Latitudinal Movement Research Articles

Investigating historical drivers of latitudinal gradients in polyploid plant biogeography: A multiclade perspective.

The proportion of polyploid plants in a community increases with latitude, and different hypotheses have been proposed about which factors drive this pattern. Here, we aimed to understand the historical causes of the latitudinal polyploidy gradient using a combination of ancestral state reconstruction methods. Specifically, we assessed whether (1) polyploidization enables movement to higher latitudes (i.e., polyploidization precedes occurrences in higher latitudes) or (2) higher latitudes facilitate polyploidization (i.e., occurrence in higher latitudes precedes polyploidization). We reconstructed the ploidy states and ancestral niches of 1032 angiosperm species at four paleoclimatic time slices ranging from 3.3 million years ago to the present, comprising taxa from four well-represented clades: Onagraceae, Primulaceae, Solanum (Solanaceae), and Pooideae (Poaceae). We used ancestral niche reconstruction models alongside a customized discrete character evolution model to allow reconstruction of states at specific time slices. Patterns of latitudinal movement were reconstructed and compared in relation to inferred ploidy shifts. No single hypothesis applied equally well across all analyzed clades. While significant differences in median latitudinal occurrence were detected in the largest clade, Poaceae, no significant differences were detected in latitudinal movement in any clade. Our preliminary study is the first to attempt to connect ploidy changes to continuous latitudinal movement, but we cannot favor one hypothesis over another. Given that patterns seem to be clade-specific, more clades must be analyzed in future studies for generalities to be drawn.

Spatiotemporal Characteristics and Rainfall Thresholds of Geological Landslide Disasters in ASEAN Countries

Spatiotemporal Characteristics and Rainfall Thresholds of Geological Landslide Disasters in ASEAN Countries

Statistical reanalysis of Archean zircon paleointensities: No evidence for stagnant-lid tectonics

The initiation of mobile-lid plate tectonics on Earth represented a critical transition towards a more familiar world in terms of surface temperature stabilization, biogeochemical cycling, topography creation, and other processes. Zircon-based estimates of the geomagnetic field intensity have recently been cited as providing evidence for the lack of mobile-lid motion between 3.9 and 3.4 billion years ago (Ga). We reanalyze the published dataset of 91 zircon paleointensities from the Jack Hills (Australia) and Green Sandstone Bed (GSB; South Africa) localities within this time interval and, using both analytical and bootstrap resampling approaches, show that the small number of samples result in large uncertainties in implied paleolatitude. Specifically, in more likely scenarios that do not assume coherent motion for both localities, all latitudinal displacements on Earth are permitted within the 95 % confidence interval. We also examine the less likely scenario that the two landmasses shared a motion history, which increases the data density and presents the best-case scenario for constraining latitudinal motion. In this case, the 95 % confidence interval of the zircon paleointensity data is compatible with the displacements of between 35 % and 52 % of modern continental localities, all of which experience mobile-lid tectonics. Finally, generating expected paleointensity time series for modern continents undergoing mobile-lid motion shows that about two-thirds of these motions would not be resolved by zircon paleointensities, even in the best-case scenario of combining Jack Hills and GSB datasets. All of these analyses assume that these zircons retain a primary paleomagnetic signal, an assertion which is opposed by a number of published zircon magnetism studies. We conclude that Archean zircon paleointensities do not provide evidence for or against mobile-lid plate tectonics prior to 3.4 Ga. Future paleomagnetic investigation of tectonic regime on the early Earth should therefore focus on magnetization directions in well-preserved, oriented whole rocks.

Analysis of the Geodesic Motions of Massive Particles in Kerr–Sen–AdS4 Spacetime

We consider geodesic motions in Kerr–Sen–AdS4 spacetime. We obtain equations of motion for light rays and test particles. Using parametric diagrams, we show some regions where radial and latitudinal geodesic motions are allowed. We analyze the impact of parameters related to the dilatonic scalar on the orbit and find that it will result in more rich and complex orbital types.

Synchronous anti-phase variations between the East Asian summer monsoon and South America Summer Monsoon during Heinrich stadial 2

The interhemispheric anti-phase variation of monsoonal precipitation at the millennial timescale has been attributed to the latitudinal movement of the Intertropical Convergence Zone (ITCZ). However, a debate persists regarding the lead-lag or synchronous relationship between the Asian Summer Monsoon (ASM) and South American Summer Monsoon (SASM) on the onset and termination timings of the Heinrich stadials, hindering a deeper understanding of their underlying driving mechanisms. Here, we presented a new stalagmite δ18O record from Xianyun Cave, southeastern China. This record, with ∼5-year temporal resolution and an averaged uncertainty of ∼60 years on U–Th dates, spans Heinrich Stadial 2 (HS2) and represents East Asian Summer Monsoon (EASM) intensity variations. Based on our record, we further divided the evolution of the EASM during HS2 into three phases: an onset phase (HS2-I, 24,450–24,260 yr BP) and a termination phase (HS2-III, 23,950–23,630 yr BP), sandwiching a phase with relatively intensified monsoon (HS2-II, 24,260–23,950 yr BP). During the onset and termination of HS2, synchronous transition in monsoon records from both hemispheres was observed, driven by the large-scale meridional movement of the ITCZ. In HS2-I, a “Large excursion” observed in both tropical ISM and SASM records was also evidenced in the Xianyun record, suggesting an extension of the “Tropical atmospheric seesaw” to broader regions near tropical moisture sources. In phase II, our record precisely characterizes a centennial-scale strengthening of the EASM coinciding with a weakening SASM, while the Indian Summer Monsoon (ISM) showed no significant changes. The decoupling of the ISM and EASM may be related to the distinct responses of the regional ITCZ to El Niño-Southern Oscillation variabilities. Our study highlights the significant role of the tropical ocean-atmosphere coupling systems in the synchronized or divergent evolution of global monsoons within Heinrich stadials.

Climate-related habitat variations of Humboldt squid in the eastern equatorial Pacific Ocean

An integrated habitat suitability index (HSI) model was developed in this study for Dosidicus gigas in the eastern equatorial waters of the Pacific Ocean to explore climate-related spatial and temporal variability in the habitat distribution pattern based on three crucial environmental variables: sea surface temperature (SST), sea surface salinity (SSS) and chlorophyll-a concentration (Chl-a). Results revealed that the HSI model could accurately predict potential habitats for D. gigas. The habitat suitability varied significantly by month, with highest suitability in April and lowest in March. Besides, from December to May, the longitudinal gravity center of the fishing grounds (LONG) and the HSI overall shifted eastward and the latitudinal gravity center shifted northward then southward. In comparison to the warm ENSO phases in 2019, the cold ENSO phases in 2018 produced increased suitable habitat from December to May, leading to a significantly higher CPUE. Prospective high-quality habitats in 2018 primarily occurred in the western regions, with the exception of December, which resulted in a more westward distribution of LONG from January to May. High-quality habitats moved northward from December to February and southward from March to May 2018, compared to minor latitudinal movement in 2019. It was inferred that annual variations in squid abundance and distribution were largely affected by the SST-related habitat pattern of D. gigas in the eastern equatorial waters. Our findings suggested that D. gigas habitats clearly varied by month and year and were greatly influenced by climate-induced environmental changes.

Geochemical records provide evidences for the evolution of the marine redox environment in the southwestern Sumatra waters over the past 35,000 years

The marine redox environment (MRE) can affect marine productivity and nutrient cycling, as well as governs material and energy transport. However, its evolution process and driving mechanism in different historical periods revealed significant regional characteristics. Southwestern Sumatra waters, located at the Indo-Pacific Ocean convergence, are an ideal region for studying the evolution of MRE due to significant upwelling and variable productivity levels resulting from the seasonal monsoonal activity. In this study, based on the sediment core SO184–10043, systematic trace element geochemical analysis was conducted for reconstructing the MRE over the past 35,000 years using redox proxies, namely, Ni/Co, U/Th, and biogenic Barium (Babio). Ni/Co and U/Th varied in a range of 1–4 and 0.2–1, indicating general oxic conditions with matching productivity levels indicated by Babio (ranging from 300 × 10–6 to 580 × 10–6). A comparison with other reconstructed archives indicated that the MRE records of the sediment core in this study were in consistence in responding to the high-latitude climate records with strong semi-precession and millennial fluctuations. Suggestively, these fluctuations correspond to the natural summertime insolation, triggering the latitudinal motions of the Intertropical Convergence Zone (ITCZ), as well as leading to corresponding changes in the seasonal Indian monsoon system. Freshwater lids modulate the mixing effect by acting as barriers and influencing the upwelling development, thereby leading to strong oxic conditions in the MRE. Therefore, robust evidence on the millennial-scale variability in MRE driven by the ITCZ movement and regional monsoon changes in the tropical Indian Ocean is provided by the trace element archives employed in the present study, thereby providing novel insights into the evolution of MRE in response to global and local climate changes.

3D motion model for the freefall lifeboat during its launching from a moving ship

Studying a lifeboat’s launch motion mechanism is essential for safe marine evacuation. Motion modeling and simulation offer an effective approach for analyzing the motion characteristics of lifeboat launches under different environmental conditions. However, existing models of the complete launch process for a freefall lifeboat (FFLB) do not capture the latitudinal motion of both the FFLB and its parent body, resulting in models with reduced accuracy and general applicability. To address this issue, we propose a 3D motion model for FFLB launch from a moving ship using Kane’s method. The launch process is divided into the sliding phase and the water entry phase. To account for the impact of ship motion on the lifeboat during the sliding phase, we utilize the mathematical model of Manoeuvring Modelling Group (MMG) to simulate the ship’s motion in waves. Contact forces between the FFLB and the skid are calculated using the node-to-segment method based on elasticity and friction theory. During the water entry phase, hydrodynamic forces are calculated using the strip method, and the slamming force is captured by employing the asymmetric water entry of a finite wedge. Flow separation from the lifeboat’s body is calculated by introducing a fictitious body surface. Our experiments verify the accuracy of the model, with acceleration curves matching well, and a 20% maximum relative error of acceleration extremes during the water entry phase. The simulation results indicate that ship latitudinal motion leads to a similar motion of the FFLB. The ship’s longitudinal motion affects the maximum acceleration of the FFLB and may cause it to setback after water entry. Additionally, the occupants experience less impact when the FFLB enters the water near the wave crest.

On the Connection between Rieger-type and Magneto-Rossby Waves Driving the Frequency of the Large Solar Eruptions during Solar Cycles 19–25

Global solar activity variation mainly occurs over about an 11 yr cycle. However, both longer and shorter periodicities than the solar cycle are also present in many different solar activity indices. The longer timescales may be up to hundreds of years, while the shorter timescales for global solar variability could be within 0.5–2 yr, which include, e.g., from the Rieger-type periods (150–160 days) to quasi-biennial oscillations of 2 yr. The most likely origin of this short-timescale quasi-periodicity is attributed to magnetic Rossby waves, which have periods of 0.8–2.4 yr. In this work, we present findings of a unique evolution of identified shorter periodicities, like the Rieger-type, arising from magnetic Rossby waves, throughout Solar Cycles 19–25. We report further observational evidence of the strong relationship between the Rieger-type periodicity, magneto-Rossby waves, and major solar flare activity. Moreover, this study also reveals that the global solar magnetic field has a continuous periodic longitudinal conveyor belt motion along the solar equator, together with an up-and-down movement in the latitudinal directions. We found that when these longitudinal and latitudinal movements have Rieger-type periodicity and magneto-Rossby waves during the same period of a solar cycle, major flare activity is present.

ПЕТРО-ПАЛЕОМАГНИТНАЯ ХАРАКТЕРИСТИКА ГАББРОДИОРИТОВ НИЖНЕАМУРСКОГО КОМПЛЕКСА ЖУРАВЛЕВСКО-АМУРСКОГО ТЕРРЕЙНА (СИХОТЭ-АЛИНЬСКИЙ ОРОГЕННЫЙ ПОЯС)

The paper presents the results of paleomagnetic and rock magnetic studies on phase-I gabbrodiorites of the Lower Amur Complex of the Zhuravlevka-Amur terrane (Poni massif, Poni-Mulinsky ore cluster), which were used to determine that at the time the Lower Amur intrusive Complex formation (Cenomanian-Turonian) the Priamurskaya zone was located between the Central Sikhote-Alin fault in the east and the Priamursky fault in the west, which is 10–13° north of its current position. It is shown that starting from the middle of the Cenomanian there were no latitudinal movements of the Priamurskaya zone of the Zhuravlevka-Amur terrane relative to the Eurasian continent. However, a more than 20-degree counterclockwise rotation of the zone relative to the continent was recorded, which is easily interpreted in terms of the ball-bearing model invoking an action of the Amur and Central Sikhote-Alin en echelon left-lateral strike-slip faults. Left-lateral strike-slip fault systems could easily be channels for mantle material supply during the formation of the largest porphyry copper deposit Malmyzh, which, along with the Poni-Mulinsky ore cluster, is part of the Lower Amur mineragenic zone.

The velocity of postglacial migration of fire-adapted boreal tree species in eastern North America

The Earth's climate has been warming rapidly since the beginning of the industrial era, forcing terrestrial organisms to adapt. Migration constitutes one of the most effective processes for surviving and thriving, although the speed at which tree species migrate as a function of climate change is unknown. One way to predict latitudinal movement of trees under the climate of the twenty-first century is to examine past migration since the Last Glacial Maximum. In this study, radiocarbon-dated macrofossils were used to calculate the velocity of past migration of jack pine (Pinus banksiana) and black spruce (Picea mariana), two important fire-adapted conifers of the North American boreal forest. Jack pine migrated at a mean rate of 19 km per century (km-cent) from unglaciated sites in the central and southeastern United States to the northern limit of the species in subarctic Canada. However, the velocity increased between unglaciated and early deglaciated sites in southern Quebec and slowed from early to mid-Holocene in central and eastern Quebec. Migration was at its lowest speed in late-Holocene times, when it stopped about 3,000 y ago. Compared with jack pine, black spruce migrated at a faster mean rate of 25 km-cent from the ice border at the last interstadial (Bølling/Allerød) to the species tree limit. The modern range of both species was nearly occupied about 6,000 y ago. The factors modulating the changing velocity of jack pine migration were closely associated with the warm-dry climate of the late Pleistocene-Holocene transition and the more humid climate of the mid- and late-Holocene.

Latitudinal variations in the nocturnal behaviour of OI 630 nm airglow emissions and their relationship with equatorial electrodynamics

Airglow emissions from the thermosphere act as tracers of the behaviour of the upper atmosphere. OI 630 nm nightglow emissions that originate from an altitude of around 250 km in the thermosphere have been investigated using a large field-of-view ground-based optical spectrograph from Mt. Abu (24.6°N, 72.7°E, 19°N Mag.), a low-latitudinal location in India. The latitudinal movement of the crest of the equatorial ionization anomaly (EIA) in both poleward in the evening and equatorward in the night has been reported using the OI 630 nm nightglow emissions. The EIA crest is found to shift away from the equator after the sunset, which has been shown to be directly related to the strength of the twilighttime equatorial electrodynamics. Later in the night, after 20 LT, a clear movement of the crest back towards the equator, known as the reversal of EIA, has been observed. The speeds of the EIA reversals for forty nights in the years 2014 and 2015 have been obtained and are found to be in the range of 10–55 ms−1. As the global equatorial electric fields (E) are irrotational in nature (∇×E=0), simultaneous variations in the daytime electrojet strength over Jicamarca in the American sector have been compared with the nighttime reversal speeds of the EIA over the Indian sector, which show a remarkable relationship with each other. Thus, it is hereby demonstrated that the reversal in EIA as inferred by the OI 630 nm nightglow emissions in our measurements is due to the westward equatorial electric field. It is hereby proposed that the reversal speed derived from optical nightglow measurements can serve as a proxy for the determination of westward electric field over equator for that longitude sector.

Weighing the Galactic disk using phase-space spirals

We have applied our method to weigh the Galactic disk using phase-space spirals to the proper motion sample of Gaia’s early third release (EDR3). For stars in distant regions of the Galactic disk, the latitudinal proper motion has a close projection with vertical velocity, such that the phase-space spiral in the plane of vertical position and vertical velocity can be observed without requiring that all stars have available radial velocity information. We divided the Galactic plane into 360 separate data samples, each corresponding to an area cell in the Galactic plane in the distance range of 1.4–3.4 kpc, with an approximate cell length of 200–400 pc. Roughly half of our data samples were disqualified altogether due to severe selection effects, especially in the direction of the Galactic centre. In the remainder, we were able to infer the vertical gravitational potential by fitting an analytic model of the phase-space spiral to the data. This work is the first of its kind, in the sense that we are weighing distant regions of the Galactic disk with a high spatial resolution, without relying on the strong assumptions of axisymmetry. Post-inference, we fitted a thin disk scale length of 2.2 ± 0.1 kpc, although this value is sensitive to the considered spatial region. We see surface density variations as a function of azimuth of the order of 10–20%, which is roughly the size of our estimated sum of potential systematic biases. With this work, we have demonstrated that our method can be used to weigh distant regions of the Galactic disk despite strong selection effects. We expect to reach even greater distances and improve our accuracy with future Gaia data releases and further improvements to our method.

Heating or Cooling: Study of Advective Heat Transport in the Inflow and the Outflow of Optically Thin Advection-dominated Accretion Flows

Advection is believed to be the dominant cooling mechanism in optically thin advection-dominated accretion flows (ADAFs). When outflow is considered, however, the first impression is that advection should be of opposite sign in the inflow and the outflow, due to the opposite direction of radial motion. Then how is the energy balance achieved simultaneously? We investigate the problem in this paper, analyzing the profiles of different components of advection with self-similar solutions of ADAFs in spherical coordinates (r θ ϕ). We find that for n < 3γ/2 − 1, where n is the density index in ρ ∝ r −n and γ is the heat capacity ratio, the radial advection is a heating mechanism in the inflow and a cooling mechanism in the outflow. It becomes 0 for n = 3γ/2 − 1, and turns to a cooling mechanism in the inflow and a heating mechanism in the outflow for n > 3γ/2 − 1. The energy conservation is only achieved when the latitudinal (θ direction) advection is considered, which takes an appropriate value to maintain energy balance, so that the overall effect of advection, no matter the parameter choices, is always a cooling mechanism that cancels out the viscous heating everywhere. For the extreme case of n = 3/2, latitudinal motion stops, viscous heating is balanced solely by radial advection, and no outflow is developed.

Synchronous millennial surface-stratified events with AMOC and tropical dynamic changes in the northeastern Indian Ocean over the past 42 ka

The ocean heat content (OHC) and associated surface stratification in tropical oceans are ideal variables to monitor global climate change. However, the variations in surface stratification of the tropical Indian Ocean at the millennial time scale have been less understood. In this context, the present study aimed at reconstructing the sea surface temperature (SST) and thermocline water temperature (TWT) using Mg/Ca of planktonic foraminifera in the sediments of the Andaman Sea, which is one of the hot centers in the Indo-Pacific warm pool (IPWP) over the past 42 ka. The study results confirm the SST changes are consistent in response to the high-latitude temperature records with strong sub-orbital and millennial variations, while the TWT patterns trend remarkably different from the millennial-scale SST and show the variations correspond to the natural summer insolation that triggers the latitudinal movements of the Intertropical Convergence Zone (ITCZ). Furthermore, salinity influences the thermal differences (ΔT=SST-TWT) by varying the vertical temperature and stratification. Analysis of available data shows that the mean northward position of ITCZ would input more freshwater into the Andaman Sea. Freshwater lids can reduce mixing by acting as effective barriers and preventing heat from transferring from the surface to the subsurface, thereby causing subsurface cooling and increased stratification. In contrast, more southward ITCZ (boreal winter monsoon) supplies less freshwater into the Andaman Sea. A highly saline surface water and air cooling promotes mixing and subsurface warming, resulting in decreased stratification. The study results reveal a millennial-scale vertical thermal seesaw synchronizing in the tropical Indian Ocean with abrupt Atlantic meridional overturning circulation (AMOC) changes. During the Bolling-Allerod (B/A) warming period, the dynamic AMOC maintains the surface water stratification by controlling the subsurface cooling processes with increased precipitation and freshwater brought by the northward ITCZ. In contrast, Younger Dryas (YD) and Heinrich events (H) are characterized by reduced summer monsoon precipitation associated with the sluggish AMOC and southward ITCZ, resulting in less stratification and subsurface warming in the Andaman Sea. The thermal proxy records adopted in the study afford robust evidence on the millennial-scale variability in surface stratification driven synchronously by AMOC and regional evaporation vs. precipitation changes in the tropical Indian Ocean, offering new insights into the impacts of the IPWP OHC on abrupt climate changes.

PALEOMAGNETISM OF QUATERNARY VOLCANISM OF THE MOUNT NEMRUT

As a result of the convergence between the Arabian plate and the Anatolian block, a continentcontinent collision occurred in the region along the Bitlis Zargos sutur zone. Following the collision, volcanic activity began in the Late Miocene and produced volcanic material throughout the region and reach to the Caucasus. Collision-related volcanism in eastern Anatolia covered almost two-thirds of the area and formed volcanic products up to 1 km thick. In order to determine the tectonic evolution of Mount Nemrut and its around, paleomagnetic core samples were collected from a total of 11 sites from Pleistocene - Holocene time interval aged volcanic rocks. Paleomagnetic laboratory studies were carried out in KANTEK Paleomagnetism Laboratory, and also rock magnetism studies were carried out in Istanbul University-Cerrahpaşa, Yılmaz İspir Paleomagnetism Laboratory. When the mean magnetization directions obtained from Mount Nemrut and its surrounding Holocene and Upper Pleistocene aged locations are examined, it is seen that there is an average of 7.3° clockwise rotation. It is also observed that the angle of inclination is 60°. These results obtained, considering the α95 circle (7.7°), it is observed that there is no tectonic rotation within the sensitivity limits of paleomagnetism in the region. At the same time, it can be interpreted that Mount Nemrut has not been exposed to a latitudinal movement since the Quaternary, but volcanics is still at the latitude where it was formed.

Developing lacustrine sedimentary records of storminess in southwestern New Zealand

Variability of the Southern Hemisphere westerly winds (SWW) are the dominant feature of the climatology of the Southern Hemisphere and they are reflected in the Southern Annular Mode (SAM) which is defined as the difference in the zonal mean sea level pressure at 40°S and 65°S and is expressed as a latitudinal movement in the westerly circulation system. Meteorological data suggests that the SAM plays an important role in modern weather and climate of the Southern Hemisphere. Palaeostudies show that the westerly circulation system established its northern limits of present day airflow by the mid Holocene but the records from South America remain out of phase with those from the SW Pacific. In this study we report on the development of a flood frequency hydrological proxy that is based on the recognition of rapidly deposited layers preserved in lake sediments in southern South Island, New Zealand. Four distinct climate states can be identified: low storm frequency between 10 and 8 cal ka BP; moderate storm frequency between 8 and 5.5 cal ka BP, high storm frequency between 5.5 and 4 cal ka BP and low storm frequency between 4 cal ka BP and 750 cal a BP. A post-750 cal a BP increase storm frequency is likely to be a result of Polynesian vegetation disturbance. These four distinct climate states are driven by variations in the strength or persistence of westerly airflow. Comparison with similar records from east coast of the North Island, New Zealand and Ecuador suggest that all three sites experienced an increase in storm frequency in the middle Holocene. Divergence in the records in the late Holocene can be attributed to variability in the strength of ENSO and SAM in different locations.

Deformation understanding in the Upper Paleozoic of Ventana Ranges at Southwest Gondwana Boundary

At the east of the Ventana Ranges, Buenos Aires, Argentina, outcrops the Carboniferous-Permian Pillahuincó Group (Sauce Grande, Piedra Azul, Bonete and Tunas Formation). We carried out an Anisotropy of Magnetic Susceptibility (AMS) study on Sauce Grande, Piedra Azul and Bonete Formation that displays ellipsoids with constant Kmax axes trending NW–SE, parallel to the fold axes. The Kmin axes are orientated in the NE–SW quadrants, oscillating from horizontal (base of the sequence-western) to vertical (top of the sequence-eastern) positions, showing a change from tectonic to almost sedimentary fabric. This is in concordance with the type and direction of foliation measured in petrographic thin sections which is continuous and penetrative to the base and spaced and less developed to the top. We integrated this study with previous Tunas Formation results (Permian). Similar changes in the AMS pattern (tectonic to sedimentary fabric), as well as other characteristics such as the paleo-environmental and sharp curvature in the apparent polar wander path of Gondwana, marks a new threshold in the evolution of the basin. Those changes along the Pillahuincó deposition indicate two different spasm in the tectonic deformation that according to the ages of the rocks are 300–290 Ma (Sauce Grande to Bonete Formation deposition) and 290–276 Ma (Tunas Formation deposition). This Carboniferous-Permian deformation is locally assigned to the San Rafael (Hercinian) orogenic phase, interpreted as the result of rearrangements of the microplates that collided previously with Gondwana, and latitudinal movements of Gondwana toward north and Laurentia toward south to reach the Triassic Pangea.

Epicyclic oscillations of test particles near marginally stable circular orbits around charged Kiselev black holes

The marginally stable circular orbits (MSCOs) of test particles in the spacetime exterior to a charged Kiselev black hole are investigated for three characteristic values of the equation of state parameter ${\ensuremath{\omega}}_{q}$, namely (i) ${\ensuremath{\omega}}_{q}=\ensuremath{-}1/3$, (ii) ${\ensuremath{\omega}}_{q}=\ensuremath{-}1$, and (iii) ${\ensuremath{\omega}}_{q}=\ensuremath{-}2/3$, and for different values of the normalization factor $\ensuremath{\alpha}$ and electric charge $Q$ of the black hole. It is found that the presence of the quintessence field shifts outward the innermost stable circular orbits (ISCOs) around the Kiselev black hole, having the same charge parameter $Q$, as compared to the ISCOs around a Riessner-Nordstrom black hole, while the effect of the quintessence field on the outermost stable circular orbits (OSCOs) is just opposite to that on the ISCOs. Further, the radii of the photon circular orbits are also calculated for different ranges of the parameters $\ensuremath{\alpha}$ and $Q$. It is observed that the photon orbits are also shifted outward as the value of $\ensuremath{\alpha}$ increases. The radial and latitudinal epicyclic motion of test particles, which can be related to the quasiperiodic oscillations of test particles slightly above the MSCOs in the vicinity of the charged Kiselev black hole, is analyzed for the three different values of ${\ensuremath{\omega}}_{q}$. It is seen that the azimuthal and latitudinal frequencies coincide, and the radial epicyclic frequency is different in dependence on the spacetime parameters. In the case of ${\ensuremath{\omega}}_{q}=\ensuremath{-}1/3$, the azimuthal and latitudinal frequencies depend on the radial position $r$ of the particle, the charge $Q$, and the mass $M$ of the black hole, and do not depend on the factor $\ensuremath{\alpha}$. However, for ${\ensuremath{\omega}}_{q}=\ensuremath{-}2/3$ and ${\ensuremath{\omega}}_{q}=\ensuremath{-}1$, these two frequencies, along with the black hole parameters---i.e., $M$ and $Q$ and the radial position $r$---also depend on the factor $\ensuremath{\alpha}$. The radial epicyclic frequency for all the values of ${\ensuremath{\omega}}_{q}$ depends on $M$, $Q$, $r$, and also on the normalization factor $\ensuremath{\alpha}$. We also compare the epicyclic frequencies with that for an uncharged black hole. With the increase of electric charge, the ISCO becomes closer to the central object, and one can observe epicyclic frequencies closer to the central object, which makes the epicyclic frequencies larger. The ISCO gets larger as $\ensuremath{\alpha}$ increases, and thus the epicyclic frequencies can be observed away from the central object and would be smaller as compared to the case of a pure Riessner-Nordstrom black hole without quintessence. As the effect of the parameters $Q$ and $\ensuremath{\alpha}$ on the OSCOs is just opposite to that on the ISCOs, the epicyclic frequencies near the OSCOs behave the other way around.

Ecological specialization promotes diversity and diversification in the Eastern Mediterranean genus Ricotia (Brassicaceae)

AbstractDespite its amazing biodiversity, the Eastern Mediterranean remains a highly understudied region when compared with the Western Mediterranean, restricting our understanding of diversity across the entire Mediterranean. Here we use a combination of molecular markers and presence/absence data from all species of the Eastern Mediterranean genus Ricotia collected across its full geographic range to determine historical, ecological, and evolutionary factors responsible for lineage‐specific diversification in the Eastern Mediterranean. Network analysis based on molecular data revealed a high genetic structure within all lineages, and phylogenetic reconstructions based on the multispecies coalescent showed that within‐lineage diversification corresponded to the onset of the Mediterranean climate. Reconstruction of ancestral histories indicates that the genus originated within Anatolia and spread across the Eastern Mediterranean and Levant using the Taurus mountains. Ecological niche models suggest that local populations did not go through any major distributional shifts and have persisted in present‐day habitats since the Last Glacial Maximum. Furthermore, niche differentiation tests revealed significant differences between closely related species and showed the main variables predicting species limits to be different for each species. Our results give crucial information on the patterns and processes shaping diversity in the Eastern Mediterranean and show the main factors promoting diversification to be local environmental dynamics and ecological specialization and not large‐scale latitudinal movements, as often reported for southern Europe. By determining local and regional patterns of diversification in an Eastern Mediterranean genus, we further our understanding of the major trends influencing plant diversity in the Mediterranean basin as a whole.