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161.
Aim Late Pleistocene ice sheets are thought to have covered most of western Canada, including all of British Columbia (BC). We examine patterns of genetic variation in an Arctic–alpine plant to evaluate the possibility of full glacial refugia within the area covered by the Cordilleran ice sheet (CIS) and to uncover post-glacial migration routes.
Location Western North America.
Methods We sampled 1030 individuals of the Arctic–alpine plant Oxyria digyna from 117 populations distributed over much of its range in western and northern North America. DNA haplotypes were identified using restriction site analysis of two chloroplast DNA intergene spacer regions, psb A- trn H and trn T-L. We examined the geographical distribution of haplotype diversity in relation to latitude, and also compared various indices of diversity in putatively glaciated and unglaciated regions. Patterns of migration were inferred using nested clade analysis.
Results We detected a total of 20 haplotypes. High haplotype diversity was found in Beringia, in unglaciated western USA, and in northern BC at 57–59° N, well within the accepted limits of the CIS. Ancestral haplotypes were also centred in northern BC.
Main conclusions High genetic diversity of Oxyria digyna is expected in unglaciated regions, but unexpected in northern BC if British Columbia was entirely covered by ice during the late Pleistocene. Our observations suggest the presence of unglaciated areas providing late Pleistocene refugia in northern BC. Such refugia would have important implications for the origins and migrations of many plant and animal species in north-western North America. 相似文献
Location Western North America.
Methods We sampled 1030 individuals of the Arctic–alpine plant Oxyria digyna from 117 populations distributed over much of its range in western and northern North America. DNA haplotypes were identified using restriction site analysis of two chloroplast DNA intergene spacer regions, psb A- trn H and trn T-L. We examined the geographical distribution of haplotype diversity in relation to latitude, and also compared various indices of diversity in putatively glaciated and unglaciated regions. Patterns of migration were inferred using nested clade analysis.
Results We detected a total of 20 haplotypes. High haplotype diversity was found in Beringia, in unglaciated western USA, and in northern BC at 57–59° N, well within the accepted limits of the CIS. Ancestral haplotypes were also centred in northern BC.
Main conclusions High genetic diversity of Oxyria digyna is expected in unglaciated regions, but unexpected in northern BC if British Columbia was entirely covered by ice during the late Pleistocene. Our observations suggest the presence of unglaciated areas providing late Pleistocene refugia in northern BC. Such refugia would have important implications for the origins and migrations of many plant and animal species in north-western North America. 相似文献
162.
To evaluate breastfed infants' responses to scented objects, we videotaped
the facial and bodily reactions of sixty-three infants as they explored, in
succession, three toys that were identical in appearance but different in
their characteristic odor. Two of the toys were scented with odorants
previously shown to be transmitted to human milk, one with ethanol and the
other with vanilla, whereas the third toy was unscented. Each videotape was
subjected to frame-by-frame analysis to measure a variety of behaviors that
are considered either to be exploratory in nature in that they lead to
perceptual information about the object or to reflect the infants' hedonic
reaction. Analyses of these behaviors revealed that the infants looked more
and vocalized less in the presence of the vanilla-scented toy and spent
less time manipulating the ethanol-scented toy when compared with the
unscented toy. Moreover, differential exposure to the odors of ethanol and
vanilla, as indicated by differential consumption of alcohol by a parent or
use of vanilla-scented product by the mother, was related to differential
responses to these odors. These findings suggest that human infants are
able to detect and retain information about the chemical features of their
environment.
相似文献
163.
164.