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Genomic analyses in Drosophila do not support the classic allopatric model of speciation
Get PDFFunding: European Research Council (Grant Number: ModelGenomLand 757648); Natural Environment Research Council (Grant Numbers: NE/L011522/1, NE/V001566/1).The allopatric model of speciation has dominated our understanding of speciation biology and biogeography since the Modern Synthesis. It is uncontroversial because reproductive isolation may readily emerge as a by-product of evolutionary divergence during allopatry unopposed by gene flow. Recent genomic studies have found that gene flow between species is common, but whether allopatric speciation is common has rarely been systematically tested across a continuum of closely related species. Here, we fit a range of demographic models of evolutionary divergence to whole-genome sequence data from 93 pairs of Drosophila species to infer speciation histories and levels of post-divergence gene flow. We find that speciation with gene flow is common, even between currently allopatric pairs of species. Estimates of historical gene flow are not predicted by current range overlap. Whilst evidence for secondary contact is generally limited, a few sympatric pairs showed strong support for a secondary contact model. Our analyses suggest that most speciation processes involve some long-term gene flow, perhaps due to repeated cycles of allopatry and contact, without requiring an extensive allopatric phase.Peer reviewe
Decolonising and depatriarchalising research cultures : a conversation with RAMA, the transnational Latin American women’s audiovisual research network
Get PDFConference panels allow for free-flowing conversation with panellists and the audience. They lead to insights that come through thinking together with people that can bring complementary knowledge to the discussion. Yet these exchanges can also be ephemeral with ideas evaporating as we engage with the next paper or panel discussion. We address this in a search for a lasting contribution to debates in this write up of a panel on women and cinema, for the conference ‘Women and Cinema in Ibero-America: Politics, Histories, Representations, Intersectionality’, at the Universidad Carlos III de Madrid in September 2022. We agreed that the topics and the discussion at our panel were of broad interest and provide food for thought for academics wanting to adopt a decolonial feminist approach. Topics that we discussed included, how to approach archival research in women’s film and video, and how to ‘depatriarchalise’ the archives, and democratise access to them, as fundamental to offering a feminist perspective in archival research; how to challenge a Western androcentric paradigm and auteurist perspectives that too often erase women’s contribution to film cultures; and, how to challenge epistemological barriers that deny women creators voices. In addition, the panel presented a first-hand perspective of eurocentrism and the experience of European academia for a researcher from Brazil and discuss how a decolonial feminist film curator/programmer can be a gate-opener rather than a gate-keeper.Peer reviewe
An active matter model captures spatial dynamics of actomyosin oscillations in larval epithelial cells during Drosophila morphogenesis
No full textFunding: E.D.M. acknowledges funding by the endowed E.N.&M.N. Lindsay PhD studentship. A.B. acknowledges funding by a St Leonard’s College World Leading Scholarship to M.B.&J.K. R.S. acknowledges support from the UK Engineering and Physical Sciences Research Council (Award EP/W023946/1).The apicomedial actomyosin network is crucial for generating mechanical forces in cells. Oscillatory behavior of this contractile network is commonly observed before or during significant morphogenetic events. For instance, during the development of the Drosophila adult abdominal epidermis, larval epithelial cells (LECs) undergo pulsed contractions before being replaced by histoblasts. These contractions involve the formation of contracted regions of concentrated actin and myosin. The emergence and control of pulsed contractions are not fully understood. Here, we combined in vivo 4D microscopy with numerical simulations of an active elastomer model applied to realistic cell geometries and boundary conditions informed by cell polarity to study in vivo subcellular spatial patterns of LEC actomyosin dynamics. The active elastomer model quantitatively reproduced in vivo observations. When compared to rectangular domains, simulations on realistic cell geometries showed systematically better agreement with experiments. We found that cell shape, cell polarity, and organization of the cell’s actomyosin network codetermine spatiotemporal network dynamics both in vivo and in simulations. Furthermore, the model predicted changes to LEC contractile activity under genetic perturbation of the actomyosin network. Our results show that cell geometry, accompanied by boundary conditions which reflect the cells’ polarity, is important to understanding the dynamics of the apicomedial actomyosin network. Moreover, our findings support the notion that spatiotemporal oscillatory behavior of the actomyosin network is an emergent property of the actomyosin network, rather than driven by upstream signaling.Peer reviewe
Complex families in the United Kingdom : mapping children’s diverse family pathways and their correlates from birth to age ten
Get PDFFunding: This research was funded by the Economic and Social Research Council (ESRC; grant number 2460061) facilitated by the Scottish Graduate School of Social Science (SGSSS). Júlia Mikolai’s work was funded by UK Research and Innovation (UKRI) under the UK government’s Horizon Europe funding Guarantee [grant number: EP/Y036441/1].The rise in divorce, cohabitation, non-marital childbearing and multi-partner fertility means that today’s children are more likely to experience less common or less stable family settings compared to previous generations. This may lead to increasing inequalities across the life course. Unlike most existing studies on family change, we investigate family trajectories in the United Kingdom from children’s perspective. We map the family trajectories characterising children’s first ten years of life using multi-channel sequence analysis on data from the UK Household Longitudinal Study, jointly capturing the dynamics of maternal partnership histories and paternal co-residence patterns from the children’s perspective. Multinomial logistic regression is applied to understand the characteristics associated with experiencing different childhood family trajectories. Children experience six typical family trajectories: continuously married; early separation; continuously cohabiting; later separation; early solo motherhood; and a new father. From birth to age ten, over a quarter of children do not continuously live with their two biological parents. Children with lower-educated mothers, mothers in the youngest or oldest groups, who live in urban areas, and belong to certain ethnic groups (White British, Mixed, Caribbean, Black African) tend to experience less common or less stable trajectories. Our elucidation of factors associated with more/less stable childhood family pathways can inform policy decision-making around support for families to mitigate growing short- and long-term inequalities giving rise to children’s diverging destinies.Peer reviewe
Unconventional magnetism and residual entropy in La7Os3O18
Get PDFFunding: The authors acknowledge funding from the Engineering and Physical Sciences Research Council via EP/P024564/1 (AWR), EP/T011130/1 (ASG) as well as the University of St Andrews for a St Leonard's College World-Leading Doctoral Scholarship (ATB), the International Max Planck Research School for Chemistry and Physics of Quantum Materials (MTP), and the EPSRC for characterisation infrastructure via EP/V034138/1, EP/L017008/1, EP/R023751/1, EP/T019298/1 and EP/T031441/1.In this communication we describe the crystal structure and unusual magnetic properties of La7Os3O18, a new layered osmate with structurally discrete (non-corner-sharing) octahedra containing Os5+ with S = 3/2 and strong spin–orbit coupling. Investigations through powder X-ray diffraction, magnetometry and heat capacity measurements demonstrate that the material undergoes an antiferromagnetic ordering transition at TN = 43 ± 1 K, with a further broad overturn in susceptibility at T ≈ 14 K indicating low dimensional short range magnetic ordering. Curie–Weiss fits give an effective moment of µeff = 3.26µB per Os5+ and Weiss constant of θW ≈ −92 K. Heat capacity data reveal that it is the low temperature feature with which the majority of the magnetic entropy is associated. However, between our lowest temperature of 2 K and well above TN we find only approximately half of the expected magnetic entropy to be released. Magnetisation versus field measurements at low temperature reveal a hysteretic metamagnetic transition above 5 T, further indicating that the magnetism below TN is non-trivial in nature.Peer reviewe
Catalytic approaches towards heterocyclic aziridine and aryl ethylamine scaffolds
Get PDFNitrogen-containing heterocyclic scaffolds are prevalent within bioactive molecules and natural products. Of these, aziridine scaffolds represent viable targets, both as bioactive molecules (e.g., as covalent inhibitors) but also as synthetic intermediates within the synthesis of amine-containing molecules. The research described within this thesis details the development of methodologies for the synthesis of heterocyclic aziridine and ethylamine scaffolds.
Despite notable advances, the preparation of complex, α-heterocyclic aziridine variants is particularly challenging, with few examples within the literature. This space is instead dominated by aliphatic and aromatic substituents, presenting a significant gap within the chemical literature. This chapter details the discovery and development of a general method to the diastereoselective synthesis of disubstituted heterocyclic aziridines. Brønsted acid‑catalysis provides access to an intermediate 1,2‑chloroamine, via aza-Michael addition to trisubstituted alkenes. Diastereocontrol of this addition was found to be reliant on trace amounts of acid, and simple SNi allowed access to a variety of cis‑aziridines with complete stereochemical fidelity (up to 20:1 d.r.), which are notoriously inaccessible through alternative synthetic methodologies.
Aryl triazole moieties have also demonstrated widespread applicability within materials science, medicinal chemistry and chemical biology. This chapter details the development of a one-pot, modular reaction which can access 1,4-disubstituted 1,2,3-triazolyl aryl ethylamine scaffolds from styrenes. The methodology employs a single copper catalyst, accessing an aryl aziridine in-situ using metal-nitrene aziridination, which is regioselectively ring-opened by sodium azide, with Cu acting as a Lewis acid. Finally, copper catalysed azide-alkyne cycloaddition (CuAAC) delivers the desired products with high yield. The scope of this transformation was explored, and the method was applied to a variety of pharmaceutically relevant motifs
Spectroscopy of free-floating planetary-mass objects and their disks with JWST
No full textFunding: B.D. and A.S. acknowledge support from the UKRI Science and Technology Facilities Council through grant ST/Y001419/1/. R.J. and L.F. acknowledge support for the JWST-GO-04583.008 program provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–03127. V.A.-A. acknowledges support from the INAF grant 1.05.12.05.03. K.M. acknowledges support from the Fundação para a Ciância e a Tecnologia (FCT) through the grant 2022.03809.CEECIND, and the Scientific Visitor Programme of the European Southern Observatory (ESO) in Chile. P.P. acknowledges funding from the UK Research and Innovation (UKRI) under the UK government’s Horizon Europe funding guarantee from ERC (under grant agreement No 101076489).Free-floating planetary-mass objects (FFPMOs) are known to harbor disks at young ages. Here, we present 1–13 μm spectra for eight young FFPMOs with masses of 5–10 MJup (at ages of 1–5 Myr), using the NIRSpec and MIRI instruments on the James Webb Space Telescope. We derive fundamental properties of these targets, and find spectral types of M9.5 to L4, with effective temperatures of 1600–1900 K. The photospheric spectra of our targets show a clear diversity at similar temperatures, especially in the 3–5 μm range, unaccounted for by existing atmospheric models. We find a silicate absorption feature in the photosphere of one of our targets, the first such detection in very young FFPMOs, indicating silicate clouds in their cool atmospheres. Six of our objects show mid-infrared excess emission above the photosphere, as well as silicate emission features, demonstrating the presence of disks. The shape and strength of the latter features constitute strong evidence of grain growth and crystallization, similar to what is seen in more massive brown dwarfs and stars. We also detect emission lines from hydrocarbon molecules in the disks of several targets. These are the lowest-mass isolated objects found so far with silicate and hydrocarbon emission features arising in their disks. The presence of disks and their characteristics point to the potential for the formation of rocky companions around free-floating planetary-mass objects.Peer reviewe
Tropical temperature distributions over a wide range of climates : theory and idealized simulations
No full textFunding: J. A. M. D. is supported by a St Leonard’s College Doctoral Scholarship awarded by the University of St Andrews, and M. P. B. is supported by the UKRI Frontier Research Guarantee scheme (Grant EP/Y027868/1).Understanding future changes in temperature variability and extremes is an important scientific challenge with societal impacts. Here, the responses of daily near-surface temperature distributions to climate warming are explored using an idealized GCM. Simulations of a wide range of climate states are performed using both a slab-ocean aquaplanet configuration and a simple continental configuration with a bucket-style model for land hydrology. In the tropics, the responses of extreme temperatures to climate change contrast strongly over land and ocean. Over land, warming is amplified for hot days relative to the average summer day. But over ocean, warming is suppressed for hot days, implying a narrowing of the temperature distribution. Previous studies have developed theories based on convective coupling to interpret changes in extreme temperatures over land. Building on that work, the contrasting temperature distribution responses over land and ocean are investigated using a novel theoretical framework based on local convective coupling. The theory highlights five physical mechanisms with the potential to drive differential warming across temperature percentiles: free-tropospheric temperature change, relative humidity change, convective available potential energy (CAPE) change, the hot-get-hotter mechanism, and the drier-get-hotter mechanism. Hot days are relatively dry over land due to limited moisture availability, which drives the drier-get-hotter mechanism and amplified warming of the warm tail of the distribution. This mechanism is the primary factor explaining the contrasting responses of hot days over land and ocean to climate change, but other mechanisms also contribute to changing the temperature distribution, with changes in free-tropospheric temperature and surface relative humidity having large influences (which partially cancel).Peer reviewe
Resonant interlayer coupling in NbSe2-graphite epitaxial moiré superlattices
No full textFunding: The authors gratefully acknowledge support from the UK Engineering and Physical Sciences Research Council (Grants Nos. EP/X015556/1 and EP/M023958/1). M.S.B. acknowledges support from Leverhulme Trust (Grant No. RPG-2023-253). K. K. was supported by the CDT in Graphene NOWNANO. A.A. had support from the Indonesia Endowment Fund for Education (LPDP), NIB/202209223311735. R.V.B. and M.S.B. are grateful to E-IMR center at the Institute for Materials Research, Tohoku University, for continuous support.Moiré heterostructures, created by stacking 2D materials together with a finite lattice mismatch or rotational twist, represent a new frontier of designer quantum materials. Typically, however, this requires the painstaking manual assembly of heterostructures formed from exfoliated materials. Here, clear spectroscopic signatures of moiré lattice formation in epitaxial heterostructures of monolayer (ML) NbSe2 grown on graphite substrates are observed. Angle-resolved photoemission measurements and theoretical calculations of the resulting electronic structure reveal moiré replicas of the graphite π states forming pairs of interlocking Dirac cones. Interestingly, these intersect the NbSe2 Fermi surface at the k-space locations where NbSe2's charge-density wave (CDW) gap is maximal in the bulk. This provides a natural route to understand the lack of CDW enhancement for ML-NbSe2/graphene as compared to a more than fourfold enhancement for NbSe2 on insulating support substrates, and opens new prospects for using moiré engineering for controlling the collective states of 2D materials.Peer reviewe
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