Mikael Lönn

ASSOCIATIONS BETWEEN ALLELE FREQUENCIES IN FESTUCA-OVINA AND HABITAT VARIATION IN THE ALVAR GRASSLANDS ON THE BALTIC ISLAND OF OLAND

1 If different genotypes have different relative fitnesses in different habitats, genetic diversity may be maintained in local populations by habitat selection. The spatial structuring of genetic variation within plant populations will thus be associated

Smoking is associated with mosaic loss of chromosome Y

Men beware, when smoke gets in your Ys The relationship between tobacco smoking and elevated cancer risk has been recognized for 60 years. Yet what smoking does to our genetic material is still not fully understood. New work suggests that men should be particularly concerned. In a study of over 6000 men, Dumanski et al. find that men who smoke are more than three times as likely as nonsmokers to show loss of the Y chromosome in their blood cells. Whether this is a causal factor in cancer development or simply a marker of more consequential damage on other chromosomes could not be deduced from the study. Science, this issue p. 81 Men who smoke are over three times more likely than nonsmokers to show loss of the Y chromosome in their blood cells. 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 with females. This observation, together with the fact that males have a higher incidence of and mortality from most non–sex-specific cancers, remains unexplained. Loss of chromosome Y (LOY) in blood cells is associated with increased risk of nonhematological tumors. We demonstrate here that smoking is associated with LOY in blood cells in three independent cohorts [TwinGene: odds ratio (OR) = 4.3, 95% confidence interval (CI) = 2.8 to 6.7; Uppsala Longitudinal Study of Adult Men: OR = 2.4, 95% CI = 1.6 to 3.6; and Prospective Investigation of the Vasculature in Uppsala Seniors: OR = 3.5, 95% CI = 1.4 to 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.

Genetic structure and allozyme-microhabitat associations in Bromus hordeaceus.

Genetic variation at alcohol dehydrogenase and phosphoglucoisomerase loci in Bromus hordeaceus on the Baltic island of Oland shows substantial spatial structuring among sites several km apart but also among plots within sites on a scale less than ten m. Oland habitats occupied by B. hordeaceus consist of a fine-scale mosaic in which thin soils on well-drained calcareous bedrock are interspersed with depressions containing deeper soil and subject to seasonal water logging. Among sites, the frequency of the Adh-1b-S allele was significantly associated with soil depth and with the cover of mosses and of grasses. The frequency of the Pgi-1b-F allele was significantly associated with soil depth and the Pgi-1b-M allele was significantly associated with soil depth and with the cover of mosses, lichen and grasses (...)

Genetic differentiation and habitat preference of flowering-time variants within Gymnadenia conopsea

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.

Genetic structure, allozyme-habitat associations and reproductive fitness in Gypsophila fastigiata (Caryophyllaceae)

Relationships between allozyme differentiation, habitat variation and individual reproductive success were examined in local populations of a perennial herb, Gypsophila fastigiata, on the Baltic island of Öland (Sweden). Relatively little (c. 2%) of the total allozyme diversity in this largely outcrossing species is explained by differentiation between sites tens of kilometres apart. The low level of geographic differentiation suggests that gene flow between sites is, or has recently been, extensive. Yet the component of allozyme diversity due to differentiation between plots (only tens of meters apart) within sites is 3 times larger than the between-site component of diversity. Allozyme variation, especially at the Pgi-2 locus, is significantly associated with habitat variation within sites. Different allele x habitat combinations for the Pgi-2 locus are associated with differences in individual reproductive fitness. Differential selection in different local habitats may thus contribute to the fine-scale structuring of genetic diversity within sites.

Local‐scale genetic structure in the peatmoss Sphagnum fuscum

Sphagnum (peatmoss) dominates huge areas of the Northern Hemisphere and acts as a significant carbon sink on a global scale, yet little is known about the genetic structure of Sphagnum populations. We investigated genetic structure within a population of the common peatmoss Sphagnum fuscum, to assess local patterns of genetic diversity and the spatial extent of clones. One hundred seventeen shoots were sampled from five transects in Fuglmyra, central Norway, and sequenced for three anonymous DNA regions. Five neighbourhood patches were marked along each transect, and from each patch, five stems were sampled for molecular analyses. Seventeen haplotypes could be distinguished and two major groups of haplotypes differed by 12 mutational steps. The two major haplotype groups differed significantly in microhabitat association along the distance to groundwater table and the pH gradients, indicating microhabitat differentiation. The haplotypes within these groups were all genetically similar, differing by one or two mutations. The most common haplotype occurred in four transects separated by 250‐m distance. Most of the molecular variation in the population was found among transects, and within patches. Large dominating clones within each transect resulted in low variation explained by the among‐patch‐within‐transect component of spatial structure. Mutation appears to account for a larger proportion of the population variation than recombination. Within the population, vegetative growth and asexual reproduction from gametophyte fragments dominate as the main reproductive mode.

Genetic structure in two meadow varieties of Euphrasia stricta on the Baltic island of Gotland (Sweden) and implications for conservation

The annual hemiparasiteEuphrasia stricta occurs on Gotland in two early-flowering meadow varieties.E. stricta var.suecica is on the Swedish red-list as endangered, occurring in Sweden only on the Baltic island of Gotland. It probably has near relatives east of the Baltic proper. The other variety,E. stricta var.tenuis, has a wider distribution occurring almost all over Sweden, but is declining in abundance. Both varieties have close morphological similarities and habitat preferences, raising questions about which level conservation efforts should be focused on, varieties or populations. In this study we describe the genetic structure between and within these two varieties using amplified fragment length polymorphism, AFLP.FST between varieties is 0.14, and between populations within the varietiesE. stricta var.suecica and var.tenuis FST is 0.60 and 0.26 respectively. The partitioning of gene diversity to different levels shows that 14% of the genetic diversity occurs between varieties, 42% between populations within varieties, and 44% within populations. Significant genetic differentiation was detected between varieties, populations and subpopulations within populations using a constrained principal coordinate analysis.We suggest that all of the existing populations of these two varieties on Gotland should be preserved, since they are few (6E. stricta var.suecica and 5E. stricta var.tenuis) and much of the genetic diversity is partitioned between populations.

A horizontally transferred nuclear gene is associated with microhabitat variation in a natural plant population.

Horizontal gene transfer involves the non-sexual interspecific transmission of genetic material. Even if they are initially functional, horizontally transferred genes are expected to deteriorate into non-expressed pseudogenes, unless they become adaptively relevant in the recipient organism. However, little is known about the distributions of natural transgenes within wild species or the adaptive significance of natural transgenes within wild populations. Here, we examine the distribution of a natural plant-to-plant nuclear transgene in relation to environmental variation within a wild population. Festuca ovina is polymorphic for an extra (second) expressed copy of the nuclear gene (PgiC) encoding cytosolic phosphoglucose isomerase, with the extra PgiC locus having been acquired horizontally from the distantly related grass genus Poa. We investigated variation at PgiC in samples of F. ovina from a fine-scale, repeating patchwork of grassland microhabitats, replicated within spatially separated sites. Even after accounting for spatial effects, the distributions of F. ovina individuals carrying the additional PgiC locus, and one of the enzyme products encoded by the locus, are significantly associated with fine-scale habitat variation. Our results suggest that the PgiC transgene contributes, together with the unlinked ‘native’ PgiC locus, to local adaptation to a fine-scale mosaic of edaphic and biotic grassland microhabitats.

Genetic divergence of climatically marginal populations of Vicia pisiformis on the Scandinavian Peninsula

Vicia pisiformis L. is a perennial leguminous plant with a main distribution in broadleaved forest-steppes of eastern Europe. The species is classified as endangered (EN) according to the IUCN red-lists in both Norway and Sweden, due to severe fragmentation, small population sizes and continuing population decline. The populations on the Scandinavian Peninsula constitute the northern limit of the species distribution and are mostly restricted to warm stony slopes with predominantly southern aspects. In this study we used the AFLP method, which is a high-resolution genetic fingerprint method. Samples were collected from 22 Scandinavian populations. The overall genetic structure was analysed in an AMOVA, in a Mantel test and through constrained correspondence analysis (CCA). The ordination scores representing non-geographic genetic divergence were extracted from the CCA and analysed in a linear model using habitat variables and population size as explanatory variables. We found (i) a strong geographic structure, (ii) significant genetic divergence between populations, (iii) that this genetic divergence remained significant even after removing the effect of geography in a partial CCA and (iv) that the remaining non-geographic part of genetic divergence (distance from the ordination centre) was associated with aspect, populations with a northern aspect were more genetically divergent. Aspect explains more variation than population size and is the only variable retained in the minimal adequate model. We suggest that local adaptation has caused this divergence from an expected geographical pattern of genetic variation. This explanation is further supported by the association between aspect and specific AFLP fragments.

Sewage treatment plant associated genetic differentiation in the blue mussel from the Baltic Sea and Swedish west coast

Human-derived environmental pollutants and nutrients that reach the aquatic environment through sewage effluents, agricultural and industrial processes are constantly contributing to environmental changes that serve as drivers for adaptive responses and evolutionary changes in many taxa. In this study, we examined how two types of point sources of aquatic environmental pollution, harbors and sewage treatment plants, affect gene diversity and genetic differentiation in the blue mussel in the Baltic Sea area and off the Swedish west coast (Skagerrak). Reference sites (REF) were geographically paired with sites from sewage treatments plant (STP) and harbors (HAR) with a nested sampling scheme, and genetic differentiation was evaluated using a high-resolution marker amplified fragment length polymorphism (AFLP). This study showed that genetic composition in the Baltic Sea blue mussel was associated with exposure to sewage treatment plant effluents. In addition, mussel populations from harbors were genetically divergent, in contrast to the sewage treatment plant populations, suggesting that there is an effect of pollution from harbors but that the direction is divergent and site specific, while the pollution effect from sewage treatment plants on the genetic composition of blue mussel populations acts in the same direction in the investigated sites.