1,721,094 research outputs found
Håkan Tegelström ('HåTe'): naturalist and geneticist 2 August 1947-20 March 2004 - Obituary
No full textReproductive system and population structure in three arctic Saxifraga species
No full textSaxifraga cespitosa, S. tenuis and S. cernua were examined in the Abisko area, N Sweden. Populations of S. cespitosa were gynodioecious. Hermaphrodite individuals showed a high selfing efficiency and low pollen:ovule ratios, consistent with a lower outbreeding rate. Saxifraa tenuis was hermaphrodite with some indication of sexual asymmetry. Pollen:ovule ratios were low, but the ability to set seed by autodeposition was lower in S. tenuis than in S. cespitosa. Saxifraga cernua was androdioecious, with some populations that contained only female-sterile individuals and other populations with both female-sterile and hermaphrodite individuals. The higher production of bulbils by female-sterile individuals, coupled with self-incompatibility in hermaphrodites, suggests a means by which androdioecy may be maintained in S. cernua, in the absence of differences in male reproductive success between gender classes. Although all three species showed significant inter-population differentiation, the morphometric distances between populations were not related to the geographic distances between populations. Most of the total diversity in leaf shape was accounted for by inter-population differentiation in all three species, with <1% of the diversity due to variation within individuals. The mosaic pattern of variation in the three saxifrages is consistent with a scenario of localized founder effect and may still reflect patterns of recruitment after the deglaciation of the study area c8200BP. -from Author
Immigration history and gene dispersal: allozyme variation in Nordic populations of the red campion, Silene dioica (Caryophyllaceae)
No full textMost 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
Morphometric variation in a hybrid zone between the weed, Silene vulgaris, and the endemic, Silene uniflora ssp petraea (Caryophyllaceae), on the Baltic island of Oland
Full text linkOn the island of Oland the weed, Silene vulgaris (Moench) Garcke, and the endemic, Silene uniflora Roth ssp. petraea, hybridize when brought into contact by anthropogenic disturbance. Variation was studied in transects across a hybrid zone where a linear population of S. vulgaris crossed the native habitat of S. uniflora ssp. petraea. Plants were scored for 20 morphological characters. Although individual characters showed clinal trends between weed and endemic, all plants were assignable to one or other parental species. Only 14% of the 554 scored plants showed intermediacy in one or a few characters, and ordinations showed two separate groups of samples. The low number of intermediates is discussed in terms of character choice, habitat separation, disturbance history, and reproductive ecology. The results of the study are consistent with the earlier observation that the species have remained morphologically distinct on Oland, despite evidence of sparse introgression of allozymes from weed to endemic. Disturbance is necessary not only for the creation of intermediate (hybrid) habitats but also for the establishment of the weedy parent. The transient nature of S. vulgaris populations is likely to be important in limiting introgression into S. uniflora ssp. petraea under the present disturbance regime
Chloroplast DNA haplotypes in Nordic Silene dioica: postglacial immigration from the east and the south
No full textAnalysis of PCR/RFLP variation in 57 Nordic populations of the herb Silene dioica, revealed 13 composite chloroplast DNA (cpDNA) haplotypes. The geographic distribution of the haplotypes suggests that the postglacial colonization of Fennoscandia by S. dioica may have involved immigration of populations from two main directions. The commonest cpDNA haplotype dominates in populations throughout most of Finland and northern and central Sweden, but is absent from southern Sweden. The distribution of this haplotype is interpreted in terms of immigration from an eastern or northern direction. In contrast, eight haplotypes that are absent from northern Fennoscandia are represented in populations in southern Sweden and in Denmark, suggesting colonization by populations derived from one or several refugial areas further to the south in Europe. The overall NE-SW pattern of cpDNA haplotype variation is similar to, but less diffuse than, the pattern revealed by allozyme markers
Structure of allozyme variation in Nordic Silene nutans (Caryophyllaceae): population size, geographical position and immigration history
Full text linkWe investigated allozyme variation in 34 populations of the perennial herb Silene nutans from Sweden and northern Finland, areas that were ice-covered during the last (Weichselian) glaciation. The present geographical structure of genetic variation in S. nutans in Sweden and northern Finland appears to have been mainly shaped by ancient historical processes. Patterns of variation in allele frequencies suggest two major postglacial immigration routes into Sweden, with populations entering the area from both the south and the east and forming a contact zone with admixed populations in central Sweden. While estimates of within-population genetic diversity and allelic richness are significantly correlated with present population size and geographical position (latitude), population size is not correlated with latitude. Low genetic diversity in the northern populations is more likely to have resulted from ancient stochastic events during the process of immigration than from recent population fragmentation. F-IS values are high and increase with latitude. Evidence of recent bottlenecks was detected in several southern Swedish populations: these can be interpreted in terms of population fragmentation as a result of anthropogenic disturbance. Soil pH is uncorrelated with population size and position. (C) 2004 The Linnean Society of London
Genetic variation in Scandinavian Anthericum liliago (Anthericaceae): allopolyploidy, hybridization and immigration history
No full textWe investigated patterns of isozyme variation and the hierarchic structure of genetic diversity in 25 Scandinavian populations of the lilioid herb, Anthericum liliago. Isozyme data suggest that tetraploid A. liliago has an allopolyploid origin and that A. ramosum may be one of its diploid progenitors. Two populations contained known or suspected hybrids between A. liliago and A. ramosum. Isozymes show that one population from S Sweden contains both triploid (hybrid) and tetraploid individuals whereas a putatively hybrid Danish population represents diploid A. liliago. There is an overall northward and eastward decline in allelic richness in the tetraploid populations, with the highest numbers of alleles in Denmark and SW Sweden. This pattern is consistent with a progressive loss of allelic variation during the species' postglacial colonization of Scandinavia. The between-population component of genetic diversity is 4% (compared with 12% in diploid A. ramosum), the between-region diversity component is 7% and 89% of the total diversity is stored within populations
Relationships between Nordic dogroses (Rosa L. sect. Caninae, Rosaceae) assessed by RAPDs and elliptic Fourier analysis of leaflet shape
No full textThe 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
Habitat fragmentation and the structure of genetic diversity within disjunct isolates of Anthericum ramosum L. (Anthericaceae) in Scandinavia
No full textThe lilioid herb, Anthericum ramosum, occurs in four geographically-isolated regions (Sjaelland, Skane, Oland and Gotland) in Denmark and southern Sweden. We investigated allozyme variation at nine polymorphic loci in A. ramosum from 16 sites (33 populations) in the four regions. There was no clear overall geographic pattern of differentiation between the regions, but the southernmost Gotland and the Oland populations had similar allele frequencies, suggesting that they have had a common history. the total genetic diversity (H-tot) wa 0.458 and the between-region, site- and population components of diversity accounted, respectively, for 13%, 10% and 2% of the total diversity. The species is restricted to grassland habitats. Such habitats have become increasingly rare in the Sjaelland and Skane regions, where A. ramosum now has a highly fragmented distribution. Within three of the regions (Sjaelland, Skane and Oland) there was a negative relationship between the extend of grassland habitat and the between-site components of genetic diversity. Oland, with its extensive grassland habitats and low levels of population disjunction, showed little allelic differentiation between sites and the lowest between-site component of diversity (3%), suggesting that there is (or has been) extensive gene flow between sites. The between-site components of diversity were higher within Skane (7%) and Sjaelland (12%). The high within-region G(ST) (25%) for the fourth region, Gotland, cannot be explained in terms of recent habitat disjunction but is, instead, interpreted in terms of the restricted distribution of limestone bedrock on Gotland and the fact that the southern and northern Gotland populations appear to have had different origins. (C) 2000 Linnean Society of London
Gräsmarker i allmänhet och fårsvingel i synnerhet
No full textI det fjärde numret av Essä uppmärksammas ett helt vanligt grässtrå – fårsvingeln – genom Olof Rudbeck den äldres avbildning av det i det stora botaniska verket Campus Elysii som under dramatiska omständigheter nästan brann upp i stadsbranden i Uppsala 1702. De som tittat på gräset och skrivit om det är Erik Bergqvist, Gunnar Eriksson, Honor C. Prentice, Birgitta Lillpers, Carin Franzén och Jakob Christensson
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