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| 3. |
- Lönn, Mikael, et al.
(författare)
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Gene diversity and demographic turnover in central and peripheral populations of the perennial herb, Gypsophila fastigiata
- 2002
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 99:3, s. 489-498
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Tidskriftsartikel (refereegranskat)abstract
- Within-population gene diversity (HS) was estimated (using allozyme markers) for 16 populations of the perennial, outcrossing plant, Gypsophila fastigiata, on the Baltic island of Öland. 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 Öland. Three minimal adequate models were used to explain HS and the proportions of juveniles and dead adults. In the first model, HS 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 adults – indicating a greater demographic turnover than in the central populations. There were also significant effects of HS 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 Öland G. fastigiata.
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| 4. |
- Malm, J U, et al.
(författare)
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Immigration history and gene dispersal: allozyme variation in Nordic populations of the red campion, Silene dioica (Caryophyllaceae)
- 2002
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 77:1, s. 23-34
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Tidskriftsartikel (refereegranskat)abstract
- Most of the Nordic region was ice-covered during the last (Weichselian) glaciation. During the postglacial period, plant and animal species recolonized the region from several directions and the geographic structuring of genetic variation within Nordic species may still contain a historic component that reflects patterns of postglacial immigration. The present investigation of 69 populations of Silene dioica represents the first large-scale allozyme study of a widespread herbaceous plant in the Nordic region. Although the frequencies of individual alleles showed a range of different geographic patterns, mapping of the axis scores from an ordination of variation at eight polymorphic loci revealed a division into two main geographic groups of populations. The broadly south-western and northeastern distributions of these two groups of populations suggest that immigration into the region may have involved both eastern and southern geographic sources. However, the geographic boundaries between the two groups of populations are diffuse, and the relatively low between-population component of genetic diversity (G(ST) = 16.4%) suggests a history of extensive gene dispersal by pollen. (C) 2002 The Linnean Society of London, Biological Journal of the Linnean Society, 2002, 77, 23-34.
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- Olle, Jonsson B., et al.
(författare)
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Allozyme diversity and geographic variation in the widespread coastal sedge, Carex arenaria
- 2000
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Ingår i: Diversity & distributions. - : Wiley. - 1366-9516 .- 1472-4642. ; 6:2, s. 65-80
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Tidskriftsartikel (refereegranskat)abstract
- Allozyme electrophoresis was used to investigate the structure of genetic variation in the rhizomatous coastal sedge, Carex arenaria, throughout its European range - from the SW Iberian peninsula to the Baltic region. Material was sampled from 77 sites in five geographic regions. Nine of the 13 investigated loci were polymorphic in the total material and there were interregional differences in the number of polymorphic loci per site and the percentage of variable sites. In the Scandinavia/Baltic region only 61% of the sites contained at least one locus with more than one allele, whereas all the British and SW Iberian sites were variable. There was a general tendency for the regional frequencies of the less common alleles at individual loci to decline from SW to NE. The mean (over loci and sites) within-site gene diversity (H(site)) was 0.064 (in calculations based on the number of observed multilocus allozyme genotypes within each sampling site). Although there was considerable variation between geographically adjacent sites, within-site diversity showed a general decrease from SW to NE in Europe. There were significant differences in within-region gene diversity (H(reg)) for the four most variable loci between the five regions. H(reg) generally decreased from SW to NE Europe and most loci showed the highest diversity in the SW Iberian peninsula and the Bay of Biscay regions. The mean (over loci) gene diversity in the total material (H(tot)) was 0.070 and the levels of diversity in Carex arenaria are substantially lower than is usual in rhizomatous sedges. The within-site, between-site and between-regional components of the total diversity were 92.4%, 2.5% and 5.1%, respectively. The low levels of overall gene diversity in C. arenaria and the successive decrease in diversity from SW to NE are interpreted in terms of the species' history of post-glacial spread into northern Europe. Despite the overall northwards decrease in diversity, the widespread occurrence of less common alleles and the lack of regional deviations from Hardy-Weinberg genotype frequency expectations suggest that C. arenaria is not predominantly self-fertilized.
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- Olsson, A, et al.
(författare)
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Morphometric diversity and geographic differentiation in six dogrose taxa (Rosa Sect. Caninae, Rosaceae) from the Nordic countries
- 2001
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Ingår i: Nordic Journal of Botany. - 0107-055X. ; 21:3, s. 225-241
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Tidskriftsartikel (refereegranskat)abstract
- The dogroses (Rosa Sect. Caninae) are characterized by a unique meiosis - the canina meiosis - that results in restricted recombination. In the present study, we investigate population differentiation and morphometric diversity within six taxa, of Nordic dogroses, with the help of automated image analysis of leaflet shape and manually-measured reproductive characters. The total morphometric diversity in each character type was partitioned into its hierarchical components. The within-taxon structure of diversity in leaflet shape is similar (in both rank and magnitude) to the within-taxon structure of reproductive character diversity in all the taxa, with the between-population component of diversity accounting for the majority of the total diversity. The within-taxon structuring of diversity in the dogroses is comparable to that found in selfers and in species characterized by restricted recombination (such as permanent translocation heterozygotes). The relatively high within- and between-family components of diversity in R. dumalis subsp. dumalis may be a reflection of a heterogeneous genome and/or of a higher degree of outcrossing than in the other dogrose taxa. Rosa rubiginosa is characterized by low overall levels of intraspecific variation. There is weak geographic differentiation between populations of R. dumalis subsp. dumalis (in leaflet shape) and R. rubiginosa (in reproductive characters). The study provides no support for the division of R. dumalis into subsp. dumalis and subsp. coriifolia but, in contrast, shows a clear separation between varieties umbelliflora and venusta within R. sherardii.
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| 7. |
- Olsson, Åsa, et al.
(författare)
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Relationships between Nordic dogroses (Rosa L. sect. Caninae, Rosaceae) assessed by RAPDs and elliptic Fourier analysis of leaflet shape
- 2000
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Ingår i: Systematic Botany. - 0363-6445. ; 25:3, s. 511-521
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Tidskriftsartikel (refereegranskat)abstract
- The taxonomy of the dogroses (Rosa sect. Caninae) is notoriously problematic and all the members of the section are characterized by a form of unbalanced meiosis (so-called "canina meiosis"). We used a novel combination of random amplified polymorphic DNA (RAPD) markers and elliptic Fourier analysis of leaflet shape to investigate relationships within and between the seven common dogrose tara in the Nordic countries. A between-individual genetic distance matrix calculated on the basis of the presence/absence of RAPD hands was used in a non-metric multidimensional scaling analysis. Population data from elliptic Fourier analysis of leaflet shape were analyzed with canonical variates analysis. Elliptic Fourier analysis of leaflet shape provided a valuable complement to traditional, often subjectively-assessed, morphological characters and detected subtle patterns of within- and between-taxon differentiation that are generally consistent with the relationships recognized in the current taxonomic treatments of the section. In contrast, RAPDs emphasize the discontinuities between three groups of taxa and suggest that R. canina and the two subspecies of X. dumalis, as well as the taxon-pair A, sherardii and X. villosa subsp. mollis, are more closely related than can be concluded on the basis of morphological characters.
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- Prentice, Honor C, et al.
(författare)
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Allozyme and chloroplast DNA variation in island and mainland populations of the rare Spanish endemic, Silene hifacensis (Caryophyllaceae)
- 2003
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Ingår i: Conservation Genetics. - 1566-0621. ; 4:5, s. 543-555
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Tidskriftsartikel (refereegranskat)abstract
- Silene hifacensis is a narrowly endemic plant, restricted to a few small populations on limestone cliffs in the Spanish province of Alicante and on the Balearic island of Ibiza. The species was collected to extinction in its original mainland location by the early 20th century. Attempts have been made to reintroduce S. hifacensis to this area but conservation efforts are limited by a lack of information on the geographic structure of genetic variation in the species. We used nuclear (allozyme) and chloroplast DNA (cpDNA) PCR/RFLP markers to investigate the structure of genetic variation in 2 mainland and 6 Ibizan populations. Levels of allozyme variation were low, with a mean of 2 alleles per polymorphic locus. Mean (over polymorphic loci) total allozyme diversity (H-tot) was 0.203 and mean within-population diversity (H-pop) was 0.085. Most diversity was explained by the between-population diversity component (G(pop).reg = 57%). Both mainland populations showed allozyme fixation. Three composite cpDNA haplotypes were identified. The first is unique to a mainland population that is also allozymically distinct from all the other populations. The second haplotype is found in the other mainland population and one Ibizan population: these two populations are allozymically identical. The remaining Ibizan populations contain the third haplotype. The geographic distribution of allozymes and cpDNA haplotypes is discussed in terms of population history, dispersal and, speculatively, in terms of the possibility that there has been undocumented translocation of material between populations.
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| 9. |
- Prentice, Honor C, et al.
(författare)
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Changes in allozyme frequencies in Festuca ovina populations after a 9-year nutrient/water experiment
- 2000
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 88:2, s. 331-347
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Tidskriftsartikel (refereegranskat)abstract
- 1 The grass Festuca ovina is an important constituent of the species-rich 'alvar' grasslands on the Baltic island of Oland. 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 field experiment on species diversity provided replicate plots (in three sites) that had been subjected to six different 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 different nutrient/water treatments and in interactions involving the nutrient/water treatments and additional explanatory variables (vegetation height and clipping). 4 There were significant allozyme frequency differences between samples of F. ovina from the six different 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 significant allele-habitat associations (after the removal of site effects), 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 significantly associated with soil moisture and was more common in dry habitats. Our findings that the frequency of the Pgi-2-2 allele was significantly affected 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 fine-scale patterning of genetic variation in the alvar populations of F. ovina.
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| 10. |
- Prentice, Honor C
(författare)
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The Flora of Dorset
- 2002
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Ingår i: BSBI News. - 0309-930X. ; 89, s. 56-57
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Recension (populärvet., debatt m.m.)
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