| 1. |
- Backström, Niclas, et al.
(författare)
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The recombination landscape of the zebra finch Taeniopygia guttata genome
- 2010
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Ingår i: Genome Research. - : Cold Spring Harbor Laboratory. - 1088-9051 .- 1549-5469. ; 20:4, s. 485-495
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the causes and consequences of variation in the rate of recombination is essential since this parameter is considered to affect levels of genetic variability, the efficacy of selection, and the design of association and linkage mapping studies. However, there is limited knowledge about the factors governing recombination rate variation. We genotyped 1920 single nucleotide polymorphisms in a multigeneration pedigree of more than 1000 zebra finches (Taeniopygia guttata) to develop a genetic linkage map, and then we used these map data together with the recently available draft genome sequence of the zebra finch to estimate recombination rates in 1 Mb intervals across the genome. The average zebra finch recombination rate (1.5 cM/Mb) is higher than in humans, but significantly lower than in chicken. The local rates of recombination in chicken and zebra finch were only weakly correlated, demonstrating evolutionary turnover of the recombination landscape in birds. The distribution of recombination events was heavily biased toward ends of chromosomes, with a stronger telomere effect than so far seen in any organism. In fact, the recombination rate was as low as 0.1 cM/Mb in intervals up to 100 Mb long in the middle of the larger chromosomes. We found a positive correlation between recombination rate and GC content, as well as GC-rich sequence motifs. Levels of linkage disequilibrium (LD) were significantly higher in regions of low recombination, showing that heterogeneity in recombination rates have left a footprint on the genomic landscape of LD in zebra finch populations.
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| 2. |
- Bolund, Elisabeth, et al.
(författare)
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Correlates of male fitness in captive zebra finches : a comparison of methods to disentangle genetic and environmental effects
- 2011
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Ingår i: BMC Evolutionary Biology. - : Springer Science and Business Media LLC. - 1471-2148. ; 11, s. 327-
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Tidskriftsartikel (refereegranskat)abstract
- Backgound: It is a common observation in evolutionary studies that larger, more ornamented or earlier breeding individuals have higher fitness, but that body size, ornamentation or breeding time does not change despite of sometimes substantial heritability for these traits. A possible explanation for this is that these traits do not causally affect fitness, but rather happen to be indirectly correlated with fitness via unmeasured non-heritable aspects of condition (e. g. undernourished offspring grow small and have low fitness as adults due to poor health). Whether this explanation applies to a specific case can be examined by decomposing the covariance between trait and fitness into its genetic and environmental components using pedigree-based animal models. We here examine different methods of doing this for a captive zebra finch population where male fitness was measured in communal aviaries in relation to three phenotypic traits (tarsus length, beak colour and song rate). Results: Our case study illustrates how methods that regress fitness over breeding values for phenotypic traits yield biased estimates as well as anti-conservative standard errors. Hence, it is necessary to estimate the genetic and environmental covariances between trait and fitness directly from a bivariate model. This method, however, is very demanding in terms of sample sizes. In our study parameter estimates of selection gradients for tarsus were consistent with the hypothesis of environmentally induced bias (beta(A) = 0.035 +/- 0.25 (SE), beta(E) = 0.57 +/- 0.28 (SE)), yet this differences between genetic and environmental selection gradients falls short of statistical significance. Conclusions: To examine the generality of the idea that phenotypic selection gradients for certain traits (like size) are consistently upwardly biased by environmental covariance a meta-analysis across study systems will be needed.
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| 3. |
- Borodin, Pavel, et al.
(författare)
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Mendelian nightmares : the germline-restricted chromosome of songbirds
- 2022
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Ingår i: Chromosome Research. - : Springer Nature. - 0967-3849 .- 1573-6849. ; 30:2-3, s. 255-272
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Forskningsöversikt (refereegranskat)abstract
- Germline-restricted chromosomes (GRCs) are accessory chromosomes that occur only in germ cells. They are eliminated from somatic cells through programmed DNA elimination during embryo development. GRCs have been observed in several unrelated animal taxa and show peculiar modes of non-Mendelian inheritance and within-individual elimination. Recent cytogenetic and phylogenomic evidence suggests that a GRC is present across the species-rich songbirds, but absent in non-passerine birds, implying that over half of all 10,500 bird species have extensive germline/soma genome differences. Here, we review recent insights gained from genomic, transcriptomic, and cytogenetic approaches with regard to the genetic content, phylogenetic distribution, and inheritance of the songbird GRC. While many questions remain unsolved in terms of GRC inheritance, elimination, and function, we discuss plausible scenarios and future directions for understanding this widespread form of programmed DNA elimination.
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| 4. |
- Evans, Simon R., et al.
(författare)
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Nonautosomal Genetic Variation in Carotenoid Coloration
- 2014
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 184:3, s. 374-383
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Tidskriftsartikel (refereegranskat)abstract
- Carotenoid-based coloration plays an important role in signaling, is often sexually dimorphic, and is potentially subject to directional and/or sex-specific selection. To understand the evolutionary dynamics of such color traits, it is essential to quantify patterns of inheritance, yet nonautosomal sources of genetic variation are easily overlooked by classical heritability analyses. Carotenoid metabolism has recently been linked to mitochondria, highlighting the potential for color variation to be explained by cytoplasmically inherited factors. In this study, we used quantitative genetic animal models to estimate the importance of mitochondrial and sex chromosome-linked sources of genetic variation in coloration in two songbird populations in which dietary carotenoids are either unmodified (great tit plumage) or metabolized into alternative color forms (zebra finch beak). We found no significant Z-linked genetic variance in great tit plumage coloration, while zebra finch beak coloration exhibited significant W linkage and cytoplasmic inheritance. Our results support cytoplasmic inheritance of color in the zebra finch, a trait based on endogenously metabolized carotenoids, and demonstrate the potential for nonautosomal sources to account for a considerable share of genetic variation in coloration. Although often overlooked, such nonautosomal genetic variation exhibits sex-dependent patterns of inheritance and potentially influences the evolution of sexual dichromatism.
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| 5. |
- Forstmeier, Wolfgang, et al.
(författare)
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Heterozygosity-fitness correlations in zebra finches : microsatellite markers can be better than their reputation
- 2012
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 21:13, s. 3237-3249
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Tidskriftsartikel (refereegranskat)abstract
- Numerous studies have reported associations between heterozygosity in microsatellite markers and fitness-related traits (heterozygosityfitness correlations, HFCs). However, it has often been questioned whether HFCs reflect general inbreeding depression, because a small panel of microsatellite markers does not reflect very well an individuals inbreeding coefficient (F) as calculated from a pedigree. Here, we challenge this prevailing view. Because of chance events during Mendelian segregation, an individuals realized proportion of the genome that is identical by descent (IBD) may substantially deviate from the pedigree-based expectation (i.e. F). This Mendelian noise may result in a weak correlation between F and multi-locus heterozygosity, but this does not imply that multi-locus heterozygosity is a bad estimator of realized IBD. We examined correlations between 11 fitness-related traits measured in up to 1192 captive zebra finches and three measures of inbreeding: (i) heterozygosity across 11 microsatellite markers, (ii) heterozygosity across 1359 single-nucleotide polymorphism (SNP) markers and (iii) F, based on a 5th-generation pedigree. All 11 phenotypic traits showed positive relationships with measures of heterozygosity, especially traits that are most closely related to fitness. Remarkably, the small panel of microsatellite markers produced equally strong HFCs as the large panel of SNP markers. Both marker-based approaches produced stronger correlations with phenotypes than the pedigree-based F, and this did not seem to result from the shortness of our pedigree. We argue that a small panel of microsatellites with high allelic richness may better reflect an individuals realized IBD than previously appreciated, especially in species like the zebra finch, where much of the genome is inherited in large blocks that rarely experience cross-over during meiosis.
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| 6. |
- Forstmeier, Wolfgang, et al.
(författare)
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Trisomy and triploidy are sources of embryo mortality in the zebra finch
- 2010
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 277:1694, s. 2655-2660
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Tidskriftsartikel (refereegranskat)abstract
- Hatching failure is a surprisingly common phenomenon given that natural selection constantly works against it. In birds, an average of about 10 per cent of eggs across species fail to hatch, often owing to the death of embryos. While embryo mortality owing to inbreeding is both well-documented and evolutionarily plausible, this is not true for other sources of mortality. In fact, the basis for hatching failure in natural populations remains largely unexplained. Here, we demonstrate that embryo mortality in captive zebra finches (Taeniopygia guttata) follows from chromosomal aneuploidy or polyploidy. As part of microsatellite genotyping of a captive breeding population, we found 12 individuals ( 3.6%) with three alleles among 331 embryos that had died during development, while there were no such cases observed among 1210 adult birds. Subsequent genotyping of 1920 single nucleotide polymorphism markers distributed across the genome in birds with three alleles at microsatellite loci, and in greater than 1000 normal birds, revealed that the aberrant karyotypes involved cases of both trisomies and triploidy. Cases of both maternally and paternally inherited trisomies resulted from non-disjunction during meiosis. Maternally inherited cases of triploidy were attributable to failure of meiosis leading to diploid eggs, while paternally inherited triploidy could have arisen either from diploid sperm or from dispermy. Our initial microsatellite screening set only had the power to detect less than 10 per cent of trisomies and by extrapolation, our data therefore tentatively suggest that trisomy might be a major cause of embryo mortality in zebra finches.
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| 7. |
- Griffith, Simon C., et al.
(författare)
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Variation in reproductive success across captive populations: Methodological differences, potential biases and opportunities
- 2017
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Ingår i: Ethology. - : Wiley. - 1439-0310 .- 0179-1613. ; 123:1, s. 1-29
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Tidskriftsartikel (refereegranskat)abstract
- Our understanding of fundamental organismal biology has been disproportionately influenced by studies of a relatively small number of ‘model’ species extensively studied in captivity. Laboratory populations of model species are commonly subject to a number of forms of past and current selection that may affect experimental outcomes. Here, we examine these processes and their outcomes in one of the most widely used vertebrate species in the laboratory – the zebra finch (Taeniopygia guttata). This important model species is used for research across a broad range of fields, partly due to the ease with which it can be bred in captivity. However despite this perceived amenability, we demonstrate extensive variation in the success with which different laboratories and studies bred their subjects, and overall only 64% of all females that were given the opportunity, bred successfully in the laboratory. We identify and review several environmental, husbandry, life-history and behavioural factors that potentially contribute to this variation. The variation in reproductive success across individuals could lead to biases in experimental outcomes and drive some of the heterogeneity in research outcomes across studies. The zebra finch remains an excellent captive animal system and our aim is to sharpen the insight that future studies of this species can provide, both to our understanding of this species and also with respect to the reproduction of captive animals more widely. We hope to improve systematic reporting methods and that further investigation of the issues we raise will lead both to advances in our fundamental understanding of avian reproduction as well as to improvements in future welfare and experimental efficiency.
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| 8. |
- Husby, Arild, et al.
(författare)
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Sex chromosome linked genetic variance and the evolution of sexual dimorphism of quantitative traits
- 2013
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 67:3, s. 609-619
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Tidskriftsartikel (refereegranskat)abstract
- Theory predicts that sex chromsome linkage should reduce intersexual genetic correlations thereby allowing the evolution of sexual dimorphism. Empirical evidence for sex linkage has come largely from crosses and few studies have examined how sexual dimorphism and sex linkage are related within outbred populations. Here, we use data on an array of different traits measured on over 10,000 individuals from two pedigreed populations of birds (collared flycatcher and zebra finch) to estimate the amount of sex-linked genetic variance (h2z). Of 17 traits examined, eight showed a nonzero h2Z estimate but only four were significantly different from zero (wing patch size and tarsus length in collared flycatchers, wing length and beak color in zebra finches). We further tested how sexual dimorphism and the mode of selection operating on the trait relate to the proportion of sex-linked genetic variance. Sexually selected traits did not show higher h2Z than morphological traits and there was only a weak positive relationship between h2Z and sexual dimorphism. However, given the relative scarcity of empirical studies, it is premature to make conclusions about the role of sex chromosome linkage in the evolution of sexual dimorphism.
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| 9. |
- Kinsella, Cormac M., et al.
(författare)
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Programmed DNA elimination of germline development genes in songbirds
- 2019
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Ingår i: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- In some eukaryotes, germline and somatic genomes differ dramatically in their composition. Here we characterise a major germline-soma dissimilarity caused by a germline-restricted chromosome (GRC) in songbirds. We show that the zebra finch GRC contains >115 genes paralogous to single-copy genes on 18 autosomes and the Z chromosome, and is enriched in genes involved in female gonad development. Many genes are likely functional, evidenced by expression in testes and ovaries at the RNA and protein level. Using comparative genomics, we show that genes have been added to the GRC over millions of years of evolution, with embryonic development genes bicc1 and trim71 dating to the ancestor of songbirds and dozens of other genes added very recently. The somatic elimination of this evolutionarily dynamic chromosome in songbirds implies a unique mechanism to minimise genetic conflict between germline and soma, relevant to antagonistic pleiotropy, an evolutionary process underlying ageing and sexual traits.
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| 10. |
- Kleineidam, Luca, et al.
(författare)
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Midlife occupational cognitive requirements protect cognitive function in old age by increasing cognitive reserve
- 2022
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Ingår i: Frontiers in Psychology. - : Frontiers Media SA. - 1664-1078. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Several lifestyle factors promote protection against Alzheimer's disease (AD) throughout a person's lifespan. Although such protective effects have been described for occupational cognitive requirements (OCR) in midlife, it is currently unknown whether they are conveyed by brain maintenance (BM), brain reserve (BR), or cognitive reserve (CR) or a combination of them. Methods: We systematically derived hypotheses for these resilience concepts and tested them in the population-based AgeCoDe cohort and memory clinic-based AD high-risk DELCODE study. The OCR score (OCRS) was measured using job activities based on the O*NET occupational classification system. Four sets of analyses were conducted: (1) the interaction of OCR and APOE-ε4 with regard to cognitive decline (N = 2,369, AgeCoDe), (2) association with differentially shaped retrospective trajectories before the onset of dementia of the Alzheimer's type (DAT; N = 474, AgeCoDe), (3) cross-sectional interaction of the OCR and cerebrospinal fluid (CSF) AD biomarkers and brain structural measures regarding memory function (N = 873, DELCODE), and (4) cross-sectional and longitudinal association of OCR with CSF AD biomarkers and brain structural measures (N = 873, DELCODE). Results: Regarding (1), higher OCRS was associated with a reduced association of APOE-ε4 with cognitive decline (mean follow-up = 6.03 years), consistent with CR and BR. Regarding (2), high OCRS was associated with a later onset but subsequently stronger cognitive decline in individuals converting to DAT, consistent with CR. Regarding (3), higher OCRS was associated with a weaker association of the CSF Aβ42/40 ratio and hippocampal volume with memory function, consistent with CR. Regarding (4), OCR was not associated with the levels or changes in CSF AD biomarkers (mean follow-up = 2.61 years). We found a cross-sectional, age-independent association of OCRS with some MRI markers, but no association with 1-year-change. OCR was not associated with the intracranial volume. These results are not completely consistent with those of BR or BM. Discussion: Our results support the link between OCR and CR. Promoting and seeking complex and stimulating work conditions in midlife could therefore contribute to increased resistance to pathologies in old age and might complement prevention measures aimed at reducing pathology.
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| 11. |
- Knief, Ulrich, et al.
(författare)
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A prezygotic transmission distorter acting equally in female and male zebra finches Taeniopygia guttata
- 2015
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 24:15, s. 3846-3859
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Tidskriftsartikel (refereegranskat)abstract
- The two parental alleles at a specific locus are usually inherited with equal probability to the offspring. However, at least three processes can lead to an apparent departure from fair segregation: early viability selection, biased gene conversion and various kinds of segregation distortion. Here, we conduct a genome-wide scan for transmission distortion in a captive population of zebra finches (Taeniopygia guttata) using 1302 single-nucleotide polymorphisms (SNPs) followed by confirmatory analyses on independent samples from the same population. In the initial genome-wide scan, we found significant distortion at three linked loci on chromosome Tgu2 and we were able to replicate this finding in each of two follow-up data sets [overall transmission ratio=0.567 (95% CI=0.536-0.600), based on 1101 informative meioses]. Although the driving allele was preferentially transmitted by both heterozygous females [ratio=0.560 (95% CI=0.519-0.603)] and heterozygous males [ratio=0.575 (95% CI=0.531-0.623)], we could rule out postzygotic viability selection and biased gene conversion as possible mechanisms. Early postzygotic viability selection is unlikely, because it would result in eggs with no visible embryo and hence no opportunity for genotyping, and we confirmed that both females and males heterozygous for the driving allele did not produce a larger proportion of such eggs than homozygous birds. Biased gene conversion is expected to be rather localized, while we could trace transmission distortion in haplotypes of several megabases in a recombination desert. Thus, we here report the rare case of a prezygotically active transmission distorter operating equally effectively in female and male meioses.
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| 12. |
- Knief, Ulrich, et al.
(författare)
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Association mapping of morphological traits in wild and captive zebra finches : reliable within, but not between populations
- 2017
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 26:5, s. 1285-1305
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Tidskriftsartikel (refereegranskat)abstract
- Identifying causal genetic variants underlying heritable phenotypic variation is a long-standing goal in evolutionary genetics. We previously identified several quantitative trait loci (QTL) for five morphological traits in a captive population of zebra finches (Taeniopygia guttata) by whole-genome linkage mapping. We here follow up on these studies with the aim to narrow down on the quantitative trait variants (QTN) in one wild and three captive populations. First, we performed an association study using 672 single nucleotide polymorphisms (SNPs) within candidate genes located in the previously identified QTL regions in a sample of 939 wild-caught zebra finches. Then, we validated the most promising SNP-phenotype associations (n=25 SNPs) in 5228 birds from four populations. Genotype-phenotype associations were generally weak in the wild population, where linkage disequilibrium (LD) spans only short genomic distances. In contrast, in captive populations, where LD blocks are large, apparent SNP effects on morphological traits (i.e. associations) were highly repeatable with independent data from the same population. Most of those SNPs also showed significant associations with the same trait in other captive populations, but the direction and magnitude of these effects varied among populations. This suggests that the tested SNPs are not the causal QTN but rather physically linked to them, and that LD between SNPs and causal variants differs between populations due to founder effects. While the identification of QTN remains challenging in nonmodel organisms, we illustrate that it is indeed possible to confirm the location and magnitude of QTL in a population with stable linkage between markers and causal variants.
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| 13. |
- Knief, Ulrich, et al.
(författare)
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QTL and quantitative genetic analysis of beak morphology reveals patterns of standing genetic variation in an Estrildid finch
- 2012
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 21:15, s. 3704-3717
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Tidskriftsartikel (refereegranskat)abstract
- The intra- and interspecific diversity of avian beak morphologies is one of the most compelling examples for the power of natural selection acting on a morphological trait. The development and diversification of the beak have also become a textbook example for evolutionary developmental biology, and variation in expression levels of several genes is known to causally affect beak shape. However, until now, no genomic polymorphisms have been identified, which are related to beak morphology in birds. QTL mapping does reveal the location of causal polymorphisms, albeit with poor spatial resolution. Here, we estimate heritability and genetic correlations for beak length, depth and width and perform a QTL linkage analysis for these traits based on 1404 informative single-nucleotide polymorphisms genotyped in a four-generation pedigree of 992 captive zebra finches (Taeniopygia guttata). Beak size, relative to body size, was sexually dimorphic (larger in males). Heritability estimates ranged from 0.47 for beak length to 0.74 for beak width. QTL mapping revealed four to five regions of significant or suggestive genome-wide linkage for each of the three beak dimensions (nine different regions in total). Eight out of 11 genes known to influence beak morphology are located in these nine peak regions. Five QTL do not cover known candidates demonstrating that yet unknown genes or regulatory elements may influence beak morphology in the zebra finch.
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| 14. |
- Lindholm, Anna K., et al.
(författare)
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The Ecology and Evolutionary Dynamics of Meiotic Drive
- 2016
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Ingår i: Trends in Ecology & Evolution. - : Elsevier BV. - 0169-5347 .- 1872-8383. ; 31:4, s. 315-326
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Forskningsöversikt (refereegranskat)abstract
- Meiotic drivers are genetic variants that selfishly manipulate the production of gametes to increase their own rate of transmission, often to the detriment of the rest of the genome and the individual that carries them. This genomic conflict potentially occurs whenever a diploid organism produces a haploid stage, and can have profound evolutionary impacts on gametogenesis, fertility, individual behaviour, mating system, population survival, and reproductive isolation. Multiple research teams are developing artificial drive systems for pest control, utilising the transmission advantage of drive to alter or exterminate target species. Here, we review current knowledge of how natural drive systems function, how drivers spread through natural populations, and the factors that limit their invasion.
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| 15. |
- Mueller, Jakob C., et al.
(författare)
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Micro Germline-Restricted Chromosome in Blue Tits : Evidence for Meiotic Functions
- 2023
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Ingår i: Molecular biology and evolution. - : Oxford University Press. - 0737-4038 .- 1537-1719. ; 40:5
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Tidskriftsartikel (refereegranskat)abstract
- The germline-restricted chromosome (GRC) is likely present in all songbird species but differs widely in size and gene content. This extra chromosome has been described as either a microchromosome with only limited basic gene content or a macrochromosome with enriched gene functions related to female gonad and embryo development. Here, we assembled, annotated, and characterized the first micro-GRC in the blue tit (Cyanistes caeruleus) using high-fidelity long-read sequencing data. Although some genes on the blue tit GRC show signals of pseudogenization, others potentially have important functions, either currently or in the past. We highlight the GRC gene paralog BMP15, which is among the highest expressed GRC genes both in blue tits and in zebra finches (Taeniopygia guttata) and is known to play a role in oocyte and follicular maturation in other vertebrates. The GRC genes of the blue tit are further enriched for functions related to the synaptonemal complex. We found a similar functional enrichment when analyzing published data on GRC genes from two nightingale species (Luscinia spp.). We hypothesize that these genes play a role in maintaining standard maternal inheritance or in recombining maternal and paternal GRCs during potential episodes of biparental inheritance.
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| 16. |
- Pei, Yifan, et al.
(författare)
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Occasional paternal inheritance of the germline-restricted chromosome in songbirds
- 2022
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences (PNAS). - 0027-8424 .- 1091-6490. ; 119:4
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Tidskriftsartikel (refereegranskat)abstract
- Songbirds have one special accessory chromosome, the so-called germline-restricted chromosome (GRC), which is only present in germline cells and absent from all somatic tissues. Earlier work on the zebra finch (Taeniopygia guttata castanotis) showed that the GRC is inherited only through the female line-like the mitochondria-and is eliminated from the sperm during spermatogenesis. Here, we show that the GRC has the potential to be paternally inherited. Confocal microscopy using GRC-specific fluorescent in situ hybridization probes indicated that a considerable fraction of sperm heads (1 to 19%) in zebra finch ejaculates still contained the GRC. In line with these cytogenetic data, sequencing of ejaculates revealed that individual males from two families differed strongly and consistently in the number of GRCs in their ejaculates. Examining a captive-bred male hybrid of the two zebra finch subspecies (T. g. guttata and T. g. castanotis) revealed that the mitochondria originated from a castanotis mother, whereas the GRC came from a guttata father. Moreover, analyzing GRC haplotypes across nine castanotis matrilines, estimated to have diverged for up to 250,000 y, showed surprisingly little variability among GRCs. This suggests that a single GRC haplotype has spread relatively recently across all examined matrilines. A few diagnostic GRC mutations that arose since this inferred spreading suggest that the GRC has continued to jump across matriline boundaries. Our findings raise the possibility that certain GRC haplotypes could selfishly spread through the population via occasional paternal transmission, thereby out-competing other GRC haplotypes that were limited to strict maternal inheritance, even if this was partly detrimental to organismal fitness.
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| 17. |
- Pei, Yifan, et al.
(författare)
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Weak antagonistic fitness effects can maintain an inversion polymorphism
- 2023
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Ingår i: Molecular Ecology. - : John Wiley & Sons. - 0962-1083 .- 1365-294X. ; 32:13, s. 3575-3585
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Tidskriftsartikel (refereegranskat)abstract
- The study of chromosomal inversion polymorphisms has received much recent attention, particularly in cases where inversions have drastic effects on phenotypes and fitness (e.g. lethality of homozygotes). Less attention has been paid to the question of the maintenance of inversion polymorphisms that show only weak effects. Here, we study the maintenance of such an inversion polymorphism that links 250 genes on chromosome Tgu11 in the zebra finch (Taeniopygia guttata). Based on data from over 6000 captive birds, we estimated the effects of this inversion on a wide range of fitness-related traits. We found that, compared with the ancestral allele A, the inverted allele D had small additive beneficial effects on male siring success and on female fecundity. These fitness-enhancing effects may explain the initial spread of the derived D allele (allele frequency 53%). However, individuals that were homozygous for D had a slightly lower survival rate, which may explain why the D allele has not spread to fixation. We used individual-based simulations to examine how an inversion polymorphism with such antagonistic fitness effects behaves over time. Our results indicate that polymorphisms become stabilized at an intermediate allele frequency if the inversion links an additively beneficial allele of small effect size to a recessive weakly deleterious mutation, overall resulting in weak net heterosis. Importantly, this conclusion remains valid over a wide range of selection coefficients against the homozygous DD (up to lethality), suggesting that the conditions needed to maintain the polymorphism may frequently be met. However, the simulations also suggest that in our zebra finch populations, the estimated recessive deleterious effect of the D allele (on survival in captivity) is not quite large enough to prevent fixation of the D allele in the long run. Estimates of fitness effects from free-living populations are needed to validate these results.
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| 18. |
- Schielzeth, Holger, et al.
(författare)
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QTL linkage mapping of wing length in zebra finch using genome-wide single nucleotide polymorphisms markers
- 2012
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 21:2, s. 329-339
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Tidskriftsartikel (refereegranskat)abstract
- Avian wing length is an important trait that covaries with the ecology and migratory behaviour of a species and tends to change rapidly when the conditions are altered. Long-distance migrants typically have longer wings than short-distance migrants and sedentary species, and long-winged species also tend to be more dispersive. Although the substantial heritability of avian wing length is well established, the identification of causal genes has remained elusive. Based on large-scale genotyping of 1404 informative single nucleotide polymorphisms (SNP) in a captive population of 1067 zebra finches, we here show that the within-population variation of relative wing length (h(2) = 0.74 +/- 0.05) is associated with standing genetic variation in at least six genomic regions (one genome-wide significant and five suggestive). The variance explained by these six quantitative trait loci (QTL) sums to 36.8% of the phenotypic variance (half of the additive genetic variance), although this likely is an overestimate attributable to the Beavis effect. As avian wing length is primarily determined by the length of the primary feathers, we then searched for candidate genes that are related to feather growth. Interestingly, all of the QTL signals co-locate with Wnt growth factors and closely interacting genes (Wnt3a, Wnt5a, Wnt6, Wnt7a, Wnt9a, RhoU and RhoV). Our findings therefore suggest that standing genetic variation in the Wnt genes might be linked to avian wing morphology, although there are many other genes that also fall within the confidence regions.
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| 19. |
- Schielzeth, Holger, et al.
(författare)
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QTL linkage mapping of Zebra finch beak color shows an oligogenic control of a sexually selected trait
- 2012
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 66:1, s. 18-30
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Tidskriftsartikel (refereegranskat)abstract
- Mate choice based on sexual ornaments can impose strong selection, which raises the question of how genetic variation in ornaments is maintained. One mechanism that has been proposed is genic capture. If ornament expression is influenced by general condition and condition is under polygenic control, selection will be inefficient in removing genetic variation. Here we analyze whether the genetic architecture of beak color in a population of zebra finches supports this hypothesis. Zebra finch beak color is commonly assumed to be under strong selection by mate choice, although some of the evidence is ambiguous. We show that beak redness has a heritability of 34% in our population and that it is strongly genetically correlated between the sexes, suggesting that it is largely controlled by the same genes in males and females. We mapped variation in beak redness based on 1404 single-nucleotide polymorphism (SNP) markers genotyped in a large pedigree. We find evidence for linkage on four chromosomes (Tgu1, Tgu5, Tgu13, Tgu21), which together explain a large part of the additive genetic variance. Our finding of genomic regions with major additive effects is not consistent with directional selection and genic capture, but rather suggests a role of antagonistic pleiotropy in maintaining genetic variation.
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| 20. |
- Schielzeth, Holger, et al.
(författare)
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Quantitative genetics and fitness consequences of neophilia in zebra finches
- 2011
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Ingår i: Behavioral Ecology. - : Oxford University Press (OUP). - 1045-2249 .- 1465-7279. ; 22:1, s. 126-134
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Tidskriftsartikel (refereegranskat)abstract
- Consistent between-individual differences in context-general behavioral traits (often called personality traits) are particularly interesting for behavioral ecologists because they might show unexpected cross-context correlations and explain maladaptive behavior. In order to understand their evolutionary significance, it is relevant to know the heritability of these traits and how they relate to reproductive success. This might give insights into selective processes that maintain variation as well as into potential trade-offs. We scored approach to novel objects of 530 captive zebra finches in a familiar environment. Scores were highly repeatable and showed substantial additive genetic variation. We measured reproductive success, promiscuity, and extrapair paternity rates under aviary conditions and calculated linear and nonlinear selection differentials based on fertilization success as well as effects on chick-rearing success of pairs. Approach to novel objects had little influence on these components of reproductive success. However, we found that the social environment ( manipulated operational sex ratios) influenced the correlation between approach to a novel object and the proportion of extrapair paternity. We also found that the sex ratio manipulation affected measures of the intensity of sexual selection. Both effects were stronger in males than in females. We conclude that despite the lack of differences in overall reproductive success, approach to novel objects reflects variation in reproductive strategies.
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| 21. |
- Voelkl, Bernhard, et al.
(författare)
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Reproducibility of animal research in light of biological variation
- 2020
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Ingår i: Nature Reviews Neuroscience. - : Nature Publishing Group. - 1471-003X .- 1471-0048. ; 21, s. 384-393
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Tidskriftsartikel (refereegranskat)abstract
- In this Perspective, Hanno Wurbel and colleagues argue that a disregard for incorporating biological variation in study design is an important cause of poor reproducibility in animal research. They put the case for the use of systematic heterogenization of study samples and conditions in studies to improve reproducibility.Context-dependent biological variation presents a unique challenge to the reproducibility of results in experimental animal research, because organisms' responses to experimental treatments can vary with both genotype and environmental conditions. In March 2019, experts in animal biology, experimental design and statistics convened in Blonay, Switzerland, to discuss strategies addressing this challenge. In contrast to the current gold standard of rigorous standardization in experimental animal research, we recommend the use of systematic heterogenization of study samples and conditions by actively incorporating biological variation into study design through diversifying study samples and conditions. Here we provide the scientific rationale for this approach in the hope that researchers, regulators, funders and editors can embrace this paradigm shift. We also present a road map towards better practices in view of improving the reproducibility of animal research.
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| 22. |
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