PS112 (2018)
Species . | Cruises . | Location . | Sample size . |
---|---|---|---|
PS82 (2014) and PS96 (2016) | Weddell Sea | 14 | |
PS82 (2014) | Weddell Sea | 13 | |
ANT XIX/3 (2002) PS112 (2018) | Antarctic Peninsula | 11 | |
PS112 (2018) | Antarctic Sound | 7 | |
ANT XXVII/3 (2011) | South Orkneys | 11 | |
PS82 (2014) | Weddell Sea | 9 | |
Total | 38 | ||
ANT XXVIII/4 (2012) | Antarctic Peninsula | 10 | |
PS82 (2014) | Weddell Sea | 10 | |
Total | 20 | ||
85 |
The table reports species names, sampling cruises, general area of sampling (location), and sample size. All samples were collected in collaboration with the Alfred Wegner Institute Helmholtz Centre for Polar and Marine Research (AWI, Bremerhaven, Germany) during R/V Polarstern cruises. #Antarctic Peninsula indicates: South Shetlands and Elephant Island.
Samples of C. hamatus and C. myersi were collected from the Weddell Sea ( Fig. 1 ; samples from Schiavon et al. 2021 ). Samples of C. rastrospinosus analysed in this study belong to four main geographic areas: South Shetland and Elephant Islands (on the western side and north of the Antarctic Peninsula; both grouped here as ‘Antarctic Peninsula’ for brevity), Antarctic Sound (on the eastern side of the Antarctic Peninsula), Weddell Sea, and South Orkney Islands ( Fig. 1 ; samples from Schiavon et al. 2021 ). Chaenodraco wilsoni , a geographically widespread sister species of the genus Chionodraco (Near et al. 2012 ), was used as outgroup and specimens were collected from the Weddell Sea and the Antarctic Peninsula ( Fig. 1 ).
Map of sampling sites around the Antarctic Peninsula and in the Weddell Sea. Dots indicate the average locations of sampling for the four species analysed in this study. Map drawn with the R package ggOceanMaps 1.1 (Vihtakari 2024 ) and modified manually.
The dataset analysed in this study included 65 specimens of the 3 Chionodraco species ( Table 1 ): 14 C. hamatus (12 pure + 2 putatively admixed with major contribution to their genetic variability from C. hamatus ); 13 C. myersi (10 pure + 2 putatively hybrids as defined in Schiavon et al. 2021 , and 1 putatively admixed with major genetic contribution from C. myersi ); and 38 C. rastrospinosus (32 pure + 6 putatively admixed with major contribution to their genetic variability from C. rastrospinosus ). The dataset also included 20 C. wilsoni . The following sections report a summary of the methods; see Supplementary Materials for details (section ‘Extended Materials and Methods’).
DNA extraction, integrity check, and concentration measurement followed Pardo et al. (2005 ) and Schiavon et al. (2021 ). Preparation of the RADseq library using the single restriction enzyme sbfI followed Etter et al. ( 2011 ) with modifications as described in Ceballos et al. (2019 ). Paired-end sequencing with a read length of 150 bp was conducted on the Illumina HiSeq4000 platform at the Genomics and Cell Characterization Core Facility (GC3F, University of Oregon, USA). Raw reads were demultiplexed with Stacks 2.53 (Rochette et al. 2019 ), aligned to the genome of C. myersi (Bargelloni et al. 2019 ), using BWA 0.7.17 (Li and Durbin 2009 ), and SNPs were called with Stacks 2.53 .
Given that C. rastrospinosus specimens were collected in different locations, we performed a preliminary assessment of population structure for this species. We repeated the SNP calling as reported in Supplementary Material , but only with C. rastrospinosus to maximize the number of called SNPs.
We prepared datasets for all downstream analysis with VCFtools 0.1.17 (Danecek et al. 2011 ). Datasets were generated according to the guidelines and properties of the different software as described in the next sections, in Supplementary Table S1 and Supplementary Fig. S1 , and in the Supplementary Material .
We first estimated the degree of differentiation at the intra- and inter-specific scales to investigate patterns of admixture among species ( Supplementary Table S1 ). We considered samples collected from different geographic sites for a more accurate assessment of interspecific gene flow, whereas patterns of population differentiation will be investigated in a separate study (not discussed here). The relative positions of species (and population samples for C. rastrospinosus , given that this species was sampled in more than one geographic location) were visualized in multidimensional genetic space by principal coordinate analysis (PCoA) as implemented in ‘adegenet’ 2.1.3 (Jombart 2008 ). Shared coancestry between species was analysed with fineRADstructure (Malinsky et al. 2018 ) ( Supplementary Table S1 ).
We first applied fineRADstructure and the PCoA to all Chionodraco species to identify individuals with putative admixed ancestry. Hence, an unsupervised hierarchical clustering was performed using Admixture 1.3.0 (Alexander et al. 2009 ). Admixture was run to estimate individual ancestry proportions ( Q ) with cross-validation assuming a value of K = 2–11 for the estimation of the optimal number of clusters.
Since PCoA, Admixture , and fineRADstructure do not explicitly fit a historical model and do not allow the inference of number of historical admixture events (Malinsky et al. 2020 ), we used TreeMix 1.13 (Pickrell and Pritchard 2012 ) ( Supplementary Table S1 ) to examine introgression between branches of the Chionodraco phylogeny, using C. wilsoni as outgroup. The method implemented in TreeMix first infers a maximum likelihood (ML) tree to model the relationship among population/species. Then, it adds migration edges between branches that poorly fit to the tree (Brauer et al. 2023 ).
To assess gene flow between Chionodraco species and estimate the proportion of the genome affected by introgression, Patterson’s D (ABBA-BABA test) and the f 4 ‐ratio statistics were calculated as formal tests for past introgresson in Dsuite (Malinsky et al. 2020 ) ( Supplementary Table S1 ) and the function Dtrios .
Additional analyses with TreeMix (testing 1–10 migration edges) and Dsuite ( Supplementary Table S1 ) were applied to test if certain population samples of C. hamatus and C. rastrospinosus were more involved in introgression events than others.
To understand whether all genomic regions were equally affected by introgression, we ordered and oriented C. myersi scaffolds (not assembled at chromosome level, Bargelloni et al. 2019 ) into pseudo-chromosomes according to chromosome subdivision in Dissostichus mawsoni (Lee et al. 2021 , same number of chromosomes as Chionodraco spp., Ozouf-Costaz 1987 ) using RagTag (Alonge et al. 2022 ) and repeated SNP calling and Dsuite analysis ( Supplementary Table S1 ).
To further investigate the relationships among Chionodraco species, to reconstruct the species demographics, and to account for the presence of ILS as detected with Dsuite (see Results), we applied Bayesian phylogenetic inference by using the multispecies coalescent model implemented in SNAPP 1.3 (Bryant et al. 2012 ) for BEAST2 2.6.3 (Bouckaert et al. 2014 ) ( Supplementary Table S1 ).
Based on the results from Dsuite and SNAPP, we investigated scenarios of gene flow that may have shaped the evolutionary history of the genus Chionodraco using fastsimcoal 2.6 (Excoffier et al. 2013 ) ( Supplementary Table S1 ). The principle behind fastsimcoal is that different patterns of gene flow and demographic events shape the distribution of allele frequencies at polymorphic loci in one or several populations in specific ways (e.g. two populations will have more similar allele frequencies if they are strongly connected or recently split; Bourgeois and Warren 2021 ). Three population genetics models were tested: (i) complete isolation with no gene flow; (ii) continuous gene flow between C. hamatus and C. myersi ; and (iii) intermittent gene flow between C. hamatus and C. myersi during interglacial periods (based on Lisiecki and Raymo 2005 ; from 14 kya to the present, 130–115 kya, 337–300 kya, and 424–374 kya).
Gene flow estimates obtained by fastsimcoal are expressed as the probability for any lineage to move between two populations per generation. To make the implications of these results easier to understand, gene flow estimates are here reported as number of diploid individuals in the sink population that derived from the source population per generation and were calculated as Nm ij = m ij × N ej (raw migration rate × effective population size of the sink population).
The first two principal components (PC) of the PCoA recovered four well-separated clusters, corresponding to the four species ( Fig. 2 ). The fourth PC distinguished two groups inside C. hamatus ( Supplementary Fig. S2 ).
Scatter plot of PCoA and admixture plot inset based on 36 582 SNPs for the three Chionodraco species and C. wilsoni . Labels on the axes indicate the contributions of the displayed principal components to the variance. Admixture plot represents individual membership probabilities to the three Chionodraco species and C. wilsoni ( K = 4) given by Admixture . Each individual is represented by a vertical lane, the proportion of different colours in each lane is proportional to the probability of assignment to each species.
The PcoA for C. rastrospinosus showed intraspecific geographic differences, separating three groups of samples according to geography: (i) Antarctic Peninsula + Antarctic Sound, (ii) South Orkney Islands, and (iii) Weddell Sea ( Supplementary Fig. S3 ).
Estimation of individual ancestries made by Admixture indicated K = 4 as the optimal number of genetic clusters ( Supplementary Fig. S4 ). In contrast to Schiavon et al. (2021 ), all individuals analysed in this study were of pure ancestry, with none showing admixture ( Fig. 2 , inset).
In agreement with results of Admixture , the co-ancestry matrix inferred by fineRADstructure recovered four clusters corresponding to the number of species expected in the dataset ( Fig. 3 ). Additionally, fineRADstructure supported the existence of two groups within C. hamatus (hereafter C. hamatus -a, N = 10 and C. hamatus -b, N = 4, Fig. 3 ). Homogeneous haplotype sharing was inferred among Chionodraco species, indicating that none of the individuals could be considered admixed.
Clustered fineRADstructure coancestry matrix inferred for the three Chionodraco species and C. wilsoni . Each row and each column, include the same individuals compared to one another. Coancestry ranges from weak (yellow) to strong (blue) as indicated by the colour scale, with darker blue and purple colours in the matrix indicating larger proportions of loci with shared coancestry. Black solid contour lines indicate the species clusters. Black dashed lines delimit the three species of genus Chionodraco . White solid lines indicate two subgroups of C. hamatus: C. hamatus -a, N = 10 and C. hamatus -b, N = 4.
The maximum likelihood phylogenetic tree, generated by TreeMix , agreed with the relationships of the four taxa in the tree by Near et al. ( 2018 ), using RADseq loci. With migration edges added to the tree, the program indicated one gene-flow event from C. hamatus to C. myersi ( Fig. 4 and Supplementary Fig. S5 ). Plotting the residuals showed that the addition of the migration edge increased the fit of the model to the data ( Supplementary Fig. S6 ). When differentiation within C. hamatus and C. rastrospinosus was considered based on PCoA and fineRADstructure results ( Figs 2 and 3 , Supplementary Figs S2 and S3 ), introgression events were inferred for all population pairs, limited only by the number of migration edges allowed ( Supplementary Figs S7 and S8 ).
Maximum likelihood tree of Chionodraco spp. and C. wilsoni estimated by TreeMix . The red arrow indicates inferred unidirectional interspecific gene flow from C. hamatus to C. myersi . Migration weights range from low (yellow) to high (red), as indicated by the colour scale and correspond to the proportion of alleles that the receiving species gained from the donor species.
Analysis with Dsuite showed that only 40.9% of the test-informative sites were concordant with the phylogeny (BBAA sites, which placed C. hamatus and C. rastrospinosus as sister species), indicating that all species had a large number of shared alleles ( Table 2 ). The ABBA pattern (indicating allele sharing between C. hamatus and C. myersi ) characterized 34.4% of the sites, whereas 24.7% of the sites had the BABA pattern (allele sharing between C. myersi and C. rastrospinosus ). The difference between the numbers of ABBA and BABA patterns is statistically significant ( D = 0.163, P < 0.001), rejecting ILS as the only cause of allele sharing between non-sister species, and thus positing introgression between C. hamatus and C. myersi . The admixture proportion estimated by the f 4 ‐ratio was 13.6% ( Table 2 ).
Results of Dsuite for the detection of introgression among the Chionodraco species.
P1 . | P2 . | P3 . | statistic . | Z-score . | -value . | ‐ratio . | BBAA . | ABBA . | BABA . |
---|---|---|---|---|---|---|---|---|---|
0.164 | 9.671 | <0.001 | 0.136 | 1516.190 | 1276.610 | 917.731 |
P1 . | P2 . | P3 . | statistic . | Z-score . | -value . | ‐ratio . | BBAA . | ABBA . | BABA . |
---|---|---|---|---|---|---|---|---|---|
0.164 | 9.671 | <0.001 | 0.136 | 1516.190 | 1276.610 | 917.731 |
P1, P2, and P3 indicate the position of the species in the phylogenetic tree. If the value of the D -statistic is statistically different from zero, introgression is inferred. The f 4 ‐ratio indicates the admixture proportion. “BBAA” indicates the number of sites at which P1 and P2 share the same allele to the exclusion of P3 and P4, "ABBA" the number of sites with alleles shared between P2 and P3, and “BABA” the number of sites with alleles shared between P1 and P3.
When considering differentiated populations (for C. rastrospinosus ) and groups (for C. hamatus ) ( Supplementary Table S2 ), Dsuite supported introgression between C. hamatus and C. myersi , but primarily for C. hamatus -b. Introgression between C. rastrospinosus and C. hamatus was detected by including differentiated populations. However, D values between C. hamatus and C. rastrospinosus were ∼10 times smaller than those between C. hamatus and C. myersi ( Supplementary Table S2 ). Of the C. rastrospinosus populations, the Weddell Sea population appeared most involved in introgression events ( D -statistics ranging from 0.013 to 0.027, f 4 -ratios ranging from 0.007 to 0.022; Supplementary Table S2 ).
Analysis at chromosome level indicated that 15 of 24 pseudo-chromosomes (and the extra pseudo-chromosome combining all the unmapped contigs) supported introgression between C. hamatus and C. myersi ( Supplementary Table S3 ).
Phylogenetic inference with SNAPP and the molecular clock assumption returned a single tree with full support at each node (topology in agreement with Near et al. 2018 ) ( Fig. 5 ). The divergence events of the four species were estimated to have occurred 1.5 Mya for C. wilsoni (0.8–2.3 Mya 95% height posterior density—HPD interval), 0.9 Mya for C. myersi (0.5–1.4 Mya 95% HPD interval), and 0.5 Mya for the split between C. hamatus and C. rastrospinosus (0.3–0.8 Mya 95% HPD interval). The analysis allowing different N e per branch indicated an increase of one order of magnitude in the effective population size from basal to terminal branches ( Fig. 5 ).
Time-calibrated phylogeny of Chionodraco spp. and C. wilsoni inferred by SNAPP and rendered as a cloud tree. Time is shown on the x -axis in Mya. Numbers along the branches indicate the estimates of N e when SNAPP was set up to allow a different N e on each branch.
In the analysis with fastsimcoal , the models with gene flow (models 2 and 3) received the greatest support, whereas the model with no gene flow (model 1) was less probable ( Fig. 6 ). The model with continuous gene flow (model 2) and the model with gene flow during interglacial times (model 3) had overlapping likelihood distributions, indicating that both models fit the observed data similarly well, although the model with gene flow only during interglacial (model 3) had slightly larger likelihood values. The estimated numbers of migrants per generation were small in both cases (model 2: C. hamatus → C. myersi = 0.25; C. myersi → C . hamatus = 0.04; model 3: C. hamatus → C. myersi = 0.76; and C. myersi → C . hamatus = 0.92).
Different gene flow models simulated with fastsimcoal and corresponding likelihood support. Chionodraco myersi is shown in yellow, C. hamatus in red, and C. rastrospinosus in blue. The first model portrays the evolutionary tree of the species as inferred by SNAPP, with no gene flow allowed. In the second model, continuous gene flow between C. hamatus and C. myersi is maintained after the species divergence. In the third model, gene flow between C. hamatus and C. myersi is allowed only during interglacial times. The width of the rectangles is proportional to the effective population size estimated with SNAPP. The time axis reports the splitting times estimated with SNAPP. In the third model, interglacial periods are marked in orange. The boxplots represent the likelihood distributions of the three simulated models. The black solid line indicates the median value; whiskers extend to minimum and maximum values.
The site-frequency spectra, SFS, were similar among the three models, and in all cases, there was a good similarity between the observed and the expected SFS ( Supplementary Figs S9 and S11 ). The SFS of C. hamatus and C. rastrospinosus had the weakest correspondence between observed and expected results for all the models; expected SFS showed less fixed sites than observed for both species.
Distinguishing between alternative scenarios of introgression is important for understanding the speciation process and the evolution of the cryonotothenioid lineage since ancient hybridization may have facilitated the evolution of species diversity in icefish (Near et al. 2006 ), as in other adaptive fish radiations (e.g. cichlid fish; Meier et al. 2017 ). With the present work, we aimed to shed light on unresolved questions related to the occurrence of hybridization and introgression in the genus Chionodraco . We first confirmed the findings by Marino et al. (2013 ) and Schiavon et al. (2021 ) of three genetically distinct Chionodraco species. Second, we provide new genomic evidence that past hybridization and introgression played a role in the evolution of this genus of icefish.
The evidence of past introgression brought up by demographic modelling and phylogenetic reconstruction is in agreement with previous studies suggesting that interspecific gene flow characterized the genus Chionodraco after species diversification, likely during interglacial periods (Marino et al. 2013 ). However, we could not confirm the signals of ongoing hybridization observed previously with microsatellite data (Marino et al. 2013 , Schiavon et al. 2021 ). Moreover, this study, for the first time, found evidence that ancient hybridization and introgression occurred mostly between the two sympatric species C. hamatus and C. myersi . Even though our results do not provide an indication of contemporary interspecific gene flow between Chionodraco species, we cannot exclude this possibility. Individuals from areas not sampled by this study might reveal evidence of it. We also caution on using a few markers to draw conclusions about time scale and extent of interspecific gene flow. Finally, we emphasize the importance of these types of studies to aid prediction of future interaction and compatibility among species and underscore the conservation value of introgressed populations (Hansen 2023 ).
RADseq data identified individual genetic clusters for each of the three Chionodraco species and C. wilsoni , confirming the three species are well separated despite their partially overlapping geographic distributions. In contrast with earlier work with microsatellites (Marino et al. 2013 , Schiavon et al. 2021 ), PCoA showed no individuals with an intermediate genotype between species (putative contemporary hybrids), and the analyses to infer individual ancestry ( Admixture and fineRADstructure) did not detect hybrid individuals.
Although the three Chionodraco species are clearly separated in the PCoA and Admixture analyses, testing for hybridization using the D -statistics showed that fewer than half (∼41%) of the sites were concordant with the phylogeny. This result suggests that the three Chionodraco species share a great amount of genetic polymorphisms, which, at least partially, is likely due to ILS. D -statistics strongly supported interspecific gene flow between C. hamatus and C. myersi (with an admixture proportion, f 4 -ratio, 13.6%) and showed that C. hamatus and C. myersi share more alleles than C. rastrospinosus and C. myersi . Also, the analysis at chromosome level indicated that introgression is widespread along the genome, as D values were statistically different from 0 for 15 of 24 chromosomes. Also considering results from fineRADstructure , which showed a similar amount of coancestry for all pairs of individuals, we posit that interspecific gene flow likely occurred in the past and involved the common ancestors of the individuals we analysed.
Gene flow estimates by TreeMix confirmed evidence of a past introgression event and showed that this has likely occurred from C. hamatus to C. myersi . TreeMix reconstructed a pattern of interspecific gene flow i.e. asymmetric and different from that originally proposed by Marino et al. (2013 ) based on microsatellites and approximate Bayesian computation (ABC) simulations. Marino et al. (2013 ) estimated smaller rates of migrant exchange (about two individuals per generation) between C. myersi and C. hamatus than between the other two Chionodraco species pairs ( C. hamatus/C. rastrospinosus and C. myersi/C. rastrospinosus ).
We tested different scenarios of gene flow between C. hamatus and C. myersi via demographic modelling ( fastsimcoal analysis) to further investigate past introgression under the hypotheses that the species may either have shared geographic ranges continuously (which would have allowed for continuous interspecific gene flow) or been spatially separated temporarily (which would have allowed for interspecific gene flow during secondary contacts). We evaluated three models: no gene flow, continuous gene flow, and gene flow only during interglacial times. The first scenario received the least support, confirming the presence of introgression detected by TreeMix and D -statistics. The second and third scenarios received similar support, with slightly larger likelihoods for the scenario with gene flow only during interglacial times. This agrees with results of ABC simulations by Marino et al. (2013 ), who found similar support for the models with inter-specific gene flow although the greatest probability was observed for the more complex model, in which migration was allowed only during interglacial periods. This lack of power to discriminate among models makes it difficult to understand whether C. hamatus and C. myersi had the possibility to mate throughout their evolutionary history or whether they were temporarily separated by glaciation events. However, in both cases, interspecific gene flow estimates were very small (less than one migrant per generation). In combination with the absence of contemporary putative hybrid individuals in our dataset, this points toward the occurrence of rare introgression events in the evolutionary history of the genus.
Interspecific gene flow between C. hamatus and C. myersi may be explained by their phylogenetic proximity. After the divergence of the two lineages, interspecific hybridization may have continued occasionally until reproductive isolation was complete. Nonetheless, although no current hybrids were identified in the RADseq analysis, the possibility that the two species are still interfertile cannot be ruled out. Moreover, we cannot exclude the possibility that limited interspecific gene flow may have occurred for other species combinations. The hypothesis that hybridization and introgression may have characterized other Chionodraco species pairs is indirectly supported by experimental evidence showing that even a cross between two genera of icefish ( C. aceratus and C. rastrospinosus ) can still produce viable offspring (Desvignes et al. 2019 ). In addition, even though we cannot exclude that the few cases of mitochondrial-nuclear discordance reported by Schiavon et al. (2021 ) and Marino et al. (2013 ) were due to ILS, shared mitochondrial D-loop haplotypes suggest introgression between C. hamatus and C. rastrospinosus .
Besides phylogenetic proximity, past introgression might have been favoured by the geographic context of speciation in Chionodraco . Situations previously ascribed to sympatric speciation have been reinterpreted as allopatric speciation followed by secondary contact (Lucek et al. 2018 , Dean et al. 2019 ). If this were applicable to the genus Chionodraco , we would expect that the ancestor of C. hamatus and C. rastrospinosus initially diverged from C. myersi due to geographic isolation (e.g. in glacial refugia, allopatric speciation). Subsequently, a secondary contact during interglacial periods may have allowed introgression between C. hamatus and C. myersi . However, some introgression may have occurred during the early phases of the divergence between C. rastrospinosus and C. hamatus (as suggested by D -statistics). Subsequently, C. rastrospinosus may have remained in geographic isolation in the Antarctic Peninsula, or may have had small population size and patchy distribution in sympatry, e.g. in the Weddell Sea (Schiavon et al. 2021 ), thus limiting the potential of introgression with the other Chionodraco species. This scenario may explain both the introgression between C. hamatus and C. myersi found by TreeMix, FineRADstructure , and D -statistics and the signal of introgression between C. rastrospinosus and C. hamatus found only by D -statistics.
Differences in life-history traits may explain the low levels of introgression between C. hamatus and C. myersi . Although living in sympatry, the two species may be reproductively separated by different mating habits. The reproductive period of C. hamatus spans from January to March, but for C. myersi , it lasts from July to September (Ekau 1991 , Vacchi et al. 1996 , La Mesa et al. 2013 ). Additionally, the nesting behaviour that characterizes these fish (Ferrando et al. 2014 ) is usually species-specific, which may also prevent hybridization (Desvignes et al. 2019 ). However, reproductive behavioural data for Chionodraco spp. come from few, sporadic observations and provide only an incomplete picture of the species’ ecology. Moreover, it was observed that the reproductive periods of some notothenioids (e.g. Gobionotothen gibberifrons, Nototheniops larseni , and the icefish C. aceratus ) change with latitude, possibly following a temperature gradient (Papetti et al. 2007 ). Thus, past climatic oscillations may have promoted occasional overlaps in the times of reproduction in C. hamatus and C. myersi , in agreement with the notion that notothenioid demographic and evolutionary history is closely linked to climate history. This connection raises concerns about the potential impact of the current warming of the Southern Ocean on the survival of Antarctic marine fauna and the maintenance of genetic diversity. Periodic surveys are essential to monitor the genetic variability of these species, especially in areas of potential secondary contact. Such monitoring is crucial for management and to identify early changes in the distributions of potentially hybridizing species. This is particularly relevant in the implementation of marine protected areas.
The authors would like to thank Nils Koschnick (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, AWI, Bremerhaven, Germany) and the ship crew for their excellent contribution and support in collecting samples onboard the R/V Polarstern. The authors are grateful to Massimiliano Babbucci and Alessandra Battistotti (University of Padova, Italy) for insightful comments during data analysis. We also thank Giuditta Codogno and Ilaria Anna Maria Marino for their help with the lab work.
The authors have no conflict of interest to declare.
This research was supported by the European Marie Curie project ‘Polarexpress’ grant no. 622320 and the University of Padova BIRD grant no.164793 to Chiara Papetti. Michael Matschiner acknowledges funding from the Research Council of Norway (RCN) project no. 335549, Lorenzo Zane acknowledges support by the Italian National Programme of Antarctic Research (PNRA) project 2016_00 307, and Mario La Mesa acknowledges support by the Italian National Programme of Antarctic Research (PNRA) project BIOCLEVER PNRA19_00015-A2. Felix Mark and Magnus Lucassen acknowledge the support by the Helmholtz research programme ‘Changing Earth—Sustaining Our Future’.
LS and CP designed the research. CP, LZ, ER, ML, and FCM conducted the sampling. LS, CP, and SGC conducted molecular lab work. RF and EB provided help for the molecular lab work. LS analysed the data. MM, AW, SGC and ET provided help with data analysis. LS and CP wrote the original draft. All co-authors reviewed the manuscript.
Fish were sampled and processed according to and within laws, guidelines, and policies of the German and European Animal Welfare legislation. Sample collection during the cruises with the R/V Polarstern was approved by the competent German authority for Antarctic research, the UBA (Umweltbundesamt).
All the codes, datasets, and accessory files needed to replicate the analyses are available at https://github.com/Papetti-Lab/Chionodraco_gene_flow.git . Raw sequence reads are available under the NCBI BioProject Accession number: PRJNA1041981 ( https://www.ncbi.nlm.nih.gov/bioproject/PRJNA1041981/ ).
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Twenty-seven contestants will compete for the title of Miss Ohio in the week ahead, with the winner crowned June 15 at the Renaissance Theatre in Mansfield and becoming eligible to compete at Miss America in January.
Twelve contestants will vie June 12 for the title of Miss Ohio's Teen at the Renaissance Theatre. The teen winner also will compete at the national level. Current Miss Ohio Madison Miller and Miss Ohio's Teen Paisley French will emcee the teen competition.
Go to rentickets.org for tickets.
Here are brief biographies of the pageant contestants.
2023: Madison Miller, pianist from Coshocton, is crowned Miss Ohio in Mansfield ceremony
2023: Paisley French, 18, of Wheelersburg, is new Miss Ohio's Teen
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BA in History. The most striking thing about History at Oxford is its extraordinary range of choices. We offer more than 100 different options, reflecting the breadth of interests and expertise amongst the c. 150 professional historians who teach here. You can study options on African, Asian, American, British, European, and Global and ...
David, who is now a history teacher, says: 'A History degree was a prerequisite to teaching history to A-level and IB, but the Oxford degree accelerated my career path, allowing me to step straight into a position at an academic school. I use my degree on a daily basis, in teaching a wide range of historical topics as well as advising ...
History Courses. As the History Faculty at Oxford is large, we have tutors with a wide-range of specialist areas, and can therefore offer undergraduates a varied and flexible timetable. Students must study a variety of time periods, places, and approaches to history, but choose their own options within this framework and are free to follow ...
Every year Oxford's History Faculty admits around 300 students to study for an undergraduate degree in history. These students join a community of more than 1,500 Oxford historians - undergraduates, graduates, researchers, and tutors This intellectual variety allows the History Faculty to offer an unparalleled number and range of courses. ...
History. Oxford's History course combines the examination of large regions over extended periods of time with more focused work on smaller social groups, shorter periods and particular themes. It provides a distinctive education by developing an awareness of the differing political, cultural, social and economic structures within past ...
The Oxford History Faculty is at the forefront of research. Careers History graduates go on to follow diverse careers in fields such as the law, investment banking and consultancies, advertising, accountancy, the Civil Service, publishing, journalism and the media, global charity work, museums, librarianship and archive work, and teaching.
All studies; Ancient History; Europe; United Kingdom; England; University of Oxford; History (Ancient and Modern) About. The History (Ancient and Modern) course from the University of Oxford enables students to study history from the Bronze Age Mediterranean and Near East, through the Roman Empire, middle ages and early modern period, right up to British, European and World history in the ...
Advance your skills and methodology in researching local, regional and social history with this one-year, part-time online advanced diploma. Taught completely online, the course is taught at third-year undergraduate level. Discover our part-time undergraduate programmes in history, including local and social. Whether you wish to study for ...
Undergraduate Awards. Bachelor of Arts ()Bachelor of Fine Art ()The bachelor's degree is awarded soon after the end of the degree course (three or four years after matriculation).Contrary to common UK practice, Oxford does not award bachelor's degrees with honours; however, a student whose degree is classified third class or higher is considered "to have achieved honours status".
University of Oxford. / 51.75500°N 1.25500°W / 51.75500; -1.25500. The University of Oxford is a collegiate research university in Oxford, England. There is evidence of teaching as early as 1096, [2] making it the oldest university in the English-speaking world and the world's second-oldest university in continuous operation.
Post-interview: cGCSE 21.4% HAT 21.4% History written work 10.5%; English written work 10.5%; History interview 18.1%; English interview 18.1% History and Modern Languages Application stage
The Undergraduate Advanced Diploma in Local History is a one-year part-time course providing training in key concepts and methods of historical studies. It is delivered entirely online, so you can work at home with access to the course material, your tutor and fellow students. The course will help you improve the key skills you need for ...
Brazil was the last Western country to abolish slavery, which it did in 1888. As a colonial institution, slavery was present in all regions and in almost all free and freed strata of the population. Emancipation only became an issue in the political sphere when it was raised by the imperial government in the second half of the decade of the ...
Easier to pursue, as compared to an Honour's Degree. An Honour's degree requires more extensive research, as compared to a Bachelor's. The curriculum of a Bachelor's Degree focuses less on research and differs in the way knowledge is provided. An Honour's Degree allows students to study a number of subjects at once, all together.
According to the National Center for Education Statistics, students pursuing a bachelor's degree at a public four-year school paid an average in-state tuition of $9,596 in 2021-2022. Out-of-state students paid around $27,500, while students at private colleges paid an average of $34,041. The total cost of college varies by institution, so it's ...
ABC. Jenn Tran, the fan favorite who got Joey Graziadei's heart racing on "The Bachelor" this season, is ready to make her own mark on TV history as the first Asian-American Bachelorette. Only ...
Popular History Programs. 10. Humanities. Another one of the easiest online degrees, a bachelor's in humanities is an interdisciplinary track that covers areas like history, philosophy, religion, and literature.
Oxford High School principal Heath Harmon is the new Executive Director of the Alabama High School Athletic Association. Harmon was set to be officially introduced at a news conference Thursday ...
History in Oxford stretches from c 300 to the present, and embraces in addition to its British and European heritage an exceptionally broad range of World history. It comprises an active research community of up to 800 senior academics and graduate students, all contributing to a range of research seminars, lectures, academic societies, and ...
Luca Schiavon, Santiago G Ceballos, Michael Matschiner, Emiliano Trucchi, Mario La Mesa, Emilio Riginella, Magnus Lucassen, Felix C Mark, Kevin Bilyk, Rafaella Franch, Andreas Wallberg, Elisa Boscari, Lorenzo Zane, Chiara Papetti, Limited interspecific gene flow in the evolutionary history of the icefish genus Chionodraco, ICES Journal of Marine Science, Volume 81, Issue 4, May 2024, Pages 676 ...
Miss Ohio contestants. Miss Coshocton Aliah Williamson, 18, of Coshocton; talent, dance; She is majoring in biomedical engineering at The Ohio State University. Her platform is Heroes of Today ...
'A Muslim History of Oxford' Open Day 'A Muslim History of Oxford' Open Day 'A Muslim History of Oxford' Open Day. Wednesday 22 May. Faculty of History, University of Oxford 41-47 George Street Oxford OX1 2BE. Pause slideshow . move to carousel content. News.
Jenn, a 26-year-old physician's assistant student from Miami, had a strong connection with Joey on season 28 of "The Bachelor" and was one of the final six women in the competition.
cultures, film, history, language, linguistics, literature, people... Footprint on a cave floor. The Natural World. ... Find out more about Oxford's foundation year for talented students who have experienced disadvantage and educational disruption. Choosing your course.