| 1. |
- Aaltonen, Kristina, et al.
(författare)
-
Molecular Population Genetics of the SRK and SCR Self-incompatibility Genes in the Wild Plant Species Brassica cretica (Brassicaceae).
- 2009
-
Ingår i: Genetics. - : Oxford University Press (OUP). - 0016-6731 .- 1943-2631. ; 181:3, s. 985-995
-
Tidskriftsartikel (refereegranskat)abstract
- Self-incompatibility (SI) in plants is a classic example of a trait evolving under strong frequency-dependent selection. As a consequence, population genetic theory predicts that the S locus, which controls SI, should maintain numerous alleles, display a high level of nucleotide diversity, and, in structured populations, show a lower level of among-population differentiation compared to neutral loci. Population-level investigations of DNA sequence variation at the S locus have recently been carried out in the genus Arabidopsis, largely confirming results from theoretical models of S-locus evolutionary dynamics, but no comparable studies have been done in wild Brassica species. In this study, we sequenced parts of the S-locus genes SRK and SCR, two tightly linked genes that are directly involved in the determination of SI specificity, in samples from four natural populations of the wild species Brassica cretica. The amount and distribution of nucleotide diversity, as well as the frequency spectrum of putative functional haplotypes, observed at the S locus in B. cretica fit very well with expectations from theoretical models, providing strong evidence for frequency-dependent selection acting on the S locus in a wild Brassica species.
|
|
| 2. |
- Aaltonen, Kristina, et al.
(författare)
-
Nuclear and chloroplast microsatellites reveal extreme population differentiation and limited gene flow in the Aegean endemic Brassica cretica (Brassicaceae)
- 2007
-
Ingår i: Molecular Ecology. - 0962-1083. ; 16:23, s. 4972-4983
-
Tidskriftsartikel (refereegranskat)abstract
- Nuclear and chloroplast microsatellite markers were used to study population structure and gene flow among seven Cretan populations of the Aegean endemic plant species Brassica cretica (Brassicaceae). Both nuclear and chloroplast markers revealed exceptionally high levels of population differentiation (overall FST = 0.628 and 1.000, respectively) and relatively little within-population diversity (overall HS = 0.211 and 0.000, respectively). Maximum-likelihood estimates of directional migration rates were low among all pairs of populations (average Nm = 0.286). There was no evidence that differences in flower colour between populations had any influence on historical levels of gene flow. In addition, a haplotype network showed that all five chloroplast haplotypes found in the sample were closely related. Together, these results suggest that current patterns of diversification in B. cretica are mainly a result of genetic drift during the last half million years. The main conclusions from the present study are consistent with the prevailing hypothesis that plant diversification in the Aegean region is driven by random rather than adaptive differentiation among isolated populations.
|
|
| 3. |
- Aaltonen, Kristina, et al.
(författare)
-
The Evolution and Diversification of S-locus Haplotypes in the Brassicaceae Family.
- 2009
-
Ingår i: Genetics. - : Oxford University Press (OUP). - 0016-6731 .- 1943-2631. ; 181:3, s. 977-984
-
Tidskriftsartikel (refereegranskat)abstract
- Self-incompatibility (SI) in the Brassicaceae plant family is controlled by the SRK and SCR genes situated at the S locus. A large number of S haplotypes have been identified, mainly in cultivated species of the Brassica and Raphanus genera, but recently also in wild Arabidopsis species. Here, we used DNA sequences from the SRK and SCR genes of the wild Brassica species B. cretica, together with publicly available sequence data from other Brassicaceae species, to investigate the evolutionary relationships between S haplotypes in the Brassicaceae family. The results reveal that wild and cultivated Brassica species have similar levels of SRK diversity indicating that domestication has had but a minor effect on S-locus diversity in Brassica. Our results also show that a common set of S haplotypes were present in the ancestor of the Brassica and Arabidopsis genera, that only a small number of haplotypes survived in the Brassica lineage after its separation from Arabidopsis, and that diversification within the two Brassica dominance classes occurred after the split between the two lineages. We also find indications that recombination may have occurred between the kinase domain of SRK and the SCR gene in Brassica.
|
|
| 4. |
- Aaltonen, Kristina, et al.
(författare)
-
Unequal segregation of SRK alleles at the S locus in Brassica cretica.
- 2008
-
Ingår i: Genetical Research. - 1469-5073. ; 90:3, s. 223-228
-
Tidskriftsartikel (refereegranskat)abstract
- In the Brassicaceae plant family, which includes the Arabidopsis and Brassica genera, self-incompatibility (SI) is controlled by genes at the S locus. Using experimental crosses, we studied the pattern of inheritance of S-locus alleles in the wild species Brassica cretica. Four full-sib families were established and unequal segregation of alleles at the SRK SI gene was found in one family. The segregation distortion acted in favour of a recessive (class II) allele and was best explained by some form of gametic-level selection. Our findings are discussed in the light of theoretical predictions of differential accumulation of deleterious mutations among S-locus alleles.
|
|
| 5. |
- Abbott, Jessica
(författare)
-
Ontogeny and Population Biology of a Sex-Limited Colour Polymorphism
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study has involved investigation of number of populations of the damselfly Ischnura elegans over several years, looking at frequency changes over time, morphological differences between the sexes and the morphs, differences in growth rate and development time, differences in fecundity between the morphs, and genetic differentiation between populations. I. elegans is a small annual damselfly with three female colour morphs (Androchrome, Infuscans, and Infuscans-obsoleta), one of which (the Androchrome) is considered a male mimic; males are monomorphic. Empirically estimated selection coefficients were used in a population genetic and dynamic model with environmental variation which predicted coexistence of the three morphs. This suggests that negative frequency-dependence on fecundity mediated by male mating harassment is sufficient to explain coexistence of the morphs. Field data also showed that fecundity decreased with increasing frequency in the population for all three morphs. Investigation of sexual dimorphism revealed that the sexes differed in development time, growth rates, and adult size and shape and that sexual size dimorphism is produced in I. elegans by a combination of development time and development rate acting in concert. The female morphs also differed in development time, growth rates, and adult size and shape, although in this case effects of development time and development rate cancelled each other out. In addition, male-like body shape had a negative effect on fecundity in Infuscans-obsoleta females but not in Androchrome or Infuscans females. Quantitative genetic parameters for morphological traits showed that an evolutionary response to selection on body shape is possible. Comparisons of Fst-values and the lack of isolation by distance both suggest that this is a highly dynamic non-equilibrium system, and genetic diversity appears to be influenced by wind direction. The results in this study indicate that the morphs are subject to negative frequency-dependent selection via male mating harassment, and that the differences between the morphs are part of their identity as alternative adaptive strategies.
|
|
| 6. |
- Abraham, David
(författare)
-
Molecular aspects of pheromone evolution in moths
- 2002
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Moths rely on the sense of smell (olfaction) as the main sensory input system in search for potential food sources and in selection of suitable females by males. Specific pheromones are fundamental to the reproductive isolation of species and consequently the olfactory system of moths has evolved to a high level of sensitivity and specificity. This thesis investigates differences between two pheromone types found in geometrid and noctuid moths. These two pheromone types are based on olefinic acetate and polyenic hydrocarbon pheromone components that differ in biosynthesis. Olefinic acetates are biosynthesised from palmitic acid while the polyenic hydrocarbon pheromone components are biosynthesised from linoleic or linolenic acid. To examine the evolution of these pheromone types within the geometrid moth family I constructed a phylogenetic tree based on 'neutral' genes. The combination of the phylogenetic tree with current knowledge about the two pheromone types, revealed that subfamilies within the geometrids have changed at least twice from one pheromone type to another. In addition, I examined if species that use different pheromone components also differ in their pheromone binding proteins (PBPs). Pheromone-binding proteins are soluble proteins, which increase the capture and the solubilization of pheromone molecules in the lymph surrounding the olfactory receptors. PBPs have been identified for several species of moths, among which also noctuid species. The Noctuid PBPs that identified so far, are divided into two groups, a conserved and a more variable group. These different PBP groups originate from gene duplication; the genes encoding PBPs in Agrotis ipsilon and Agrotis segetum all comprise three exons and two introns but differ in length, mostly in intron 2. It has been hypothesised that the differences between PBPs from the two groups and between PBPs from different species were related to their pheromone system. Species using the same main pheromone components could have similar PBPs. Phylogenetic analysis of all known PBPs supported this hypothesis for the noctuid PBPs that use olefinic acetate pheromone components. For this reason, I therefore attempted to identify PBPs for the geometrids Idaea aversata and Bupalus piniaria, and the closely related drepanid Cilix glaucata, which represent both the olefinic acetate and the polyenic hydrocarbon pheromone types. From partial sequences I found that these PBPs belong to the non-noctuid group of PBPs that show high similarity when the species are closely related, regardless of the pheromone types they represent.
|
|
| 7. |
- Abrahamsson, M. L. A., et al.
(författare)
-
Ruthenium-manganese complexes for artificial photosynthesis : Factors controlling intramolecular electron transfer and excited-state quenching reactions
- 2002
-
Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 41:6, s. 1534-1544
-
Tidskriftsartikel (refereegranskat)abstract
- Continuing our work toward a system mimicking the electron-transfer steps from manganese to P-680(+) in photosystem II (PS II), we report a series of ruthenium(II)-manganese(II) complexes that display intramolecular electron transfer from manganese(II) to photooxidized ruthenium(III). The electron-transfer rate constant (k(ET)) values span a large range, 1 X 10(5)-2 x 10(7) s(-1), and we have investigated different factors that are responsible for the variation. The reorganization energies determined experimentally (lambda = 1.5-2.0 eV) are larger than expected for solvent reorganization in complexes of similar size in polar solvents (typically lambda approximate to 1.0 eV). This result indicates that the inner reorganization energy is relatively large and, consequently, that at moderate driving force values manganese complexes are not fast donors. Both the type of manganese ligand and the link between the two metals are shown to be of great importance to the electron-transfer rate. In contrast, we show that the quenching of the excited state of the ruthenium(II) moiety by manganese(II) in this series of complexes mainly depends on the distance between the metals. However, by synthetically modifying the sensitizer so that the lowest metal-to-ligand charge transfer state was localized on the nonbridging ruthenium(II) ligands, we could reduce the quenching rate constant in one complex by a factor of 700 without changing the bridging ligand. Still, the manganese(II)-ruthenium (III) electrontransfer rate constant was not reduced. Consequently, the modification resulted in a complex with very favorable properties.
|
|
| 8. |
- Abreu, Paulo Cesar, et al.
(författare)
-
Importance of biofilm as food source for shrimps (Farafantepenaeus paulensis) evaluated by stable isotopes (∂13C and ∂15N)
- 2007
-
Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 347:1-2, s. 88-96
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract The contribution of biofilm and artificial feeds for the growth of the pink shrimp Farfantepenaeus paulensis reared in tanks and net cages were evaluated by using stable isotope (δ13C and δ15N) analysis. In the net cage experiment, mass balance and mixing equations showed that the biofilm contribution to shrimp growth was over 49% of carbon and 70% of nitrogen. These data suggest that the artificial feed offered in this experiment, although ingested, was not properly incorporated in the shrimp tissue. In contrast, biofilm growing in tanks contributed little to the nitrogen incorporated by the shrimp (maximum of 29%). In this experiment, shrimp presented an unusually large isotope fractionation. These results imply that the shrimp are selectively ingesting some items from the biofilm, or differentially assimilate specific items of the artificial feed, due to differential digestibility. The hypothesis of selective feeding of biofilm microorganisms was corroborated in the experiment with net cages, where shrimp preferentially consumed centric diatoms. This study also demonstrated that shrimp biofilm consumption and the presence of artificial feed largely influenced biofilm formation. The consumption of centric diatoms by shrimp seem to stimulate biofilm chlorophyll-a, while biofilm δ15N values measured in tanks indicate that microorganisms present in the biofilm absorbs nitrogen released by artificial feed after its decomposition.
|
|
| 9. |
- Abreu, PC, et al.
(författare)
-
Eutrophication processes and trophic interactions in a shallow estuary: Preliminary results based on stable isotope analysis (delta C-13 and delta N-15)
- 2006
-
Ingår i: Estuaries and Coasts. - 1559-2731. ; 29:2, s. 277-285
-
Tidskriftsartikel (refereegranskat)abstract
- Stable isotopes ratios (delta C-13 and delta N-15) were measured in primary producers and consumers of two bays with contrasting eutrophic conditions in the pains Lagoon estuary, southern Brazil: the Justino bay, a more pristine ecosystem, and the Mangueira bay, a heavily polluted region that receives the Rio Grande city sewage and effluents of several industries. delta C-13 values of organisms collected in both subsystems were not different, but delta N-15 values had significant statistical differences, ca. 3.5 parts per thousand higher in the Mangueira bay. It is likely that primary producers and consumers in this subsystem are greatly influenced by higher nitrogen input due to domestic and industrial sewages. The stable isotope analysis also corroborated several trophic interactions previously established by gut content analysis, and due to its higher sensitivity, it was possible to better determine the contributions of different primary producers and detrital fractions to the consumers' diets. It was confirmed that plant detritus represents the main food source for most organisms. The stable isotope analysis also demonstrated that detritivorous benthic organisms in the same habitat have distinct diet compositions, with differential consumption of C3 and C4 plants. This technique showed that some consumers that eat detritus do not have in their stable isotopic signature any relationship with that of plants. It is likely that these consumers assimilate their carbon and nitrogen from other sources like microalgae or microorganisms that colonize decaying plants.
|
|
| 10. |
- Ackefors, Hans
(författare)
-
Global fisheries - threats and opportunities
- 2009
-
Ingår i: Fisheries, sustainablity and development. - Stockholm : Kungl. Skogs- och lantbruksakademien. ; , s. 35-68-
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
|
|
