 6 The genetic composition of demes of a grassland species appears to be influenced by the process of plant community convergence during grassland development -complementing the recent finding that convergence of species composition in experimental assemblages of grassland plants is dependent on the genotypic composition of the component species.

1600-0706.2002.11907.x General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Within-population gene diversity (H S ) was estimated (using allozyme markers) for 16 populations of the perennial, outcrossing plant, Gypsophila fastigiata, on the Baltic island of O 8 land. The populations were characterized by data on extent, density, life-stages, and habitat diversity. Populations were classed as central or peripheral in relation to the distribution of ''alvar'' (habitats with shallow, calcareous soils on limestone bedrock) on southern O 8 land. Three minimal adequate models were used to explain H S and the proportions of juveniles and dead adults. In the first model, H S was significantly lower in peripheral populations and there were no significant additional effects of other explanatory variables. The lower diversity in peripheral populations can be explained by a combination of genetic drift (in populations that vary in size in response to habitat fragmentation) and lower levels of interpopulation gene flow than in central populations. In the two life-stage models, peripheral populations had significantly larger proportions of both juveniles and dead adultsindicating a greater demographic turnover than in the central populations. There were also significant effects of H S and species diversity on the proportion of juveniles. The central or peripheral position of populations is the strongest predictor of both within-population gene diversity and life-stage dynamics in O 8 land G. fastigiata. M. Lönn, Södertörn Uni6. College,

Using fast-evolving microsatellites, more slowly evolving ITS markers and performing habitat analyses, we demonstrated a drastic genetic divergence and significant habitat differentiation between early- and late-flowering variants of plants morphologically belonging to Gymnadenia conopsea ssp conopsea. The two phenological variants can either be found in separate or in mixed populations. Information from microsatellite markers and ITS sequences indicated the occurrence of an early historical split between the two flowering-time variants, a split that has been maintained until the present time even within sympatric populations. Early-flowering variants were also far more genetically diverse, had more alleles per microsatellite locus and a wider habitat amplitude than late-flowering variants. As a comparison, we included G. odoratissima in the sequencing study. We found G. odoratissima to be most closely related to the early-flowering type. This indicates a more ancient divergence event between the two flowering-time variants within G. conopsea ssp conopsea than between the two different species G. odoratissima and the early-flowering variant of G. conopsea. Possible explanations to the results arrived at and possible mechanisms maintaining the genetic separation are discussed.

Summary 1The grass Festuca ovina is an important constituent of the species-rich`alvar' grasslands on the Baltic island of O È land. Levels of allozyme polymorphism are high and variation is known to be correlated with habitat variation (soil moisture, pH and depth). 2 A 9-year ®eld experiment on species diversity provided replicate plots (in three sites) that had been subjected to six di erent experimental treatments (control; N P K; P K; N K; K; water). 3 Samples of F. ovina were collected and analyses of deviance were used to investigate associations between allele frequencies, at each of four polymorphic loci, and the nutrient/water treatments. We also used the models to estimate predicted values for the alleles in di erent nutrient/water treatments and in interactions involving the nutrient/water treatments and additional explanatory variables (vegetation height and clipping). 4 There were signi®cant allozyme frequency di erences between samples of F. ovina from the six di erent nutrient/water treatments in the grassland experiment. Frequencies in the fertilized or watered plots had diverged from those in the control plots. There were also signi®cant allele±habitat associations (after the removal of site e ects), especially at the Pgi-2 locus. 5 Soil moisture was the only variable that was common to this study and an earlier study of variation in F. ovina in natural habitats. In natural populations, the Pgi-2-2 allele was signi®cantly associated with soil moisture and was more common in dry habitats. Our ®ndings that the frequency of the Pgi-2-2 allele was signi®cantly a ected by the nutrient/water treatments, and that it was rarest in the treatment that involved the addition of extra water, were therefore as predicted. 6 The study supports the conclusion, from an earlier study of populations in unmanipulated grassland habitats, that selection is contributing to the ®ne-scale patterning of genetic variation in the alvar populations of F. ovina.