• European Marine Science
• 2018-2022close
• Swiss National Science Foundation close

Phylogenetic analysis was performed using single copy ortholog genes identified with BUSCO, for the 24 newly sequenced notothenioid genomes and 17 previously published genomes of seven notothenioids and ten further species of percomorph fishes. BUSCO (v2) was run with lineage “actinopterygii_odb9”, and the sequences of single- opy orthologs identified in each assembly and extracted for use in further analysis. We used MAFFT v.7.453 to align 266 selected BUSCO genes that were single copy in our annotated gene sets. The 266 alignments were inspected by eye, and apparently misaligned sequence regions were set to missing data. A total of 1,141,524 amino acids were set to missing out of 6,410,688, including nine alignments that were excluded completely, leaving 257 alignments for further analysis. We then aligned nucleotide sequences of the same BUSCO genes according to the amino-acid alignments, ensuring that regions corresponding to the removed sequences were again set to missing data in the nucleotide sequence alignments. Sites with high entropy (entropy like score > 0.5) or high proportion of missing data (gap rate > 0.2) were removed with BMGE v.1.1 and alignments with more than three completely missing sequences, a minimum length below 500 bp, or a standard deviation of among-sequence GC-content variation greater than 0.03 were excluded. These filters were passed by 228 alignments. Each of these alignments was subjected to Bayesian phylogenetic analysis with BEAST 2 v.2.6.0, with an uncorrelated lognormal relaxed clock model and a Markov-chain Monte Carlo chain (MCMC) length of 25 million iterations. “Strict” and “permissive” sets of alignments were compiled based on estimates of the mutation rate and its among-species variation and contained 140 and 200 of the alignments, respectively. For the strict set of 140 alignments, the permissive set of 200 alignments, and the “full” set of 257 alignments, we performed maximum-likelihood phylogenetic analyses with IQ-TREE v.1.7 after alignment concatenation, maintaining separate partitions with unlinked instances of the GTR+Gamma substitution model for each of the original alignments. Node support was assessed with 1,000 ultrafast bootstrap replicates. Each of the three analyses was complemented with an estimation of gene- and site-specific concordance factors, and the three resulting sets of gene trees were used for separate species-tree analyses with ASTRAL v.5.7.3. Finally, we estimated the phylogeny and the divergence times of notothenioid species with BEAST 2 from a concatenated alignment combining all alignments of the strict set. The original data blocks were grouped in 12 positions selected with the rcluster algorithm of PartitionFinder v.2.1.1, assuming linked branch lengths, equal weights for all model parameters, a minimum partition size of 5,000 bp, and the GTR+Gamma substitution model. The same substitution model was also assumed in the BEAST 2 analysis, together with the birth-death model of diversification and the uncorrelated lognormal relaxed clock model. Time calibration of the phylogeny was based on four age constraints defined according to a recent timeline of teleost evolution inferred from genome and fossil information, at the most recent common ancestors of clades: Eupercaria, around 97.47 MYA (2.5–97.5 inter-percentile range: 91.3–104.0 MYA); the clade combining Eupercaria, Ovalentaria, and Anabantaria – around 101.79 MYA (95.4–109.0 MYA); the clade combining these four groups with Syngnatharia and Pelagiaria – around 104.48 MYA (97.3–112.0 MYA); and the clade combining those six groups with Gobiaria – around 107.08 MYA (100.0–114.0 MYA). All constraints were implemented as lognormal prior distributions with mean values as specified above and a standard deviation between 0.033 and 0.036. Additionally, we constrained the unambiguous monophyly of the groups Notothenioidei, Perciformes, Ovalentaria, Anabantaria, and the clade combining the latter two groups. We performed six replicate BEAST 2 analyses with 330 million MCMC iterations, and convergence among MCMC chains was confirmed by ESS values greater than 120 for all model parameters and greater than 270 for the likelihood and the prior and posterior probabilities. The posterior tree distribution was summarised in the form of a maximum-clade credibility tree with TreeAnnotator v.2.6.0. We attempted to repeat the BEAST 2 analyses with the permissive and full datasets, but these proved too computationally demanding to complete. Nevertheless, the preliminary results from these analyses supported the same tree topology as the analyses with the strict dataset. Numerous novel adaptations characterise the radiation of notothenioids, the dominant fish group in the freezing seas of the Southern Ocean. To improve understanding of the evolution of this iconic fish group, we generated and analysed new genome assemblies for 24 species covering all major subgroups of the radiation, including five long-read assemblies. We present a new estimate for the onset of the radiation at 10.7 million years ago, based on a time-calibrated phylogeny derived from genome-wide sequence data. We identify a two-fold variation in genome size, driven by expansion of multiple transposable element families, and use the long-read data to reconstruct two evolutionarily important, highly repetitive gene family loci. First, we present the most complete reconstruction to date of the antifreeze glycoprotein gene family, whose emergence enabled survival in sub-zero temperatures, showing the expansion of the antifreeze gene locus from the ancestral to the derived state. Second, we trace the loss of haemoglobin genes in icefishes, the only vertebrates lacking functional haemoglobins, through complete reconstruction of the two haemoglobin gene clusters across notothenioid families. Both the haemoglobin and antifreeze genomic loci are characterised by multiple transposon expansions that may have driven the evolutionary history of these genes.

Converging lines of inquiry from across the social and biological sciences target the adult sex ratio (ASR; the proportion of males in the adult population) as a fundamental population-level determinant of behavior. The ASR, which indicates the relative number of potential mates to competitors in a population, frames the selective arena for competition, mate choice, and social interactions. Here we review a growing literature, focusing on methodological developments that sharpen knowledge of the demographic variables underlying ASR variation, experiments that enhance understanding of the consequences of ASR imbalance across societies, and phylogenetic analyses that provide novel insights into social evolution. We additionally highlight areas where research advances are expected to make accelerating contributions across the social sciences, evolutionary biology, and biodiversity conservation. International audience

This paper describes and provides Z1+, the successor of the Z- and Z1-codes for topological analyses of mono- and polydisperse entangled linear polymeric systems, in the presence or absence of confining surfaces or nano-inclusions. In contrast to its predecessors, Z1+ makes use of adaptive neighbor lists, and keeps the number of temporary nodes relatively large, yielding improved performance for large system sizes. Z1+ also includes several features its predecessors lacked, including several that are advantageous for analyses of semi-crystalline systems, brushes, nano-composites, and flowing liquids. It offers a graphical user interface that can be used to run Z1+ and visualize the results, and a PPA+ option that allows Z1+ to perform a primitive path analysis more efficiently than the standard procedure (PPA option). In addition to describing Z1+'s and PPA+'s implementation and computational performance in detail, we use it to show that it yields entanglement lengths that agree quantitatively with both a recently proposed unified analytic theory for flexible and semiflexible polymer-melt entanglement and with the available experimental data for these systems. Finally we show that the associated theoretical expressions, which express reduced entanglement-related quantities in terms of the scaled Kuhn segment density Λ, need not describe results for model polymer solutions of different “chemistries”, i.e. different angular and dihedral interactions but the same Λ. THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOVE

We present an age model for the 651 m deep ice core from Skytrain Ice Rise, situated inland of the Ronne Ice Shelf, Antarctica. The top 2000 years have previously been dated using age markers interpolated through annual layer counting. Below this, we align the Skytrain core to the AICC2012 age model using tie points in the ice and air phase, and we apply the Paleochrono program to obtain the best fit to the tie points and glaciological constraints. In the gas phase, ties are made using methane and, in critical sections, δ18Oair; in the ice phase ties are through 10Be across the Laschamps event and through ice chemistry related to long-range dust transport and deposition. This strategy provides a good outcome to about 108 ka (∼ 605 m). Beyond that there are signs of flow disturbance, with a section of ice probably repeated. Nonetheless values of CH4 and δ18Oair confirm that part of the last interglacial (LIG), from about 117–126 ka (617–627 m), is present and in chronological order. Below this there are clear signs of stratigraphic disturbance, with rapid oscillation of values in both the ice and gas phase at the base of the LIG section, below 628 m. Based on methane values, the warmest part of the LIG and the coldest part of the penultimate glacial are missing from our record. Ice below 631 m appears to be of age > 150 ka. Climate of the Past, 19 (4) ISSN:1814-9332 ISSN:1814-9324

AbstractDespite their role in modulating the marine ecosystem, variability and drivers of low‐oxygen events in the offshore northern Benguela Upwelling System (BenUS) have been rarely investigated due to the events' episodicity which is difficult to resolve using shipboard measurements. We address this issue using 4 months of high‐resolution glider data collected between February and June 2018, 100 km offshore at 18°S. We find that oxygen (O2) concentrations in the offshore northern Benguela are determined by the subsurface alternation of low‐oxygen Angola‐derived water and oxygenated water from the south at 100–500 m depth. We observe intermittent hypoxia (O2 < 60 μmol kg−1) which occurs on average for ∼30% of the 4 months deployment and is driven by the time‐varying subsurface pulses of Angola‐derived tropical water. Hypoxic events are rather persistent at depths of 300–450 m, while they are more sporadic and have weekly duration at shallower depths (100–300 m). We find extreme values of hypoxia, with O2 minima of 16 μmol kg−1, associated with an anticyclonic eddy spinning from the undercurrent flowing on the BenUS shelf and showing no surface signature. Fine‐scale patchiness and water mass mixing are associated with cross‐frontal stirring by a large anticyclone recirculating tropical water into the northern BenUS. The dominance of physical drivers and their high variability on short time scales reveal a dynamic coupling between Angola and Benguela, calling for long‐term and high‐resolution measurements and studies focusing on future changes of both tropical O2 minima and lateral fluxes in this region.

Despite the importance of high-latitude surface energy budgets (SEBs) for land-climate interactions in the rapidly changing Arctic, uncertainties in their prediction persist. Here, we harmonize SEB observations across a network of vegetated and glaciated sites at circumpolar scale (1994-2021). Our variance-partitioning analysis identifies vegetation type as an important predictor for SEB-components during Arctic summer (June-August), compared to other SEB-drivers including climate, latitude and permafrost characteristics. Differences among vegetation types can be of similar magnitude as between vegetation and glacier surfaces and are especially high for summer sensible and latent heat fluxes. The timing of SEB-flux summer-regimes (when daily mean values exceed 0 Wm(-2)) relative to snow-free and -onset dates varies substantially depending on vegetation type, implying vegetation controls on snow-cover and SEB-flux seasonality. Our results indicate complex shifts in surface energy fluxes with land-cover transitions and a lengthening summer season, and highlight the potential for improving future Earth system models via a refined representation of Arctic vegetation types.An international team of researchers finds high potential for improving climate projections by a more comprehensive treatment of largely ignored Arctic vegetation types, underscoring the importance of Arctic energy exchange measuring stations. Peer reviewed