| 1. |
- Shimwell, T. W., et al.
(författare)
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The LOFAR Two-metre Sky Survey: II. First data release
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 622
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Forskningsöversikt (refereegranskat)abstract
- The LOFAR Two-metre Sky Survey (LoTSS) is an ongoing sensitive, high-resolution 120-168 MHz survey of the entire northern sky for which observations are now 20% complete. We present our first full-quality public data release. For this data release 424 square degrees, or 2% of the eventual coverage, in the region of the HETDEX Spring Field (right ascension 10h45m00s to 15h30m00s and declination 45°00′00″ to 57°00′00″) were mapped using a fully automated direction-dependent calibration and imaging pipeline that we developed. A total of 325 694 sources are detected with a signal of at least five times the noise, and the source density is a factor of ∼10 higher than the most sensitive existing very wide-area radio-continuum surveys. The median sensitivity is S144 MHz = 71 μJy beam -1 and the point-source completeness is 90% at an integrated flux density of 0.45 mJy. The resolution of the images is 6″ and the positional accuracy is within 0.2″. This data release consists of a catalogue containing location, flux, and shape estimates together with 58 mosaic images that cover the catalogued area. In this paper we provide an overview of the data release with a focus on the processing of the LOFAR data and the characteristics of the resulting images. In two accompanying papers we provide the radio source associations and deblending and, where possible, the optical identifications of the radio sources together with the photometric redshifts and properties of the host galaxies. These data release papers are published together with a further ∼20 articles that highlight the scientific potential of LoTSS.
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| 2. |
- Bernal, Ximena E., et al.
(författare)
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Empowering Latina scientists
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 363:6429, s. 825-826
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Zhang, Y., et al.
(författare)
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Galaxies in X-ray selected clusters and groups in Dark Energy Survey data - II. Hierarchical Bayesian modelling of the red-sequence galaxy luminosity function
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 488:1, s. 1-17
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Tidskriftsartikel (refereegranskat)abstract
- Using similar to 100 X-ray selected clusters in the Dark Energy Survey Science Verification data, we constrain the luminosity function ( LF) of cluster red-sequence galaxies as a function of redshift. This is the first homogeneous optical/X-ray sample large enough to constrain the evolution of the LF simultaneously in redshift ( 0.1 < z < 1.05) and cluster mass ( 13.5 <= log(10)( M-200crit) similar to< 15.0). We pay particular attention to completeness issues and the detection limit of the galaxy sample. We then apply a hierarchical Bayesian model to fit the cluster galaxy LFs via a Schechter function, including its characteristic break ( m*) to a faint end power-law slope ( alpha). Our method enables us to avoid known issues in similar analyses based on stacking or binning the clusters. We find weak and statistically insignificant (similar to 1.9 sigma) evolution in the faint end slope alpha versus redshift. We also find no dependence in alpha or m* with the X-ray inferred cluster masses. However, the amplitude of the LF as a function of cluster mass is constrained to similar to 20 per cent precision. As a by-product of our algorithm, we utilize the correlation between the LF and cluster mass to provide an improved estimate of the individual cluster masses as well as the scatter in true mass given the X-ray inferred masses. This technique can be applied to a larger sample of X-ray or optically selected clusters from the Dark Energy Survey, significantly improving the sensitivity of the analysis.
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| 4. |
- Loiseau, O., et al.
(författare)
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Targeted Capture of Hundreds of Nuclear Genes Unravels Phylogenetic Relationships of the Diverse Neotropical Palm Tribe Geonomateae
- 2019
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Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- The tribe Geonomateae is a widely distributed group of 103 species of Neotropical palms which contains six ecologically important understory or subcanopy genera. Although it has been the focus of many studies, our understanding of the evolutionary history of this group, and in particular of the taxonomically complex genus Geonoma, is far from complete due to a lack of molecular data. Specifically, the previous Sanger sequencing-based studies used a few informative characters and partial sampling. To overcome these limitations, we used a recently developed Arecaceae-specific target capture bait set to undertake a phylogenomic analysis of the tribe Geonomateae. We sequenced 3,988 genomic regions for 85% of the species of the tribe, including 84% of the species of the largest genus, Geonoma. Phylogenetic relationships were inferred using both concatenation and coalescent methods. Overall, our phylogenetic tree is highly supported and congruent with taxonomic delimitations although several morphological taxa were revealed to be non-monophyletic. It is the first time that such a large genomic dataset is provided for an entire tribe within the Arecaceae. Our study lays the groundwork not only for detailed macro- and micro-evolutionary studies within the group, but also sets a workflow for understanding other species complexes across the tree of life.
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| 5. |
- Soranno, Patricia A., et al.
(författare)
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LAGOS-NE : A multi-scaled geospatial and temporal database of lake ecological context and water quality for thousands of U.S. lakes
- 2017
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Ingår i: GigaScience. - : Oxford University Press (OUP). - 2047-217X. ; 6:12, s. 1-22
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the factors that affect water quality and the ecological services provided by freshwater ecosystems is an urgent global environmental issue. Predicting how water quality will respond to global changes not only requires water quality data, but also information about the ecological context of individual water bodies across broad spatial extents. Because lake water quality is usually sampled in limited geographic regions, often for limited time periods, assessing the environmental controls of water quality requires compilation of many data sets across broad regions and across time into an integrated database. LAGOS-NE accomplishes this goal for lakes in the northeastern-most 17 US states. LAGOS-NE contains data for 51101 lakes and reservoirs larger than 4 ha in 17 lake-rich US states. The database includes 3 datamodules for: lake location and physical characteristics for all lakes; ecological context (i.e., the land use, geologic, climatic, and hydrologic setting of lakes) for all lakes; and in situmeasurements of lake water quality for a subset of the lakes fromthe past 3 decades for approximately 2600–12 000 lakes depending on the variable. The database contains approximately 150000 measures of total phosphorus, 200 000 measures of chlorophyll, and 900 000 measures of Secchi depth. The water quality data were compiled from87 lake water quality data sets fromfederal, state, tribal, and non-profit agencies, university researchers, and citizen scientists. This database is one of the largest andmost comprehensive databases of its type because it includes both in situmeasurements and ecological context data. Because ecological context can be used to study a variety of other questions about lakes, streams, and wetlands, this database can also be used as the foundation for other studies of freshwaters at broad spatial and ecological scales
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| 6. |
- Amendola, L., et al.
(författare)
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Cosmology and fundamental physics with the Euclid satellite
- 2018
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Ingår i: Living Reviews in Relativity. - : Springer. - 1433-8351 .- 2367-3613. ; 21:1
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Tidskriftsartikel (refereegranskat)abstract
- Euclid is a European Space Agency medium-class mission selected for launch in 2020 within the cosmic vision 2015–2025 program. The main goal of Euclid is to understand the origin of the accelerated expansion of the universe. Euclid will explore the expansion history of the universe and the evolution of cosmic structures by measuring shapes and red-shifts of galaxies as well as the distribution of clusters of galaxies over a large fraction of the sky. Although the main driver for Euclid is the nature of dark energy, Euclid science covers a vast range of topics, from cosmology to galaxy evolution to planetary research. In this review we focus on cosmology and fundamental physics, with a strong emphasis on science beyond the current standard models. We discuss five broad topics: dark energy and modified gravity, dark matter, initial conditions, basic assumptions and questions of methodology in the data analysis. This review has been planned and carried out within Euclid’s Theory Working Group and is meant to provide a guide to the scientific themes that will underlie the activity of the group during the preparation of the Euclid mission.
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| 7. |
- Wisotzki, L., et al.
(författare)
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Nearly all the sky is covered by Lyman-alpha emission around high-redshift galaxies
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 562:7726, s. 229-232
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Tidskriftsartikel (refereegranskat)abstract
- Galaxies are surrounded by large reservoirs of gas, mostly hydrogen, that are fed by inflows from the intergalactic medium and by outflows from galactic winds. Absorption-line measurements along the lines of sight to bright and rare background quasars indicate that this circumgalactic medium extends far beyond the starlight seen in galaxies, but very little is known about its spatial distribution. The Lyman-alpha transition of atomic hydrogen at a wavelength of 121.6 nanometres is an important tracer of warm (about 104 kelvin) gas in and around galaxies, especially at cosmological redshifts greater than about 1.6 at which the spectral line becomes observable from the ground. Tracing cosmic hydrogen through its Lyman-a emission has been a long-standing goal of observational astrophysics(1-3), but the extremely low surface brightness of the spatially extended emission is a formidable obstacle. A new window into circumgalactic environments was recently opened by the discovery of ubiquitous extended Lyman-alpha emission from hydrogen around high-redshift galaxies(4,5). Such measurements were previously limited to especially favourable systems(6-8) or to the use of massive statistical averaging(9,10) because of the faintness of this emission. Here we report observations of low-surface-brightness Lyman-alpha emission surrounding faint galaxies at redshifts between 3 and 6. We find that the projected sky coverage approaches 100 per cent. The corresponding rate of incidence (the mean number of Lyman-alpha emitters penetrated by any arbitrary line of sight) is well above unity and similar to the incidence rate of high-column-density absorbers frequently detected in the spectra of distant quasars(11-14). This similarity suggests that most circumgalactic atomic hydrogen at these redshifts has now been detected in emission.
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| 8. |
- Kehoe, Laura, et al.
(författare)
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Make EU trade with Brazil sustainable
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Urrutia, T., et al.
(författare)
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The MUSE-Wide Survey : survey description and first data release
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 624
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Tidskriftsartikel (refereegranskat)abstract
- We present the MUSE-Wide survey, a blind, 3D spectroscopic survey in the CANDELS/GOODS-S and CANDELS/COSMOS regions. The final survey will cover 100 x 1 arcmin(2) MUSE fields. Each MUSE-Wide pointing has a depth of one hour and hence targets more extreme and more luminous objects over ten times the area of the MUSE-Deep fields. The legacy value of MUSE-Wide lies in providing spectroscopy of everything without photometric pre-selection. We describe the data reduction, post-processing and PSF characterization of the first 44 CANDELS /GOODS-S MUSE-Wide pointings released with this publication. Using a 3D matched filtering approach we detect 1602 emission line sources, including 479 Lyman-alpha (Ly alpha) emitting galaxies with redshifts 2.9 less than or similar to z less than or similar to 6.3. We cross-matched the emission line sources to existing photometric catalogs, finding almost complete agreement in redshifts (photometric and spectroscopic) and stellar masses for our low redshift (z < 1.5) emitters. At high redshift, we only find similar to 55% matches to photometric catalogs. We encounter a higher outlier rate and a systematic offset of Delta z similar or equal to 0.2 when comparing our MUSE redshifts with photometric redshifts from the literature. Cross-matching the emission line sources with X-ray catalogs from the Chandra Deep Field South, we find 127 matches, mostly in agreement with the literature redshifts, including ten objects with no prior spectroscopic identification. Stacking X-ray images centered on our Ly alpha emitters yields no signal; the Ly alpha population is not dominated by even low luminosity AGN. Other cross-matches of our emission-line catalog to radio and submillimeter data, yielded far lower numbers of matches, most of which already were covered by the X-ray catalog. A total of 9205 photometrically selected objects from the CANDELS survey lie in the MUSE-Wide footprint, of which we provide optimally extracted 1D spectra. We are able to determine the spectroscopic redshift of 98% of 772 photometrically selected galaxies brighter than 24th F775W magnitude. All the data in the first data release - datacubes, catalogs, extracted spectra, maps - are available on the MUSE-Wide data release webpage.
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| 10. |
- Sander, N. L., et al.
(författare)
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Rivers shape population genetic structure in Mauritia flexuosa (Arecaceae)
- 2018
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 8:13, s. 6589-6598
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Tidskriftsartikel (refereegranskat)abstract
- The Mauritia flexuosa L.f. palm is known as the tree of life given its importance as fundamental food and construction resources for humans. The species is broadly distributed in wet habitats of Amazonia and dry habitats of the Amazon and Orinoco river basins and in the Cerrado savanna. We collected 179 individuals from eight different localities throughout these habitats and used microsatellites to characterize their population structure and patterns of gene flow. Overall, we found high genetic variation, except in one savanna locality. Gene flow between populations is largely congruent with river basins and the direction of water flow within and among them, suggesting their importance for seed dispersal. Further, rivers have had a higher frequency of human settlements than forested sites, contributing to population diversity and structure through increased human use and consumption of M.flexuosa along rivers. Gene flow patterns revealed that migrants are sourced primarily from within the same river basin, such as those from Madeira and Tapajos basins. Our work suggests that rivers and their inhabitants are a critical element of the landscape in Amazonia and have impacted the dispersal and subsequent distribution of tropical palm species, as shown by the patterns of genetic variation in M.flexuosa.
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| 11. |
- Bacon, Christine D., et al.
(författare)
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Biogeography of the Malagasy Celastraceae: Multiple independent origins followed by widespread dispersal of genera from Madagascar
- 2016
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Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903 .- 1095-9513. ; 94, s. 365-382
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Tidskriftsartikel (refereegranskat)abstract
- © 2015 Elsevier Inc.. Of the 97 currently recognized genera of Celastraceae, 19 are native to Madagascar, including six endemics. In this study we conducted the most thorough phylogenetic analysis of Celastraceae yet completed with respect to both character and taxon sampling, and include representatives of five new endemic genera. Fifty-one new accessions, together with 328 previously used accessions of Celastrales, were sampled for morphological characters, two rDNA gene regions, and two plastid gene regions. The endemic Malagasy genera are resolved in two separate lineages- Xenodrys by itself and all other endemic genera in a clade that also includes four lineages inferred to have dispersed from Madagascar: Brexia madagascariensis (Mascarene Islands, coastal Africa), Elaeodendron (West Indies, Africa to New Caledonia), and Pleurostylia (Africa to New Caledonia). Of the 12 extant Malagasy Celastraceae lineages identified, eight are clearly of African origin. The origins of the remaining four lineages are less clear, but reasonable possibilities include America, Eurasia, Africa, southern India, Malesia, and Australia. Based on 95% credible age intervals from fossil-calibrated molecular dating, all 12 extant Malagasy Celastraceae lineages appear to have arisen following dispersal after the separation of Madagascar from other landmasses within the last 70. million years.
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| 12. |
- Cano, A., et al.
(författare)
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The roles of dispersal and mass extinction in shaping palm diversity across the Caribbean
- 2018
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Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270. ; 45:6, s. 1432-1443
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Tidskriftsartikel (refereegranskat)abstract
- Aim: The rich flora of the Caribbean islands and surrounding mainland evolved in a context of isolation alternated with phases of terrestrial connectivity between landmasses, climatic fluctuations and episodes of mass extinctions during the Cenozoic. We explored how these events affected the evolution of the sister palm tribes Cryosophileae and Sabaleae, and how continent-island exchanges, endemic radiations and mass extinction shaped their extant diversity. Methods: We reconstructed a time-calibrated phylogeny of the palm tribes Cryosophileae and Sabaleae using 84% of the known species. We inferred ancestral distribution and tested the effect of island colonization and mass extinction on extant diversity. Results: Our results indicate that Cryosophileae and Sabaleae originated c. 77 Ma most probably in Laurasia, and their extant species started to diversify between 5635 Ma and 19-10 Ma respectively. Biogeographical state reconstruction estimated that Cryosophileae dispersed to South America between 56-35 Ma, then dispersed to North-Central America between 39-25 Ma and the Caribbean islands between 3421 Ma. We detected a possible signature of a mass extinction event at the end of the Eocene, affecting the diversification of Cryosophileae and Sabaleae and we did not detect a diversification rate shift related to the colonization of the Caribbean islands. Main conclusions: Species of Cryosophileae in the Caribbean islands are probably derived from a single Oligocene dispersal event that likely occurred overwater from North-Central America rather than through the hypothesized GAARlandia land bridge. Contrastingly, three independent Miocene dispersal events from North-Central America explain the occurrence of Sabaleae in the Caribbean islands. Contrary to our expectations, island colonization did not trigger increased diversification. Instead, we find that diversification patterns in this clade, and its disappearance from northernmost latitudes, could be the signature of a mass extinction triggered by the global temperature decline at the end of the Eocene.
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| 13. |
- Bacon, Christine D., et al.
(författare)
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Endemic palm species shed light on habitat shifts and the assembly of the Cerrado and Restinga floras
- 2017
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Ingår i: Molecular Phylogenetics and Evolution. - : Elsevier BV. - 1055-7903. ; 110, s. 127-133
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Tidskriftsartikel (refereegranskat)abstract
- Species expansions into new habitats are often associated with physiological adaptations, for instance when rain forest lineages colonize dry habitats. Although such shifts have been documented for the Brazilian savanna (Cerrado), little is known about the biogeographic origin of species occupying an extreme South American habitat type, the coastal dunes (Restinga). We examined the formation of this poorly known, endangered habitat by reconstructing the evolutionary history of two endemic species. Due to the proposed recency and uniqueness of this habitat, we hypothesized that Restinga species of the palm genus Allagoptera to be recently evolved and to present derived morphological characters. To detect habit shifts in absolute time, we used one plastid and nine nuclear genes to reconstruct the phylogenetic and biogeographic history of Allagoptera. We used light microscopy and stable isotope analysis to explore whether morphological adaptations occurred concomitantly with habitat shifts. Phylogenetic relationships were well supported and we found ancestral lineages of Allagoptera to be widely distributed throughout habitats that are currently occupied by extant species. Over the last ca. 7 Ma Allagoptera has shifted its preference to increasingly dry habitats. Coincident with the colonization of the Cerrado and Restinga, morphological adaptations also evolved, including subterranean stems that are fire-resistant and long underground stem and root systems that facilitate water access. We did not find differences in metabolic pathway or modifications to pollen morphology when compared to other palm lineages. Assuming that the evolutionary history of Allagoptera is indicative of the habitat in which it occurs, our results infer a recent origin for Cerrado species. Although little is known about the formation of the Restinga habitat, our results also suggest a longer history than currently proposed; with an origin of Restinga habitats dating back to the Late Pliocene. (C) 2017 Elsevier Inc. All rights reserved.
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| 14. |
- Bacon, Christine D., et al.
(författare)
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Evolutionary persistence in Gunnera and the contribution of southern plant groups to the tropical Andes biodiversity hotspot
- 2018
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Ingår i: PeerJ. - : PeerJ. - 2167-8359. ; 2018:3
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Tidskriftsartikel (refereegranskat)abstract
- Several studies have demonstrated the contribution of northern immigrants to the flora of the tropical Andesthe world's richest and most diverse biodiversity hotspot. However, much less is known about the biogeographic history and diversification of Andean groups with southern origins, although it has been suggested that northern and southern groups have contributed roughly equally to the high Andean (i.e., páramo) flora. Here we infer the evolutionary history of the southern hemisphere plant genus Gunnera, a lineage with a rich fossil history and an important ecological role as an early colonising species characteristic of wet, montane environments. Our results show striking contrasts in species diversification, where some species may have persisted for some 90 million years, and whereas others date to less than 2 Ma since origination. The outstanding longevity of the group is likely linked to a high degree of niche conservatism across its highly disjunct range, whereby Gunnera tracks damp and boggy soils in cool habitats. Colonisation of the northern Andes is related to Quaternary climate change, with subsequent rapid diversification appearing to be driven by their ability to take advantage of environmental opportunities. This study demonstrates the composite origin of a mega-diverse biota.
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| 15. |
- Bacon, Christine D., et al.
(författare)
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Quaternary glaciation and the Great American Biotic Interchange
- 2016
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Ingår i: Geology. - : Geological Society of America. - 0091-7613 .- 1943-2682. ; 44:5, s. 375-378
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Tidskriftsartikel (refereegranskat)abstract
- Recent geological studies demonstrate that the Isthmus of Panama emerged some 10 m.y. earlier than previously assumed. Although absent today in Panama, Central American savanna environments likely developed in connection with the onset of Northern Hemisphere glaciations. As is widely recognized, most of the mammals crossing the isthmus since 2.5 Ma lived in savannas. Could climate-induced vegetational changes across Panama explain the delayed migration of mammals, rather than terrestrial connectivity? We investigate the congruence between cross-continental mammal migration and climate change through analysis of fossil data and molecular phylogenies. Evidence from fossil findings shows that the vast majority of mammals crossed between South and North America after ca. 3 Ma. By contrast, dated mammal phylogenies suggest that migration events started somewhat earlier, ca. 4-3 Ma, but allowing for biases toward greater ages of molecular than geologic dating and uncertainties in the former, we consider this age range not to be significantly earlier than 3 Ma. We conclude that savanna-like environments developed in response to the vast Laurentide ice sheet at the first Quaternary glaciation triggered the initiation of the Great American Biotic Interchange in mammals.
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| 16. |
- Bacon, Christine D., et al.
(författare)
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Soil fertility and flood regime are correlated with phylogenetic structure of Amazonian palm communities
- 2019
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Ingår i: Annals of Botany. - : Oxford University Press (OUP). - 0305-7364 .- 1095-8290. ; 123:4, s. 641-655
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Tidskriftsartikel (refereegranskat)abstract
- Background and Aims Identifying the processes that generate and maintain biodiversity requires understanding of how evolutionary processes interact with abiotic conditions to structure communities. Edaphic gradients are strongly associated with floristic patterns but, compared with climatic gradients, have received relatively little attention. We asked (1) How does the phylogenetic composition of palm communities vary along edaphic gradients within major habitat types? and (2) To what extent are phylogenetic patterns determined by (a) habitat specialists, (b) small versus large palms, and (c) hyperdiverse genera? Methods We paired data on palm community composition from 501 transects of 0.25 ha located in two main habitat types (non-inundated uplands and seasonally inundated floodplains) in western Amazonian rain forests with information on soil chemistry, climate, phylogeny and metrics of plant size. We focused on exchangeable base concentration (cmol(+) kg(-1)) as a metric of soil fertility and a floristic index of inundation intensity. We used a null model approach to quantify the standard effect size of mean phylogenetic distance for each transect (a metric of phylogenetic community composition) and related this value to edaphic variables using generalized linear mixed models, including a term for spatial autocorrelation. Key Results Overall, we recorded 112 008 individuals belonging to 110 species. Palm communities in non-inundated upland transects (but not floodplain transects) were more phylogenetically clustered in areas of low soil fertility, measured as exchangeable base concentration. In contrast, floodplain transects with more severe flood regimes (as inferred from floristic structure) tended to be phylogenetically clustered. Nearly half of the species recorded (44 %) were upland specialists while 18 % were floodplain specialists. In both habitat types, phylogenetic clustering was largely due to the co-occurrence of small-sized habitat specialists belonging to two hyperdiverse genera (Bactris and Geonoma). Conclusions Edaphic conditions are associated with the phylogenetic community structure of palms across western Amazonia, and different factors (specifically, soil fertility and inundation intensity) appear to underlie diversity patterns in non-inundated upland versus floodplain habitats. By linking edaphic gradients with palm community phylogenetic structure, our study reinforces the need to integrate edaphic conditions in eco-evolutionary studies in order to better understand the processes that generate and maintain tropical forest diversity. Our results suggest a role for edaphic niche conservatism in the evolution and distribution of Amazonian palms, a finding with potential relevance for other clades.
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| 17. |
- Barrett, C. F., et al.
(författare)
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Ancient Polyploidy and Genome Evolution in Palms
- 2019
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Ingår i: Genome Biology and Evolution. - : Oxford University Press (OUP). - 1759-6653. ; 11:5, s. 1501-1511
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Tidskriftsartikel (refereegranskat)abstract
- Mechanisms of genome evolution are fundamental to our understanding of adaptation and the generation and maintenance of biodiversity, yet genome dynamics are still poorly characterized in many clades. Strong correlations between variation in genomic attributes and species diversity across the plant tree of life suggest that polyploidy or other mechanisms of genome size change confer selective advantages due to the introduction of genomic novelty. Palms (order Arecales, family Arecaceae) are diverse, widespread, and dominant in tropical ecosystems, yet little is known about genome evolution in this ecologically and economically important clade. Here, we take a phylogenetic comparative approach to investigate palm genome dynamics using genomic and transcriptomic data in combination with a recent, densely sampled, phylogenetic tree. We find conclusive evidence of a paleopolyploid event shared by the ancestor of palms but not with the sister clade, Dasypogonales. We find evidence of incremental chromosome number change in the palms as opposed to one of recurrent polyploidy. We find strong phylogenetic signal in chromosome number, but no signal in genome size, and further no correlation between the two when correcting for phylogenetic relationships. Palms thus add to a growing number of diverse, ecologically successful clades with evidence of whole-genome duplication, sister to a species-poor clade with no evidence of such an event. Disentangling the causes of genome size variation in palms moves us closer to understanding the genomic conditions facilitating adaptive radiation and ecological dominance in an evolutionarily successful, emblematic tropical clade.
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| 18. |
- Bernal, R., et al.
(författare)
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- Could coastal plants in western Amazonia be relicts of past marine incursions?
- 2019
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Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 46:8, s. 1749-1759
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Tidskriftsartikel (refereegranskat)abstract
- - The rainforests of Amazonia comprise some of the most biologically diverse ecosystems on Earth. Despite this high biodiversity, little is known about how landscape changes that took place in deep history have affected the assembly of its species, and whether the impact of such changes on biodiversity can still be observed. Here, we present a hypothesis to explain our observation that plants typical of Neotropical coastal habitats also occur in western Amazonia, in some cases thousands of kilometres away from the coast. Evidence on their current distribution, dispersal biology and divergence times estimated from molecular phylogenies suggest that these plants may be the legacy of the large marine-influenced embayment that dominated the area for millions of years in the Neogene. We hypothesize that coastal plants dispersed along the shores of this embayment and persisted as inland relicts after the marine incursion(s) retreated, probably with the aid of changes in soil conditions caused by the deposition of marine sediments. This dispersal corridor may also have facilitated the colonization of coastal environments by Amazonian lineages. These scenarios could imply an unexpected coastal source that has contributed to Amazonia's high floristic diversity and led to disjunct distributions across the Neotropics. We highlight the need for future studies and additional evidence to validate and shed further light on this potentially important pattern. © 2019 John Wiley & Sons Ltd
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| 19. |
- Cássia-Silva, C., et al.
(författare)
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Niche conservatism drives a global discrepancy in palm species richness between seasonally dry and moist habitats
- 2019
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Ingår i: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 28:6, s. 814-825
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Rapid global environmental change predicts increasingly seasonal climate in the tropics, causing expansion of seasonally dry habitats and leading to shifts in species distribution and potential extinction. Here, we use a macroevolutionary framework to understand the processes driving palm diversity patterns between moist and seasonally dry tropical habitats. We hypothesize that the discrepancy in species richness between habitats is explained by higher speciation rates in moist habitat and that niche conservatism prevents frequent shifts between habitats. Location: Global. Time period: Last 100Ma. Major taxa studied: Arecaceae. Methods: We used trait-dependent diversification models to test whether different habitats affect palm speciation rates. Furthermore, palm assemblages were divided into three regions (Africa, Australasia and Neotropics) to test for niche conservatism and evaluate phylogenetic dissimilarity. Results: We found no relationship between speciation rate and habitat type. We detected phylogenetic signal for habitats at both global and continental scales, indicating that closely related species were more similar than expected by chance. Colonization of seasonally dry habitats occurred c.60Ma, yet most clades only diversified after c.30Ma. The high phylogenetic dissimilarity between habitat types at both global and continental scales was driven by high lineage turnover, at least for Africa and the Neotropics. Main conclusions: We found a lack of differential speciation rates in setting the seasonally dry and moist palm-richness discrepancy. However, over evolutionary history most palm lineages fail to colonize seasonally dry habitats owing to a tendency to retain ancestral habitat. Indeed, seasonally dry palm assemblages are the result of the diversification of particular lineages. Likewise, long-term dry periods appear to induce shifts in taxonomic and functional diversity, and we emphasize that the expansion of dry habitats might also imply a loss of palm clades, hence a reduction in phylogenetic diversity. © 2019 John Wiley & Sons Ltd
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| 20. |
- Diener, C., et al.
(författare)
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The MUSE-Wide survey : detection of a clustering signal from Lyman alpha emitters in the range 3 < z < 6
- 2017
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 471:3, s. 3186-3192
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Tidskriftsartikel (refereegranskat)abstract
- We present a clustering analysis of a sample of 238 Ly alpha emitters at redshift 3 less than or similar to z less than or similar to 6 from the MUSE-Wide survey. This survey mosaics extragalactic legacy fields with 1h MUSE pointings to detect statistically relevant samples of emission line galaxies. We analysed the first year observations from MUSE-Wide making use of the clustering signal in the line-of-sight direction. This method relies on comparing pair-counts at close redshifts for a fixed transverse distance and thus exploits the full potential of the redshift range covered by our sample. A clear clustering signal with a correlation length of r(0) = 2.9(-1.1)(+1.0) Mpc (comoving) is detected. Whilst this result is based on only about a quarter of the full survey size, it already shows the immense potential of MUSE for efficiently observing and studying the clustering of Ly alpha emitters.
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| 21. |
- Dotto, T. S., et al.
(författare)
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Wind-Driven Processes Controlling Oceanic Heat Delivery to the Amundsen Sea, Antarctica
- 2019
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Ingår i: Journal of Physical Oceanography. - : American Meteorological Society. - 0022-3670 .- 1520-0485. ; 49:11, s. 2829-2849
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Tidskriftsartikel (refereegranskat)abstract
- Variability in the heat delivery by Circumpolar Deep Water (CDW) is responsible for modulating the basal melting of the Amundsen Sea ice shelves. However, the mechanisms controlling the CDW inflow to the region's continental shelf remain little understood. Here, a high-resolution regional model is used to assess the processes governing heat delivery to the Amundsen Sea. The key mechanisms are identified by decomposing CDW temperature variability into two components associated with 1) changes in the depth of isopycnals [heave (HVE)], and 2) changes in the temperature of isopycnals [water mass property changes (WMP)]. In the Dotson-Getz trough, CDW temperature variability is primarily associated with WMP. The deeper thermocline and shallower shelf break hinder CDW access to that trough, and CDW inflow is regulated by the uplift of isopycnals at the shelf break-which is itself controlled by wind-driven variations in the speed of an undercurrent flowing eastward along the continental slope. In contrast, CDW temperature variability in the Pine Island-Thwaites trough is mainly linked to HVE. The shallower thermocline and deeper shelf break there permit CDW to persistently access the continental shelf. CDW temperature in the area responds to wind-driven modulation of the water mass on-shelf volume by changes in the rate of inflow across the shelf break and in Ekman pumping-induced vertical displacement of isopycnals within the shelf. The western and eastern Amundsen Sea thus represent distinct regimes, in which wind forcing governs CDW-mediated heat delivery via different dynamics.
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| 22. |
- Drake, A. B., et al.
(författare)
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The MUSE Hubble Ultra Deep Field Survey VI. The faint-end of the Lyα luminosity function at 2.91
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 608
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Tidskriftsartikel (refereegranskat)abstract
- We present the deepest study to date of the Ly alpha luminosity function in a blank field using blind integral field spectroscopy from MUSE. We constructed a sample of 604 Ly alpha emitters (LAEs) across the redshift range 2.91 < z < 6.64 using automatic detection software in the Hubble Ultra Deep Lield. The deep data cubes allowed us to calculate accurate total Ly alpha fluxes capturing low surface-brightness extended Ly alpha emission now known to be a generic property of high-redshift star-forming galaxies. We simulated realistic extended LAEs to fully characterise the selection function of our samples, and performed flux-recovery experiments to test and correct for bias in our determination of total Ly alpha fluxes. We find that an accurate completeness correction accounting for extended emission reveals a very steep faint-end slope of the luminosity function, alpha, down to luminosities of log(10) L erg s(-1) < 41.5, applying both the 1/V-max and maximum likelihood estimators. Splitting the sample into three broad redshift bins, we see the faint-end slope increasing from -2.03(-0.07)(+1.42) at z approximate to 3.44 to -2.86(-infinity)(+0.76) Z approximate to 76 at z approximate to 5.48, however no strong evolution is seen between the 68% confidence regions in L*-alpha parameter space. Using the Ly alpha line flux as a proxy for star formation activity, and integrating the observed luminosity functions, we find that LAEs' contribution to the cosmic star formation rate density rises with redshift until it is comparable to that from continuum-selected samples by z approximate to 6. This implies that LAEs may contribute more to the star-formation activity of the early Universe than previously thought, as any additional intergalactic medium (IGM) correction would act to further boost the Ly alpha luminosities. Linally, assuming fiducial values for the escape of Ly alpha and LyC radiation, and the dumpiness of the IGM, we integrated the maximum likelihood luminosity function at 5.00 < z < 6.64 and find we require only a small extrapolation beyond the data (<1 dex in luminosity) for LAEs alone to maintain an ionised IGM at z approximate to 6.
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| 23. |
- Gullberg, B., et al.
(författare)
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The mysterious morphology of MRC0943-242 as revealed by ALMA and MUSE
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 586
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 ESO. We present a pilot study of the z = 2.923 radio galaxy MRC0943-242, where we combine information from ALMA and MUSE data cubes for the first time. Even with modest integration times, we disentangle the AGN and starburst dominated components. These data reveal a highly complex morphology as the AGN, starburst, and molecular gas components show up as widely separated sources in dust continuum, optical continuum, and CO line emission observations. CO(1-0) and CO(8-7) line emission suggest that there is a molecular gas reservoir offset from both the dust and the optical continuum that is located ∼90 kpc from the AGN. The UV line emission has a complex structure in emission and absorption. The line emission is mostly due to a large scale ionisation cone energised by the AGN, and a Lyα emitting bridge of gas between the radio galaxy and a heavily star-forming set of components. Strangely, the ionisation cone has no Lyα emission. We find this is due to an optically thick layer of neutral gas with unity covering fraction spread out over a region of at least ∼100 kpc from the AGN. Other less thick absorption components are associated with Lyα emitting gas within a few tens of kpc from the radio galaxy and are connected by a bridge of emission. We speculate that this linear structure of dust, Lyα and CO emission, and the redshifted absorption seen in the circum nuclear region may represent an accretion flow feeding gas into this massive AGN host galaxy.
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| 24. |
- Hashimoto, T., et al.
(författare)
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The MUSE Hubble Ultra Deep Field Survey X. Ly alpha equivalent widths at 2.9 < z < 6.6
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 608
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Tidskriftsartikel (refereegranskat)abstract
- We present rest-frame Ly alpha equivalent widths (EW0) of 417 Ly alpha emitters (LAEs) detected with Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT) at 2.9 < z < 6.6 in the Hubble Ultra Deep Field. Based on the deep MUSE spectroscopy and ancillary Hubble Space Telescope (HST) photometry data, we carefully measured EW0 values taking into account extended Ly alpha emission and UV continuum slopes (beta). Our LAEs reach unprecedented depths, both in Ly alpha luminosities and UV absolute magnitudes, from log (L-Ly alpha/erg s(-1)) similar to 41.0 to 43.0 and from M-UV similar to -16 to -21 (0.01-1.0 L-z=3(*)). The EW0 values span the range of similar to 5 to 240 angstrom or larger, and their distribution can be well fitted by an exponential law N = N-0 exp(-EW0/w(0)). Owing to the high dynamic range in M-UV, we find that the scale factor, w(0), depends on M-UV in the sense that including fainter M-UV objects increases w(0), i.e., the Ando effect. The results indicate that selection functions affect the EW0 scale factor. Taking these effects into account, we find that our w(0) values are consistent with those in the literature within 1 sigma uncertainties at 2.9 < z < 6.6 at a given threshold of M-UV and LLy alpha. Interestingly, we find 12 objects with EW0> 200 angstrom above 1 sigma uncertainties. Two of these 12 LAEs show signatures of merger or AGN activity: the weak Civ lambda 1549 emission line. For the remaining 10 very large EW0 LAEs, we find that the EW0 values can be reproduced by young stellar ages (< 100 Myr) and low metallicities (less than or similar to 0.02 Z(circle dot)). Otherwise, at least part of the Ly alpha emission in these LAEs needs to arise from anisotropic radiative transfer effects, fluorescence by hidden AGN or quasi-stellar object activity, or gravitational cooling.
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| 25. |
- Herenz, Edmund Christian, et al.
(författare)
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The MUSE-Wide survey : A first catalogue of 831 emission line galaxies
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 606
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Tidskriftsartikel (refereegranskat)abstract
- We present a first instalment of the MUSE-Wide survey, covering an area of 22.2 arcmin(2) (corresponding to similar to 20% of the final survey) in the CANDELS /Deep area of the Chandra Deep Field South. We use the MUSE integral field spectrograph at the ESO VLT to conduct a full-area spectroscopic mapping at a depth of 1 h exposure time per 1 arcmin(2) pointing. We searched for compact emission line objects using our newly developed LSDCat software based on a 3D matched filtering approach, followed by interactive classification and redshift measurement of the sources. Our catalogue contains 831 distinct emission line galaxies with redshifts ranging from 0.04 to 6. Roughly one third (237) of the emission line sources are Lyman alpha emitting galaxies with 3 < z < 6, only four of which had previously measured spectroscopic redshifts. At lower redshifts 351 galaxies are detected primarily by their [O i i] emission line (0.3 <= z <= 1.5), 189 by their [OIII] line (0.21 <= z <= 0.85), and 46 by their H alpha line (0.04 <= z <= 0.42). Comparing our spectroscopic redshifts to photometric redshift estimates from the literature, we find excellent agreement for z < 1.5 with a median Delta(z) of only similar to 4 x 10(-4) and an outlier rate of 6%, however a significant systematic offset of Delta(z) = 0.26 and an outlier rate of 23% for Ly alpha emitters at z > 3. Together with the catalogue we also release 1D PSF-weighted extracted spectra and small 3D datacubes centred on each of the 831 sources.
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| 26. |
- Sanín, M. J., et al.
(författare)
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The Neogene rise of the tropical Andes facilitated diversification of wax palms (Ceroxylon: Arecaceae) through geographical colonization and climatic niche separation
- 2016
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Ingår i: Botanical journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4074 .- 1095-8339. ; 182:2, s. 303-317
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Tidskriftsartikel (refereegranskat)abstract
- The tropical Andes are a biodiversity hotspot, partly due to their rich and complex floristic composition. A fundamental question regarding this outstanding biodiversity is what role the Andean orogeny has played in species diversification. Ceroxylon is a genus of endemic Andean palms that stands out in the palm family (Arecaceae) due to its adaptation to cold, mountainous environments. Here, we reconstruct the biogeography and climatic preference of this lineage to test the hypothesis that Andean uplift allowed diversification by providing suitable habitats along climatic and elevational gradients. Ancestral areas were reconstructed under a model allowing for founder-event speciation and climatic niches were inferred from climatic variables at present-day occurrences of all species. Niche evolution in a phylogenetic framework was evaluated by testing differences between the climatic niches of clades. Our analyses identified four main clades, with a general pattern of diversification through geographical colonization from south to north after the Pliocene uplift of the northern Andes. Adaptation to low temperatures was conserved at the generic level, with climatic niche differentiation among clades along elevational temperature gradients. We conclude that the Neogene Andean uplift has facilitated the diversification of this iconic plant group via opportunities for geographical migration and separation within its climatic niche. © 2016 The Linnean Society of London
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| 27. |
- Verhamme, A., et al.
(författare)
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Recovering the systemic redshift of galaxies from their Lyman alpha line profile
- 2018
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966 .- 1745-3925 .- 1745-3933. ; 478:1, s. L60-L65
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Tidskriftsartikel (refereegranskat)abstract
- The Lyman alpha (Ly alpha) line of Hydrogen is a prominent feature in the spectra of star-forming galaxies, usually redshifted by a few hundreds of km s(-1) compared to the systemic redshift. This large offset hampers follow-up surveys, galaxy pair statistics, and correlations with quasar absorption lines when only Ly alpha is available. We propose diagnostics that can be used to recover the systemic redshift directly from the properties of the Ly alpha line profile. We use spectroscopic observations of Ly alpha emitters for which a precise measurement of the systemic redshift is available. Our sample contains 13 sources detected between z approximate to 3 and z approximate to 6 as part of various multi-unit spectroscopic explorer guaranteed time observations. We also include a compilation of spectroscopic Ly alpha data from the literature spanning a wide redshift range (z approximate to 0-8). First, restricting our analysis to double-peaked Ly alpha spectra, we find a tight correlation between the velocity offset of the red peak with respect to the systemic redshift, V-peak(red), and the separation of the peaks. Secondly, we find a correlation between V-peak(red) and the full width at half-maximum of the Ly alpha line. Fitting formulas to estimate systemic redshifts of galaxies with an accuracy of <= 100 km s(-1), when only the Ly alpha emission line is available, are given for the two methods.
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| 28. |
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