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Southernmost Populations (southernmost + population)
Selected AbstractsPatterns of isozyme variation as indicators of biogeographic history in Pilgerodendron uviferum (D. Don) FlorínDIVERSITY AND DISTRIBUTIONS, Issue 2 2002A. C. Premoli Abstract. The effects of Pleistocene glaciations on the genetic characteristics of the most austral conifer in the world, Pilgerodendron uviferum, were analysed with specific reference to the hypothesis that the species persisted locally in ice-free areas in temperate South America. It was expected that genetic variation would decrease with latitude, given that ice fields were larger in southern Patagonia and thus refugia were probably located towards the northern distributional limit of the species as suggested by the fossil record. In addition, an increase in among-population genetic divergence was expected with increasing distance to putative glacial refugia. We examined the relationship between location and within-population variability indices of 20 Pilgerodendron populations derived from isozyme analyses. We analysed possible refugia hypotheses by the distribution of allele frequencies using multivariate discriminant analysis. The degree of genetic differentiation with geographical distance between all population pairs was investigated by Mantel tests. Results indicated that Pilgerodendron populations are highly monomorphic, probably reflecting past population bottlenecks and reduced gene flow. Southernmost populations tend to be the least genetically variable and were therefore probably more affected by glacial activity than northern ones. Populations located outside ice limits seem to have been isolated during the glacial period. The presence of centres of genetic diversity, together with the lack of a significant correlation between genetic and geographical distances and the absence of geographical patterns of allelic frequencies at most analysed alleles, may indicate that Pilgerodendron did not advance southward after the last glaciation from a unique northern refugium, but spread from several surviving populations in ice-free areas in Patagonia instead. [source] Temperature-induced plasticity at cellular and organismal levels in the lizard Anolis carolinensisINTEGRATIVE ZOOLOGY (ELECTRONIC), Issue 3 2010Rachel M. GOODMAN Abstract Among ectotherms, individuals raised in cooler temperatures often have larger body size and/or larger cell size. The current study tested whether geographic variation in cell size and plasticity for cell size exist in a terrestrial, ectothermic vertebrate, Anolis carolinensis Voigt, 1832. We demonstrated temperature-induced plasticity in erythrocytes and epithelial cells of hatchlings lizards derived from the eggs of females sampled from four populations and incubated at multiple temperatures. Larger cells were produced in hatchlings from cooler treatments; however, hatchling body size was unaffected by temperature. Therefore, temperature-induced plasticity applies at the cellular, but not organismal, level in A. carolinensis. In addition, reaction norms for cell size differed among populations. There was a latitudinal trend in cell size and in plasticity of cell size among our study populations. The two southernmost populations showed plasticity in cell size, whereas the two northernmost ones did not. We suggest that selection pressure for larger cell size in northern, cooler environments has restricted plasticity in A. carolinensis applied at the cellular level in response to variable incubation environments. [source] Consistent geographic structure among multiple nuclear sequences and cpDNA polymorphisms of Cardamine nipponica Franch. et Savat. (Brassicaceae)MOLECULAR ECOLOGY, Issue 13 2008HAJIME IKEDA Abstract Molecular phylogeography has inferred the history of differentiation between regions and/or among populations following the Pleistocene climatic oscillations, mostly based on the genetic structure of organelle DNA. However, such genetic structure only reflects the history of a single gene, and studies based on single-copy genes of nuclear DNA (nDNA) are required for phylogeography, although their efficiency remains unclear. To examine the utility of nDNA loci, the genetic structures of three genes from Cardamine nipponica, which is closely related to the model species Arabidopsis thaliana, were elucidated: the nDNA genes DET1, PHYA, PHYE, as well as chloroplast DNA (cpDNA). In 279 individuals collected from throughout the range of the species, strong genetic differentiation between northern and central Japan was found for all loci. This result suggested that populations in central Japan experienced a different history from those in northern Japan during the Pleistocene climatic oscillations. In addition, the evidence of refugia at the edges of the distribution, where the genetic structure was less influenced by colonization following range expansion, was shown for several loci. The specific genetic structure within the southernmost populations of northern Japan suggested that this region was also isolated during range expansion. Hence, the consistent history among loci and a more detailed history from several loci indicated that cpDNA can represent the history of vicariance and demonstrated the efficiency of single-copy nuclear genes in phylogeography. [source] Population structure and phylogeography of Solanum pimpinellifolium inferred from a nuclear geneMOLECULAR ECOLOGY, Issue 7 2004Ana Lucía Caicedo Abstract Phylogeographical studies are emerging as a powerful tool for understanding the population structure and evolution of wild relatives of crop species. Because of their value as genetic resources, there is great interest in exploring the distribution of variation in wild relatives of cultivated plants. In this study, we use sequence variation from the nuclear gene, fruit vacuolar invertase (Vac), to investigate the population history of Solanum pimpinellifolium. Solanum pimpinellifolium is a close relative of the cultivated tomato and has repeatedly served as a source of valuable traits for crop improvement. We sequenced the second intron of the Vac gene in 129 individuals, representing 16 populations from the northern half of Peru. Patterns of haplotype sharing among populations indicate that there is isolation by distance. However, there is no congruence between the geographical distribution of haplotypes and their genealogical relationships. Levels of outcrossing decrease towards the southernmost populations, as previously observed in an allozyme study. The geographical pattern of Vac variation supports a centre of origin in northern Peru for S. pimpinellifolium and a gradual colonization along the Pacific coast. This implies that inbreeding populations are derived from outcrossing ones and that variation present at the Vac locus predates the spread of S. pimpinellifolium. The expansion of cities and human agricultural activity in the habitat of S. pimpinellifolium currently pose a threat to the species. [source] Hydraulic adjustment of Scots pine across EuropeNEW PHYTOLOGIST, Issue 2 2009J. Martínez-Vilalta Summary ,,The variability of branch-level hydraulic properties was assessed across 12 Scots pine populations covering a wide range of environmental conditions, including some of the southernmost populations of the species. The aims were to relate this variability to differences in climate, and to study the potential tradeoffs between traits. ,,Traits measured included wood density, radial growth, xylem anatomy, sapwood- and leaf-specific hydraulic conductivity (KS and KL), vulnerability to embolism, leaf-to-sapwood area ratio (AL : AS), needle carbon isotope discrimination (,13C) and nitrogen content, and specific leaf area. ,,Between-population variability was high for most of the hydraulic traits studied, but it was directly associated with climate dryness (defined as a combination of atmospheric moisture demand and availability) only for AL : AS, KL and ,13C. Shoot radial growth and AL : AS declined with stand development, which is consistent with a strategy to avoid exceedingly low water potentials as tree size increases. In addition, we did not find evidence at the intraspecific level of some associations between hydraulic traits that have been commonly reported across species. ,,The adjustment of Scots pine's hydraulic system to local climatic conditions occurred primarily through modifications of AL : AS and direct stomatal control, whereas intraspecific variation in vulnerability to embolism and leaf physiology appears to be limited. [source] High mountains of the Japanese archipelago as refugia for arctic,alpine plants: phylogeography of Loiseleuria procumbens (L.) Desvaux (Ericaceae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009HAJIME IKEDA According to previous phylogeographic studies, high mountains at low latitudes are important areas for the study of the evolutionary history of arctic,alpine plants in surviving the Pleistocene climatic oscillations. To evaluate this hypothesis, we elucidated the genetic structure of the arctic,alpine plant, Loiseleuria procumbens, in the Japanese archipelago, which corresponds to one of the southernmost limits of its distribution, using 152 individuals from 17 populations that covered the entire distribution of the Japanese archipelago and Sakhalin, in addition to samples from Sweden. Based on 854 bp of chloroplast DNA, we detected eight haplotypes. Along with haplotype distribution, strong genetic differentiation between populations in central and northern Japan was elucidated by a neighbour-joining tree (100%) and spatial analysis of molecular variance (79%), which is consistent with other alpine plants in Japan, regardless of the species' range. In addition, the southernmost populations from northern Japan showed specific genetic structure, although the remaining areas of northern Japan and Sakhalin harboured an homogenous genetic structure. Our results suggest that the populations in central Japan persisted for a long time during the Pleistocene climatic oscillation and that genetic divergence occurred in situ, supporting our hypothesis in conjunction with a previous study of another arctic,alpine plant, Diapensia lapponica subsp. obovata. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 403,412. [source] | ||||||||||