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Sökning: WFRF:(Åkesson Susanne) > (2005-2009)

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1.
  • Bensch, Staffan, et al. (författare)
  • Conflicting patterns of mitochondrial and nuclear DNA diversity in Phylloscopus warblers
  • 2006
  • Ingår i: Molecular Ecology. - 0962-1083. ; 15:1, s. 161-171
  • Tidskriftsartikel (refereegranskat)abstract
    • Molecular variation is often used to infer the demographic history of species, but sometimes the complexity of species history can make such inference difficult. The willow warbler, Phylloscopus trochilus, shows substantially less geographical variation than the chiffchaff, Phylloscopus collybita, both in morphology and in mitochondrial DNA (mtDNA) divergence. We therefore predicted that the willow warbler should harbour less nuclear DNA diversity than the chiffchaff. We analysed sequence data obtained from multiple samples of willow warblers and chiffchaffs for the mtDNA cytochrome b gene and four nuclear genes. We confirmed that the mtDNA diversity among willow warblers is low (π = 0.0021). Sequence data from three nuclear genes (CHD-Z, AFLP-WW1 and MC1R) not linked to the mitochondria demonstrated unexpectedly high nucleotide diversity (π values of 0.0172, 0.0141 and 0.0038) in the willow warbler, on average higher than the nucleotide diversity for the chiffchaff (π values of 0.0025, 0.0017 and 0.0139). In willow warblers, Tajima's D analyses showed that the mtDNA diversity, but not the nuclear DNA diversity, has been reduced relative to the neutral expectation of molecular evolution, suggesting the action of a selective sweep affecting the maternally inherited genes. The large nuclear diversity seen within willow warblers is not compatible with processes of neutral evolution occurring in a population with a constant population size, unless the long-term effective population size has been very large (Ne > 106). We suggest that the contrasting patterns of genetic diversity in the willow warbler may reflect a more complex evolutionary history, possibly including historical demographic fluctuations or historical male-biased introgression of nuclear genes from a differentiated population of Phylloscopus warblers.
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2.
  • Bensch, Staffan, et al. (författare)
  • Genetic, morphological, and feather isotope variation of migratory willow warblers show gradual divergence in a ring.
  • 2009
  • Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 18:14, s. 3087-96
  • Tidskriftsartikel (refereegranskat)abstract
    • The circular distribution of the willow warbler Phylloscopus trochilus around the Baltic Sea shares many features with the classic examples of ring species; however, the system is much younger. It has previously been shown that a secondary contact zone is located in central Scandinavia, where there are narrow clines for several morphological traits coincident with a migratory divide. Here we analyse multiple traits and genes from > 1700 males captured on breeding territories at 77 sites spread around the Baltic Sea to test the following hypothesis. If the secondary contact zone in Scandinavia is a result of divergence in two allopatric refuge populations during the last glaciation, we expect to find a similar secondary contact zone somewhere else around the circular distribution. Our results show that the trait clines were wider and displaced from each other along the eastern side of the Baltic Sea. Analyses of 12 microsatellite loci confirmed that the genome is very similar between the terminal forms (F(ST) = 0). Two AFLP-derived markers filtered out from a genomic scan instead appear to be maintained by selection. These markers exhibited steep clines at the secondary contact zone in Scandinavia, but as for the phenotypic traits, had vastly different cline centres east of the Baltic Sea. The trait clines along the ring distribution outside the Scandinavian secondary contact zone thus seem to have been shaped by independent action of selection or drift during the process of postglacial colonization.
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3.
  • Bensch, Staffan, et al. (författare)
  • Patterns of stable isotope signatures in willow warbler Phylloscopus trochilus feathers collected in Africa
  • 2006
  • Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857. ; 37:4, s. 323-330
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • We conducted stable isotope analyses of nitrogen and carbon on feathers obtained from willow warblers in Africa to find an explanation for a previously observed pattern of different delta N-15 and delta C-13 values across a migratory divide in central Scandinavia. A new data set confirms that north Scandinavian birds of the subspecies P. t. acredula have higher delta N-15 values than south Scandinavian birds of the subspecies P. t. trochilus. In Africa, we found significant differences for both delta N-15 and delta C-13 values among feathers collected from major geographical regions as well as between countries within regions. Isotope signatures of delta N-15 and delta C-13 in Scandinavian acredula matched well with those of willow warblers sampled in southern parts of Africa, but differed from samples obtained in East and West Africa. Isotope signatures in Scandinavian trochilus did not agree with the pattern in any of the three African regions (West, East or South). However, a more detailed analysis of the isotopic data in feathers from countries within West Africa, which is the wintering region of Swedish trochilus based on ringing recoveries, revealed a correspondence with samples from Liberia, the Ivory Coast and Nigeria.
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4.
  • Brattström, Oskar, et al. (författare)
  • Effects of wind and weather on red admiral, Vanessa atalanta, migration at a coastal site in southern Sweden
  • 2008
  • Ingår i: Animal Behaviour. - : Elsevier BV. - 1095-8282 .- 0003-3472. ; 76, s. 335-344
  • Tidskriftsartikel (refereegranskat)abstract
    • Each autumn, large numbers of red admirals migrate throughout northern Europe,flying south, to reach areas with conditions suitable for surviving the winter. We observed the visible butterfly migration at Falsterbo peninsula, the southwesternmost point in Sweden, where red admirals are seen most autumns. ying towards the Danish coast on their way to more southern parts of Europe. Weather parameters from a local weather station were used to analyse what factors are important for red admiral migration across the sea. Wind direction was among the important weather variables affecting the initiation of the migratory departure; most other studies of butterfly migration reported no large effect of wind direction. This difference is probably because the butterflies in our study were about to cross open sea for more than 20 km, whereas most previous studies were from inland locations where butterflies could avoid wind effects by. ying close to the ground or on the lee side of topographical features. Other important weather variables affecting red admiral migration at Falsterbo were low wind speed and clear skies. The flight direction at Falsterbo was towards the west, which is in contrast to the southward direction generally reported during autumn migration in this species. This is probably because the red admirals followed both the local topography and the closest route to land on the other side and therefore deviated from the normally preferred direction to minimize flight over open water. (c) 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
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5.
  • Brattström, Oskar, et al. (författare)
  • Placing butterflies on the map - testing regional geographical resolution of three stable isotopes in Sweden using the monophagus peacock Inachis io
  • 2008
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 31:4, s. 490-498
  • Tidskriftsartikel (refereegranskat)abstract
    • Stable isotope analyses of tissues have been used to help delineate natal regions and routes of migratory animals. The foundations of such studies are isotopic gradients or differences representing geographic regions and habitat used by the organism that are retained in selected tissues. We sampled peacock butterflies Inachis io on a regional level in southern Sweden to study natural variation and the resolving power of the stable isotope method to delineate individuals from known areas on a smaller scale than has typically been used in previous studies. Hydrogen (delta D), carbon (delta C-13) and nitrogen (delta N-15) isotopes were obtained from butterflies at seven different locations in an area of 250x250 km over three years (2002-2004). We found sufficient isotopic differences on this regional scale to delineate approximate origins. Of the three isotopes, deuterium showed good discrimination between sites, carbon isotopes showed weaker differentiation, whereas nitrogen isotopes proved unsuitable for small scale studies in this region due to high and unpredictable variation. We found there was enough variation in delta D between years to prevent a general application of the technique to resolve sub-regional variation. Substantial part of this variation was probably caused by seasonal changes in delta D of precipitation. These differences produce significant variation in delta D between years in animals having short and variable tissue development times, and are difficult to estimate in natural situations. We conclude that stable isotopes are potentially powerful predictors for studies of migratory butterflies in Europe. However, without good knowledge about the sampled individuals' previous life-history, a lot of the natural environmental variation in tissue delta D cannot be controlled for. In the case of migratory species, this information is difficult to obtain, making the confidence intervals for prediction of natal areas fairly wide and probably only suitable for longer distance migration.
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6.
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7.
  • Hegedues, Ramon, et al. (författare)
  • Polarization patterns of thick clouds: overcast skies have distribution of the angle of polarization similar to that of clear skies
  • 2007
  • Ingår i: Journal of the Optical Society of America A. - 1084-7529. ; 24:8, s. 2347-2356
  • Tidskriftsartikel (refereegranskat)abstract
    • The distribution of polarization in the overcast sky has been practically unknown. Earlier the polarization of light from heavily overcast skies (when the Sun's disc was invisible) has been measured only sporadically in some celestial points by point-source polarimetry. What kind of patterns of the degree p and angle a of linear polarization of light could develop after transmission through a thick layer of ice or water clouds? To answer this question, we measured the p and a patterns of numerous totally overcast skies on the Arctic Ocean and in Hungary by full-sky imaging polarimetry. We present here our finding that depending on the optical thickness of the cloud layer, the pattern of a of light transmitted through the ice or water clouds of totally overcast skies is qualitatively the same as the a pattern of the clear sky. Under overcast conditions the value of a is determined predominantly by scattering on cloud particles themselves. Nevertheless, the degrees of linear polarization of light from overcast skies were rather low (p <= 16 %). Our results obtained under overcast conditions complete the earlier findings that the a pattern of the clear sky also appears in partly cloudy, foggy, and smoky skies. Our results show that the celestial distribution of the direction of polarization is a very robust pattern being qualitatively always the same under all possible sky conditions. This is of great importance for the orientation of polarization-sensitive animals based on sky polarization under conditions when the Sun is not visible. (c) 2007 Optical Society of America.
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8.
  • Hegedus, R, et al. (författare)
  • Anomalous celestial polarization caused by forest fire smoke: why do some insects become visually disoriented under smoky skies?
  • 2007
  • Ingår i: Applied Optics. - 2155-3165. ; 46:14, s. 2717-2726
  • Tidskriftsartikel (refereegranskat)abstract
    • The effects of forest fire smoke on sky polarization and animal orientation are practically unknown. Using full-sky imaging polarimetry, we therefore measured the celestial polarization pattern under a smoky sky in Fairbanks, Alaska, during the forest fire season in August 2005. It is quantitatively documented here that the celestial polarization, a sky attribute that is necessary for orientation of many polarization-sensitive animal species, above Fairbanks on 17 August 2005 was in several aspects anomalous due to the forest fire smoke: (i) The pattern of the degree of linear polarization p of the reddish smoky sky differed considerably from that of the corresponding clear blue sky. (ii) Due to the smoke, p of skylight was drastically reduced (p(max) <= 14%, p(average) <= 8%). (iii) Depending on wavelength and time, the Arago, Babinet, and Brewster neutral points of sky polarization had anomalous positions. We suggest that the disorientation of certain insects observed by Canadian researchers under smoky skies during the forest fire season in August 2003 in British Columbia was the consequence of the anomalous sky polarization caused by the forest fire smoke.
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9.
  • Hegedus, R, et al. (författare)
  • Could Vikings have navigated under foggy and cloudy conditions by skylight polarization? On the atmospheric optical prerequisites of polarimetric Viking navigation under foggy and cloudy skies
  • 2007
  • Ingår i: Royal Society of London. Proceedings A. Mathematical, Physical and Engineering Sciences. - : The Royal Society. - 1364-5021. ; 463:2080, s. 1081-1095
  • Tidskriftsartikel (refereegranskat)abstract
    • In sunshine, the Vikings navigated on the open sea using sundials. According to a widespread hypothesis, when the Sun was occluded by fog or clouds the Vikings might have navigated by skylight polarization detected with an enigmatic birefringent crystal (sunstone). There are two atmospheric optical prerequisites for this alleged polarimetric Viking navigation under foggy/cloudy skies: (1) the degree of linear polarization p of skylight should be high enough and (2) at a given Sun position, the pattern of the angle of polarization a of the foggy/cloudy sky should be similar to that of the clear sky. Until now, these prerequisites have not been investigated. Using full-sky imaging polarimetry, we measured the p- and a-patterns of Arctic foggy and cloudy skies when the Sun was invisible. These patterns were compared with the polarization patterns of clear Arctic skies. We show here that although prerequisite (2) is always fulfilled under both foggy and cloudy conditions, if the fog layer is illuminated by direct sunlight, prerequisite (1) is usually satisfied only for cloudy skies. In sunlit fog, the Vikings could have navigated by polarization only, if p of light from the foggy sky was sufficiently high.
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10.
  • Hegedus, R, et al. (författare)
  • Polarization of "water-skies" above arctic open waters: how polynyas in the ice-cover can be visually detected from a distance
  • 2007
  • Ingår i: Journal of the Optical Society of America A. - 1084-7529. ; 24:1, s. 132-138
  • Tidskriftsartikel (refereegranskat)abstract
    • The foggy sky above a white ice-cover and a dark water surface (permanent polynya or temporary lead) is white and dark gray, phenomena called the "ice-sky" and the "water-sky," respectively. Captains of icebreaker ships used to search for not-directly-visible open waters remotely on the basis of the water sky. Animals depending on open waters in the Arctic region may also detect not-directly-visible waters from a distance by means of the water sky. Since the polarization of ice-skies and water-skies has not, to our knowledge, been studied before, we measured the polarization patterns of water-skies above polynyas in the arctic ice-cover during the Beringia 2005 Swedish polar research expedition to the North Pole region. We show that there are statistically significant differences in the angle of polarization between the water-sky and the ice-sky. This polarization phenomenon could help biological and man-made sensors to detect open waters not directly visible from a distance. However, the threshold of polarization-based detection would be rather low, because the degree of linear polarization of light radiated by water-skies and ice-skies is not higher than 10%. (c) 2006 Optical Society of America.
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