108 research outputs found
A new classification of Cyperaceae (Poales) supported by phylogenomic data
Cyperaceae (sedges) are the third largest monocot family and are of considerable economic and ecological importance. Sedges represent an ideal model family to study evolutionary biology because of their species richness, global distribution, large discrepancies in lineage diversity, broad range of ecological preferences, and adaptations including multiple origins of C4 photosynthesis and holocentric chromosomes. Goetghebeurâs seminal work on Cyperaceae published in 1998 provided the most recent complete classification at tribal and generic level, based on a morphological study of Cyperaceae inflorescence, spikelet, flower and embryo characters plus anatomical and other information. Since then, several familyâlevel molecular phylogenetic studies using Sanger sequence data have been published. Here, more than 20 years after the last comprehensive classification of the family, we present the first familyâwide phylogenomic study of Cyperaceae based on targeted sequencing using the Angiosperms353 probe kit sampling 311 accessions. Additionally, 62 accessions available from GenBank were mined for overlapping reads and included in the phylogenomic analyses. Informed by this backbone phylogeny, a new classification for the family at the tribal, subtribal and generic levels is proposed. The majority of previously recognized suprageneric groups are supported, and for the first time we establish support for tribe Cryptangieae as a clade including the genus Koyamaea. We provide a taxonomic treatment including identification keys and diagnoses for the 2 subfamilies, 24 tribes and 10 subtribes and basic information on the 95 genera. The classification includes five new subtribes in tribe Schoeneae: Anthelepidinae, Caustiinae, Gymnoschoeninae, Lepidospermatinae and Oreobolinae. This article is protected by copyright. All rights reserved
The future of botanical monography : report from an international workshop, 12â16 March 2012, Smolenice, Slovak Republic
Monographs are fundamental for progress in systematic botany. They are the vehicles for circumscribing and naming
taxa, determining distributions and ecology, assessing relationships for formal classification, and interpreting long-term and
short-term dimensions of the evolutionary process. Despite their importance, fewer monographs are now being prepared by the
newer generation of systematic botanists, who are understandably involved principally with DNA data and analysis, especially
for answering phylogenetic, biogeographic, and population genetic questions. As monographs provide hypotheses regarding
species boundaries and plant relationships, new insights in many plant groups are urgently needed. Increasing pressures on
biodiversity, especially in tropical and developing regions of the world, emphasize this point. The results from a workshop (with
21 participants) reaffirm the central role that monographs play in systematic botany. But, rather than advocating abbreviated
models for monographic products, we recommend a full presentation of relevant information. Electronic publication offers
numerous means of illustration of taxa, habitats, characters, and statistical and phylogenetic analyses, which previously would
have been prohibitively costly. Open Access and semantically enhanced linked electronic publications provide instant access
to content from anywhere in the world, and at the same time link this content to all underlying data and digital resources used
in the work. Resources in support of monography, especially databases and widely and easily accessible digital literature
and specimens, are now more powerful than ever before, but interfacing and interoperability of databases are much needed.
Priorities for new resources to be developed include an index of type collections and an online global chromosome database.
Funding for sabbaticals for monographers to work uninterrupted on major projects is strongly encouraged. We recommend
that doctoral students be assigned smaller genera, or natural portions of larger ones (subgenera, sections, etc.), to gain the necessary expertise for producing a monograph, including training in a broad array of data collection (e.g., morphology, anatomy,
palynology, cytogenetics, DNA techniques, ecology, biogeography), data analysis (e.g., statistics, phylogenetics, models), and
nomenclature. Training programs, supported by institutes, associations, and agencies, provide means for passing on procedures
and perspectives of challenging botanical monography to the next generation of young systematists.Appreciation is expressed to: the Andrew W. Mellon Foundation
for financial support that allowed the workshop to be convened; the
International Association for Plant Taxonomy (IAPT) for additional
financial support for the workshop.http://www.botanik.univie.ac.at/iapt/s_taxon.phpam201
The future of botanical monography : report from an international workshop, 12â16 March 2012, Smolenice, Slovak Republic
Monographs are fundamental for progress in systematic botany. They are the vehicles for circumscribing and naming
taxa, determining distributions and ecology, assessing relationships for formal classification, and interpreting long-term and
short-term dimensions of the evolutionary process. Despite their importance, fewer monographs are now being prepared by the
newer generation of systematic botanists, who are understandably involved principally with DNA data and analysis, especially
for answering phylogenetic, biogeographic, and population genetic questions. As monographs provide hypotheses regarding
species boundaries and plant relationships, new insights in many plant groups are urgently needed. Increasing pressures on
biodiversity, especially in tropical and developing regions of the world, emphasize this point. The results from a workshop (with
21 participants) reaffirm the central role that monographs play in systematic botany. But, rather than advocating abbreviated
models for monographic products, we recommend a full presentation of relevant information. Electronic publication offers
numerous means of illustration of taxa, habitats, characters, and statistical and phylogenetic analyses, which previously would
have been prohibitively costly. Open Access and semantically enhanced linked electronic publications provide instant access
to content from anywhere in the world, and at the same time link this content to all underlying data and digital resources used
in the work. Resources in support of monography, especially databases and widely and easily accessible digital literature
and specimens, are now more powerful than ever before, but interfacing and interoperability of databases are much needed.
Priorities for new resources to be developed include an index of type collections and an online global chromosome database.
Funding for sabbaticals for monographers to work uninterrupted on major projects is strongly encouraged. We recommend
that doctoral students be assigned smaller genera, or natural portions of larger ones (subgenera, sections, etc.), to gain the necessary expertise for producing a monograph, including training in a broad array of data collection (e.g., morphology, anatomy,
palynology, cytogenetics, DNA techniques, ecology, biogeography), data analysis (e.g., statistics, phylogenetics, models), and
nomenclature. Training programs, supported by institutes, associations, and agencies, provide means for passing on procedures
and perspectives of challenging botanical monography to the next generation of young systematists.Appreciation is expressed to: the Andrew W. Mellon Foundation
for financial support that allowed the workshop to be convened; the
International Association for Plant Taxonomy (IAPT) for additional
financial support for the workshop.http://www.botanik.univie.ac.at/iapt/s_taxon.phpam201
Comparing recent PTA results on the nanohertz stochastic gravitational wave background
The Australian, Chinese, European, Indian, and North American pulsar timing
array (PTA) collaborations recently reported, at varying levels, evidence for
the presence of a nanohertz gravitational wave background (GWB). Given that
each PTA made different choices in modeling their data, we perform a comparison
of the GWB and individual pulsar noise parameters across the results reported
from the PTAs that constitute the International Pulsar Timing Array (IPTA). We
show that despite making different modeling choices, there is no significant
difference in the GWB parameters that are measured by the different PTAs,
agreeing within . The pulsar noise parameters are also consistent
between different PTAs for the majority of the pulsars included in these
analyses. We bridge the differences in modeling choices by adopting a
standardized noise model for all pulsars and PTAs, finding that under this
model there is a reduction in the tension in the pulsar noise parameters. As
part of this reanalysis, we "extended" each PTA's data set by adding extra
pulsars that were not timed by that PTA. Under these extensions, we find better
constraints on the GWB amplitude and a higher signal-to-noise ratio for the
Hellings and Downs correlations. These extensions serve as a prelude to the
benefits offered by a full combination of data across all pulsars in the IPTA,
i.e., the IPTA's Data Release 3, which will involve not just adding in
additional pulsars, but also including data from all three PTAs where any given
pulsar is timed by more than as single PTA.Comment: 21 pages, 9 figures, submitted to Ap
Comparing Recent Pulsar Timing Array Results on the Nanohertz Stochastic Gravitational-wave Background
The Australian, Chinese, European, Indian, and North American pulsar timing array (PTA) collaborations recently reported, at varying levels, evidence for the presence of a nanohertz gravitational-wave background (GWB). Given that each PTA made different choices in modeling their data, we perform a comparison of the GWB and individual pulsar noise parameters across the results reported from the PTAs that constitute the International Pulsar Timing Array (IPTA). We show that despite making different modeling choices, there is no significant difference in the GWB parameters that are measured by the different PTAs, agreeing within 1Ï. The pulsar noise parameters are also consistent between different PTAs for the majority of the pulsars included in these analyses. We bridge the differences in modeling choices by adopting a standardized noise model for all pulsars and PTAs, finding that under this model there is a reduction in the tension in the pulsar noise parameters. As part of this reanalysis, we "extended" each PTA's data set by adding extra pulsars that were not timed by that PTA. Under these extensions, we find better constraints on the GWB amplitude and a higher signal-to-noise ratio for the HellingsâDowns correlations. These extensions serve as a prelude to the benefits offered by a full combination of data across all pulsars in the IPTA, i.e., the IPTA's Data Release 3, which will involve not just adding in additional pulsars but also including data from all three PTAs where any given pulsar is timed by more than a single PTA
Model-based cross-correlation search for gravitational waves from the low-mass X-ray binary Scorpius X-1 in LIGO O3 data
Open data from the third observing run of LIGO, Virgo, KAGRA and GEO
The global network of gravitational-wave observatories now includes five
detectors, namely LIGO Hanford, LIGO Livingston, Virgo, KAGRA, and GEO 600.
These detectors collected data during their third observing run, O3, composed
of three phases: O3a starting in April of 2019 and lasting six months, O3b
starting in November of 2019 and lasting five months, and O3GK starting in
April of 2020 and lasting 2 weeks. In this paper we describe these data and
various other science products that can be freely accessed through the
Gravitational Wave Open Science Center at https://gwosc.org. The main dataset,
consisting of the gravitational-wave strain time series that contains the
astrophysical signals, is released together with supporting data useful for
their analysis and documentation, tutorials, as well as analysis software
packages.Comment: 27 pages, 3 figure
Search for Eccentric Black Hole Coalescences during the Third Observing Run of LIGO and Virgo
Despite the growing number of confident binary black hole coalescences
observed through gravitational waves so far, the astrophysical origin of these
binaries remains uncertain. Orbital eccentricity is one of the clearest tracers
of binary formation channels. Identifying binary eccentricity, however, remains
challenging due to the limited availability of gravitational waveforms that
include effects of eccentricity. Here, we present observational results for a
waveform-independent search sensitive to eccentric black hole coalescences,
covering the third observing run (O3) of the LIGO and Virgo detectors. We
identified no new high-significance candidates beyond those that were already
identified with searches focusing on quasi-circular binaries. We determine the
sensitivity of our search to high-mass (total mass ) binaries
covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to
compare model predictions to search results. Assuming all detections are indeed
quasi-circular, for our fiducial population model, we place an upper limit for
the merger rate density of high-mass binaries with eccentricities at Gpc yr at 90\% confidence level.Comment: 24 pages, 5 figure
Search for subsolar-mass black hole binaries in the second part of Advanced LIGOâs and Advanced Virgoâs third observing run
We describe a search for gravitational waves from compact binaries with at least one component with mass 0.2âMââ1.0âMâ and mass ratio q â„ 0.1 in Advanced LIGO and Advanced Virgo data collected between 1 November 2019, 15:00 UTC and 27 March 2020, 17:00 UTC. No signals were detected. The most significant candidate has a false alarm rate of 0.2yrâ1
â . We estimate the sensitivity of our search over the entirety of Advanced LIGOâs and Advanced Virgoâs third observing run, and present the most stringent limits to date on the merger rate of binary black holes with at least one subsolar-mass component. We use the upper limits to constrain two fiducial scenarios that could produce subsolar-mass black holes: primordial black holes (PBH) and a model of dissipative dark matter. The PBH model uses recent prescriptions for the merger rate of PBH binaries that include a rate suppression factor to effectively account for PBH early binary disruptions. If the PBHs are monochromatically distributed, we can exclude a dark matter fraction in PBHs fPBH âłâ0.6 (at 90% confidence) in the probed subsolar-mass range. However, if we allow for broad PBH mass distributions we are unable to rule out fPBH = 1. For the dissipative model, where the dark matter has chemistry that allows a small fraction to cool and collapse into black holes, we find an upper bound fDBH < 10â5 on the fraction of atomic dark matter collapsed into black holes
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