| 1. |
- Muyle, Aline, et al.
(författare)
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Dioecy Is Associated with High Genetic Diversity and Adaptation Rates in the Plant Genus Silene
- 2021
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Ingår i: Molecular biology and evolution. - : Oxford University Press. - 0737-4038 .- 1537-1719. ; 38:3, s. 805-818
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Tidskriftsartikel (refereegranskat)abstract
- About 15,000 angiosperm species (similar to 6%) have separate sexes, a phenomenon known as dioecy. Why dioecious taxa are so rare is still an open question. Early work reported lower species richness in dioecious compared with nondioecious sister clades, raising the hypothesis that dioecy may be an evolutionary dead-end. This hypothesis has been recently challenged by macroevolutionary analyses that detected no or even positive effect of dioecy on diversification. However, the possible genetic consequences of dioecy at the population level, which could drive the long-term fate of dioecious lineages, have not been tested so far. Here, we used a population genomics approach in the Silene genus to look for possible effects of dioecy, especially for potential evidence of evolutionary handicaps of dioecy underlying the dead-end hypothesis. We collected individual-based RNA-seq data from several populations in 13 closely related species with different sexual systems: seven dioecious, three hermaphroditic, and three gynodioecious species. We show that dioecy is associated with increased genetic diversity, as well as higher selection efficacy both against deleterious mutations and for beneficial mutations. The results hold after controlling for phylogenetic inertia, differences in species census population sizes and geographic ranges. We conclude that dioecious Silene species neither show signs of increased mutational load nor genetic evidence for extinction risk. We discuss these observations in the light of the possible demographic differences between dioecious and self-compatible hermaphroditic species and how this could be related to alternatives to the dead-end hypothesis to explain the rarity of dioecy.
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| 2. |
- Postel, Zoé, 1995-, et al.
(författare)
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Paternal leakage of plastids rescues inter-lineage hybrids in Silene nutans
- 2023
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Ingår i: Annals of Botany. - 0305-7364 .- 1095-8290.
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Tidskriftsartikel (refereegranskat)abstract
- Background and Aims Organelle genomes are usually maternally inherited in angiosperms. However, biparental inheritance has been observed, especially in hybrids resulting from crosses between divergent genetic lineages. When it concerns the plastid genome, this exceptional mode of inheritance might rescue inter-lineage hybrids suffering from plastid–nuclear incompatibilities. Genetically differentiated lineages of Silene nutans exhibit strong postzygotic isolation owing to plastid–nuclear incompatibilities, highlighted by inter-lineage hybrid chlorosis and mortality. Surviving hybrids can exhibit variegated leaves, which might indicate paternal leakage of the plastid genome. We tested whether the surviving hybrids inherited the paternal plastid genome and survived thanks to paternal leakage.Methods We characterized the leaf phenotype (fully green, variegated or white) of 504 surviving inter-lineage hybrids obtained from a reciprocal cross experiment among populations of four genetic lineages (W1, W2, W3 and E1) of S. nutans from Western Europe and genotyped 560 leaf samples (both green and white leaves for variegated hybrids) using six lineage-specific plastid single nucleotide polymorphisms.Key Results A high proportion of the surviving hybrids (≤98 %) inherited the paternal plastid genome, indicating paternal leakage. The level of paternal leakage depended on cross type and cross direction. The E1 and W2 lineages as maternal lineages led to the highest hybrid mortality and to the highest paternal leakage from W1 and W3 lineages in the few surviving hybrids. This was consistent with E1 and W2 lineages, which contained the most divergent plastid genomes. When W3 was the mother, more hybrids survived, and no paternal leakage was detected.Conclusions By providing a plastid genome potentially more compatible with the hybrid nuclear background, paternal leakage has the potential to rescue inter-lineage hybrids from plastid–nuclear incompatibilities. This phenomenon might slow down the speciation process, provided hybrid survival and reproduction can occur in the wild.
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| 3. |
- Van Rossum, Fabienne, et al.
(författare)
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The structure of allozyme variation in Silene nutans (Caryophyllaceae) in Denmark and in north-western Europe
- 2016
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Ingår i: Plant Systematics and Evolution. - : Springer Science and Business Media LLC. - 1615-6110 .- 0378-2697 .- 2199-6881. ; 302:1, s. 23-40
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Tidskriftsartikel (refereegranskat)abstract
- We used allozymes to investigate the structure of genetic variation in populations of the perennial herb Silene nutans at local (Denmark), regional (Nordic area) and wide (over a 19A degrees latitudinal gradient) geographic scales in north-western Europe. New data from Denmark were combined with data from previously studied Fennoscandian and western populations. We related patterns of nuclear variation for 26 Fennoscandian and western populations to the phylogeographic patterns revealed by four plastid (chloroplast) DNA markers. Levels of genetic diversity were similar within Denmark and Sweden/N Finland. Compared to Sweden/N Finland, the Danish populations show lower and nonsignificant F (IS) values. The genetic structure reveals no grouping of the Danish populations according to their geographic origin (Jutland-Zealand). Within Nordic populations (from Denmark, Sweden and N Finland), there is a weak geographic pattern of allozyme differentiation. The high latitude populations are genetically depauperate compared with populations from Western Europe. At the whole north-western European scale, the structure of allozyme variation within S. nutans shows geographic differentiation (Nordic versus western populations), and some congruence with plastid phylogeographic patterns. A high level of allozyme genetic differentiation is found between Nordic and western populations (8.0 %), but also between populations within haplotype categories (19.4 %). The overall geographic structure of allozyme variation of S. nutans appears to be primarily a reflection of past (postglacial) migration history, whereas more recent adaptive and stochastic processes have occurred at more local scales.
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