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Chkhikvadze, J. N.; Kakhiani, V. O.; Djaniashvili, E. B.

doi:10.1023/a:1015386323943

Cited by 3 publications

(3 citation statements)

References 2 publications

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“…de Lattin, 1967;Tuniyev, 1990Tuniyev, , 1995Myers et al, 2000), and it seems highly unlikely that stripe-necked terrapins invaded these regions only in the Holocene. Evidence for the long-lasting existence of terrapins is also provided by the fossil record (Chkhikvadze, 1983(Chkhikvadze, , 1989. The phylogenetically differentiated clade of haplotypes Cmt7-Cmt10, nearly entirely confined to Anatolia, suggests that a distinct refuge existed there.…”

Section: Phylogeographymentioning

confidence: 97%

“…This is in accord with the fossil record and mtDNA differentiation (see below). Mauremys are known from the Medial to Upper Miocene of the Transcaucasus (Chkhikvadze, 1983(Chkhikvadze, , 1989Danilov, 2005) and the United Arab Emirates (de Lapparent de Broin & van Dijk, 1999), while the oldest records for the Balkan Peninsula and Crete date only to the Pleistocene (Simonelli Cave, Crete: Kotsakis, 1977;Megalopolis, Peloponnese: Melentis, 1966;Bachmayer & Symeonidis, 1970), implying recent arrival of M. rivulata there. This could explain its weak mtDNA differentiation revealed in this study as well as in a previous investigation focusing on M. rivulata from Greece (Mantziou et al, 2004).…”

Section: Phylogeographymentioning

confidence: 99%

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Go east: phylogeographies of Mauremys caspica and M. rivulata– discordance of morphology, mitochondrial and nuclear genomic markers and rare hybridization

Fritz

Ayaz

Buschbom³

et al. 2008

J of Evolutionary Biology

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In recent years many cases of hybridization and introgression became known for chelonians, requiring a better understanding of their speciation mechanisms. Phylogeographic investigations offer basic data for this challenge. We use the sister species Mauremys caspica and M. rivulata, the most abundant terrapins in the Near and Middle East and South‐east Europe, as model. Their phylogeographies provide evidence that speciation of chelonians fits the allopatric speciation model, with both species being in the parapatric phase of speciation, and that intrinsic isolation mechanisms are developed during speciation. Hybridization between M. caspica and M. rivulata is very rare, suggesting that the increasing numbers of hybrids in other species are caused by human impact on environment (breakdown of ecological isolation). Genetic differentiation within M. caspica and M. rivulata resembles the paradigm of southern genetic richness and northern purity of European biota. However, in west Asia this pattern is likely to reflect dispersal and vicariance events older than the Holocene. For M. caspica three distinct Pleistocene refuges are postulated (Central Anatolia, south coast of Caspian Sea, Gulf of Persia). Morphologically defined subspecies within M. caspica are not supported by genetic data. This is one of the few studies available about the phylogeography of west and central Asian species.

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Section: Phylogeographymentioning

confidence: 97%

Section: Phylogeographymentioning

confidence: 99%

Go east: phylogeographies of Mauremys caspica and M. rivulata– discordance of morphology, mitochondrial and nuclear genomic markers and rare hybridization

Fritz

Ayaz

Buschbom³

et al. 2008

J of Evolutionary Biology

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“…The periodicity of the Hα line has been found on the order of several weeks to years. The best studied photometric periodicity is for MWC 342 (Shevchenko et al 1993;Mel'Nikov 1997;Chkhikvadze et al 2002). It shows a short period between 14 and 16 days, with a longer one around 40 and 120 days.…”

Section: Introductionmentioning

confidence: 99%

First detection of a magnetic field in low-luminosity B[e] stars

Korčáková

Sestito

Manset

et al. 2022

A&A

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We report the first detection of the magnetic field in a star of FS CMa type, a subgroup of objects characterized by the B[e] phenomenon. The split of magnetically sensitive lines in IRAS 17449+2320 determines the magnetic field modulus of 6.2 ± 0.2 kG. Spectral lines and their variability reveal the presence of a B-type spectrum and a hot continuum source in the visible. The hot source confirms GALEX UV photometry. Because there is a lack of spectral lines for the hot source in the visible, the spectral fitting gives only the lower temperature limit of the hot source, which is 50 000 K, and the upper limit for the B-type star of 11 100 K. The V∕R ratio of the Hα line shows quasiperiodic behavior on timescale of 800 days. We detected a strong red-shifted absorption in the wings of Balmer and O I lines in some of the spectra. The absorption lines of helium and other metals show no, or very small, variations, indicating unusually stable photospheric regions for FS CMa stars. We detected two events of material infall, which were revealed to be discrete absorption components of resonance lines. The discovery of the strong magnetic field together with the Gaia measurements of the proper motion show that the most probable nature of this star is that of a post-merger object created after the binary left its birth cluster. Another possible scenario is a magnetic Ap star around Terminal-Age Main Sequence. On the other hand, the strong magnetic field defies the hypothesis that IRAS 17449+2320 is an extreme classical Be star. Thus, IRAS 17449+2320 provides a pretext for exploring a new explanation of the nature of FS CMa stars or, at least, a group of stars with very similar spectral properties.

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Time-dependent spectral-feature variations of stars displaying the B[e] phenomenon

Polster

Korčáková

Votruba

et al. 2013

A&A

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The B[e] phenomenon can be present in stars of different types and at different evolutionary stages. Very extended circumstellar matter prohibits the study of the atmosphere of these stars, since no photospheric lines are usually observed. Standard stellar atmosphere models are thus not applicable when determining stellar parameters. One of a few possibilities for comprehending the nature of these objects is to study their time variations. Unfortunately, almost no set of spectra with an adequate time description is available for these objects. We obtained an extensive set of MWC 342 spectra (102) We detected variability in the spectral lines on both short and long time scales. He i 6678 Å shows day-to-day changes in its line profile. We observed pure absorption, pure emission, the P Cygni profile, and the inverse P Cygni profile in this line. There are time intervals where this line disappeared. The Hα line also shows considerable changes in its line profile, radial velocities, and equivalent widths. A cycle of about 1560 days was detected in its radial velocities. The detailed description of the variations in MWC 342 spectra reveals its important properties. The inner atmosphere is affected by changes of days, while existing long-term waves are propagated into the outer regions. It is highly probable that the continuum radiation in the visual region is also variable. The inverse P Cygni profile was probably observed when the continuum radiation reached its maximum. These properties indicate the complicated nature of this object. We discuss here a possible explanation of the observations by a stellar wind supported by pulsations.

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Cited by 3 publications

References 2 publications

Go east: phylogeographies of Mauremys caspica and M. rivulata– discordance of morphology, mitochondrial and nuclear genomic markers and rare hybridization

Go east: phylogeographies of Mauremys caspica and M. rivulata– discordance of morphology, mitochondrial and nuclear genomic markers and rare hybridization

First detection of a magnetic field in low-luminosity B[e] stars

Time-dependent spectral-feature variations of stars displaying the B[e] phenomenon

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