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- Alström-Rapaport, Cecilia, et al.
(författare)
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Seasonal variation in the mode of reproduction of Ulva intestinalis in a brackish water environment
- 2010
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Ingår i: Aquatic Botany. - : Elsevier BV. - 0304-3770 .- 1879-1522. ; 93:4, s. 244-249
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Tidskriftsartikel (refereegranskat)abstract
- We explored the reproductive modes of Viva intestinalis in the inner part of the Baltic Sea during three consecutive years by using five microsatellite loci to estimate the relative abundance of diploid sporophytes and haploid gametophytes. Our results suggest that both diploid sporophytes and haploid gametophytes occur regularly in the Baltic Sea. The ratio of haploid to diploid individuals changes with seasons. Sporophytes are more abundant than gametophytes throughout the year, but the proportion of haploids increases from 10% in early summer to 35% in September. The over-wintering takes primarily place as diploid spores released by sporophytes. The sporophytes appear to reproduce both sexually and asexually in the Baltic Sea, since clones were found for this life phase. The fraction of individuals which belonged to an apparent diploid clone was higher in spring (62%) than in autumn (33%). We also found evidence for asexual clones in haploid gametophytes. The presence of both diploid and haploid individuals and the pattern of genetic and genotypic diversity provide evidence of sexual reproduction in the Baltic Sea. Thus the sporophytes and gametophytes do not function as two reproductively separate units. Compared with many other algal species with a reduced reproductive cycle in low salinity, U. intestinalis differs by having a multitude of reproductive modes also in the brackish water Baltic Sea, which can in part explain the dynamic propagation and high adaptability of the species.
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- Andersson, Anna-Carin, 1970-
(författare)
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Postglacial Population History of the Common Shrew (Sorex araneus) in Fennoscandia : Molekylära studier av återkolonisation, könsbundet genflöde och kromosomrasbildning.
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The common shrew, Sorex araneus, has one of the most variable karyotypes among mammals, displaying numerous chromosomes races throughout its distribution, which can be categorized into different karyotypic groups. The objective of this thesis was to examine the postglacial population history of Fennoscandian common shrews using autosomal microsatellites, mitochondrial DNA (mtDNA) and a Y chromosome specific microsatellite (L8Y).Autosomal microsatellites and mtDNA revealed weak genetic structure over a hybrid zone between the karyotypically divergent Northern and Western karyotypic groups. However, the genetic structure displayed by the Y chromosome microsatellite was orders of magnitude higher. Hence, considerable chromosomal differences between the groups do not prevent female gene flow, while male gene flow is reduced (cf. Haldane's rule). Further, the results suggest that the Haldane effect may be caused by the chromosomal differences between the karyotypic groups.No mtDNA differentiation was observed either between chromosome races or between the Northern and Western karyotypic groups in Fennoscandia. The combined pattern of karyotypic and mtDNA variation of Fennoscandian common shrews, suggest bi-directional postglacial recolonisation from a single refugium in Europe. The variation of the Y-linked microsatellite supported this conclusion. In contrast, significant mtDNA structure, discordant with the karyotypic variation, revealed that common shrews in southern Finland belong to a different lineage than remaining Fennoscandian regions, implying postglacial recolonisation from a different source.MtDNA variation of the chromosome races in Sweden supports the hypothesis that three races of the Western karyotypic group have been formed through whole arm reciprocal translocations (WARTs), as suggested by their mutual karyotypic variation. The variation of the molecular markers supports the theory of rapid karyotypic evolution in the common shrew.
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- Lundqvist, Anna-Carin, et al.
(författare)
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Fennoscandian phylogeography of the common shrew Sorex araneus. Postglacial recolonisation-combining information from chromosomal variation with mitochondrial DNA data
- 2011
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Ingår i: Acta Theriologica. - : Springer Science and Business Media LLC. - 0001-7051 .- 2190-3743. ; 56:2, s. 103-116
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Tidskriftsartikel (refereegranskat)abstract
- We examine mtDNA variation of the common shrew in Fennoscandia to explore the incongruence found in previous studies using chromosomal and mitochondrial markers, aiming to reveal post-glacial recolonisation patterns. A total of 241 common shrews from 51 localities in Fennoscandia were analysed. This area includes a secondary contact zone between two groups (the Northern group and the Western group) showing distinct karyotypes. All individuals were sequenced for 447 bp of the mitochondrial control region. No significant differentiation in the mtDNA variation was observed between the two major chromosomal groups in Fennoscandia. The star-like shape of the sequence network for the entire study area shows the most common haplotype A as ancestral in all regions but one, in situ formation of most haplotypes and population expansion. The only significant mtDNA structure observed occurs between south Finland and the rest of Fennoscandia. We propose that the Northern and Western group shared a common refugium during the Last Glacial Maximum but recolonised Fennoscandia via two routes. Karyotypic differences between south and north Finland has led researchers to suggest that both regions originate from the same ancestral population east of Finland. The observed divergence of mtDNA variation between these two regions supports this hypothesis.
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