| 1. |
- Aaltonen, Kristina, et al.
(författare)
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Molecular Population Genetics of the SRK and SCR Self-incompatibility Genes in the Wild Plant Species Brassica cretica (Brassicaceae).
- 2009
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Ingår i: Genetics. - : Oxford University Press (OUP). - 0016-6731 .- 1943-2631. ; 181:3, s. 985-995
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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.
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| 2. |
- Aaltonen, Kristina, et al.
(författare)
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Nuclear and chloroplast microsatellites reveal extreme population differentiation and limited gene flow in the Aegean endemic Brassica cretica (Brassicaceae)
- 2007
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Ingår i: Molecular Ecology. - 0962-1083. ; 16:23, s. 4972-4983
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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.
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| 3. |
- Aaltonen, Kristina, et al.
(författare)
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The Evolution and Diversification of S-locus Haplotypes in the Brassicaceae Family.
- 2009
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Ingår i: Genetics. - : Oxford University Press (OUP). - 0016-6731 .- 1943-2631. ; 181:3, s. 977-984
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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.
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| 4. |
- Aaltonen, Kristina, et al.
(författare)
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Unequal segregation of SRK alleles at the S locus in Brassica cretica.
- 2008
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Ingår i: Genetical Research. - 1469-5073. ; 90:3, s. 223-228
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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.
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| 5. |
- Aastrup, Christian, et al.
(författare)
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Size and immune function as predictors of predation risk in nestling and newly fledged jackdaws
- 2023
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Ingår i: Animal Behaviour. - : Elsevier BV. - 0003-3472. ; 198, s. 73-84
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Tidskriftsartikel (refereegranskat)abstract
- Prey choice by predators may be based on the potential prey's condition, for example resulting in substandard individuals running a higher risk of being predated. Over 5 years, we studied young jackdaws, Corvus monedula, to determine whether size and innate baseline immune function may predict predation risk by goshawks, Accipiter gentilis, during the nestling and early fledging phases. We measured body mass, wing length, tarsus length and four innate immune indices two to four times when nestlings were 12–29 days old. To determine which individuals had been predated during the nestling phase and shortly after fledging, we searched for metal rings of the jackdaws in the only goshawk territory close to the jackdaw colony. Nestling mortality before 12 days of age was entirely due to starvation, whereas between 12 days of age and fledging, mortality was mainly due to predation. Nestlings with smaller size (mass, wing, tarsus) and low lysis titre and haptoglobin concentrations were at a higher risk of being predated before fledging. Directly after fledging, individuals with short wings were preferentially predated, with no effects of body mass, tarsus length or any of the four immune indices measured at day 29 (i.e. shortly before fledging). That lower immune function and smaller size predict predation risk in nestlings may reflect that these individuals are of poor quality and/or lag behind in development. We hypothesize that hunger makes these nestlings sit closest to the entrance hole and hence become the first to be predated. For fledglings, our results suggest that poor flight ability makes individuals with short wings the easiest targets for avian predators.
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| 6. |
- Abbott, Jessica K., et al.
(författare)
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The microevolutionary response to male-limited X-chromosome evolution in Drosophila melanogaster reflects macroevolutionary patterns
- 2020
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Ingår i: Journal of Evolutionary Biology. - : Wiley-Blackwell. - 1010-061X .- 1420-9101. ; 33:6, s. 738-750
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Tidskriftsartikel (refereegranskat)abstract
- Due to its hemizygous inheritance and role in sex determination, the X-chromosome is expected to play an important role in the evolution of sexual dimorphism and to be enriched for sexually antagonistic genetic variation. By forcing the X-chromosome to only be expressed in males over >40 generations, we changed the selection pressures on the X to become similar to those experienced by the Y. This releases the X from any constraints arising from selection in females and should lead to specialization for male fitness, which could occur either via direct effects of X-linked loci or trans-regulation of autosomal loci by the X. We found evidence of masculinization via up-regulation of male-benefit sexually antagonistic genes and down-regulation of X-linked female-benefit genes. Potential artefacts of the experimental evolution protocol are discussed and cannot be wholly discounted, leading to several caveats. Interestingly, we could detect evidence of microevolutionary changes consistent with previously documented macroevolutionary patterns, such as changes in expression consistent with previously established patterns of sexual dimorphism, an increase in the expression of metabolic genes related to mito-nuclear conflict and evidence that dosage compensation effects can be rapidly altered. These results confirm the importance of the X in the evolution of sexual dimorphism and as a source for sexually antagonistic genetic variation and demonstrate that experimental evolution can be a fruitful method for testing theories of sex chromosome evolution.
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| 7. |
- Abbott, Jessica
(författare)
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Ontogeny and Population Biology of a Sex-Limited Colour Polymorphism
- 2006
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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.
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| 8. |
- Abdi, Abdulhakim, et al.
(författare)
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Evaluating Water Controls on Vegetation Growth in the Semi-Arid Sahel Using Field and Earth Observation Data
- 2017
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Ingår i: Remote Sensing. - : MDPI AG. - 2072-4292. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Water loss is a crucial factor for vegetation in the semi-arid Sahel region of Africa. Global satellite-driven estimates of plant CO2 uptake (gross primary productivity, GPP) have been found to not accurately account for Sahelian conditions, particularly the impact of canopy water stress. Here, we identify the main biophysical limitations that induce canopy water stress in Sahelian vegetation and evaluate the relationships between field data and Earth observation-derived spectral products for up-scaling GPP. We find that plant-available water and vapor pressure deficit together control the GPP of Sahelian vegetation through their impact on the greening and browning phases. Our results show that a multiple linear regression (MLR) GPP model that combines the enhanced vegetation index, land surface temperature, and the short-wave infrared reflectance (Band 7, 2105–2155 nm) of the moderate-resolution imaging spectroradiometer satellite sensor was able to explain between 88% and 96% of the variability of eddy covariance flux tower GPP at three Sahelian sites (overall = 89%). The MLR GPP model presented here is potentially scalable at a relatively high spatial and temporal resolution. Given the scarcity of field data on CO2 fluxes in the Sahel, this scalability is important due to the low number of flux towers in the region.
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| 9. |
- Abdi, Abdulhakim M., et al.
(författare)
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Biodiversity decline with increasing crop productivity in agricultural fields revealed by satellite remote sensing
- 2021
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Ingår i: Ecological Indicators. - : Elsevier BV. - 1470-160X. ; 130
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Tidskriftsartikel (refereegranskat)abstract
- Increasing land-use intensity is a main driver of biodiversity loss in farmland, but measuring proxies for land-use intensity across entire landscapes is challenging. Here, we develop a novel method for the assessment of the impact of land-use intensity on biodiversity in agricultural landscapes using remote sensing parameters derived from the Sentinel-2 satellites. We link crop phenology and productivity parameters derived from time-series of a two-band enhanced vegetation index with biodiversity indicators (insect pollinators and insect-pollinated vascular plants) in agricultural fields in southern Sweden, with contrasting land management (i.e. conventional and organic farming). Our results show that arable land-use intensity in cereal systems dominated by spring-sown cereals can be approximated using Sentinel-2 productivity parameters. This was shown by the significant positive correlations between the amplitude and maximum value of the enhanced vegetation index on one side and farmer reported yields on the other. We also found that conventional cereal fields had 17% higher maximum and 13% higher amplitude of their enhanced vegetation index than organic fields. Sentinel-2 derived parameters were more strongly correlated with the abundance and species richness of bumblebees and the richness of vascular plants than the abundance and species richness of butterflies. The relationships we found between biodiversity and crop production proxies are consistent with predictions that increasing agricultural land-use intensity decreases field biodiversity. The newly developed method based on crop phenology and productivity parameters derived from Sentinel-2 data serves as a proof of concept for the assessment of the impact of land-use intensity on biodiversity over cereal fields across larger areas. It enables the estimation of arable productivity in cereal systems, which can then be used by ecologists and develop tools for land managers as a proxy for land-use intensity. Coupled with spatially explicit databases on agricultural land-use, this method will enable crop-specific cereal productivity estimation across large geographical regions.
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| 10. |
- Abdi, Abdulhakim M., et al.
(författare)
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Satellite Remote Sensing of Savannas: Current Status and Emerging Opportunities
- 2022
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Ingår i: Journal of Remote Sensing. - : American Association for the Advancement of Science (AAAS). - 2694-1589. ; 2022
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Tidskriftsartikel (refereegranskat)abstract
- Savannas cover a wide climatic gradient across large portions of the Earth’s land surface and are an important component of the terrestrial biosphere. Savannas have been undergoing changes that alter the composition and structure of their vegetation such as the encroachment of woody vegetation and increasing land-use intensity. Monitoring the spatial and temporal dynamics of savanna ecosystem structure (e.g., partitioning woody and herbaceous vegetation) and function (e.g., aboveground biomass) is of high importance. Major challenges include misclassification of savannas as forests at the mesic end of their range, disentangling the contribution of woody and herbaceous vegetation to aboveground biomass, and quantifying and mapping fuel loads. Here, we review current (2010–present) research in the application of satellite remote sensing in savannas at regional and global scales. We identify emerging opportunities in satellite remote sensing that can help overcome existing challenges. We provide recommendations on how these opportunities can be leveraged, specifically (1) the development of a conceptual framework that leads to a consistent definition of savannas in remote sensing; (2) improving mapping of savannas to include ecologically relevant information such as soil properties and fire activity; (3) exploiting high-resolution imagery provided by nanosatellites to better understand the role of landscape structure in ecosystem functioning; and (4) using novel approaches from artificial intelligence and machine learning in combination with multisource satellite observations, e.g., multi-/hyperspectral, synthetic aperture radar (SAR), and light detection and ranging (lidar), and data on plant traits to infer potentially new relationships between biotic and abiotic components of savannas that can be either proven or disproven with targeted field experiments.
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