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61.
Abstract. Species composition patterns and vegetation-environment relationships were quantified for high-elevation rock outcrops of the Southern Appalachian Mountains, an infrequent and insular habitat in a forested landscape. Outcrops occur over a wide geographic range encompassing extensive variation in both geology and climate. Geographic-scale factors interact with site-scale factors to produce variation in vegetation among outcrops. Similarly, site-scale factors interact with micro-scale factors to produce variation in vegetation within outcrops. To provide a quantitatively-based classification of outcrop vegetation we used a TWINSPAN analysis of 154 100-m2 plots. We recognized nine communities that primarily correspond to different combinations of elevation, bedrock type, geography, and moisture. Within outcrops of a single bedrock type, vegetation composition of 100-m2 plots was consistently correlated with elevation and solar radiation, but relationships to soil nutrients varied with bedrock type. Both site-scale (100 m2) factors (e.g. elevation, slope, aspect, and bedrock type) and plot-scale (1-m2) microsite factors (e.g. soil depth, vegetation height, soil nutrients) were strongly correlated with species composition at the 1-m2 level. Environment can be used to predict composition more effectively for 100-m2 plots on a single bedrock type than either across bedrock types or at a 1-m2 scale. Composition-environment relationships resemble those described for outcrop systems from other regions with pronounced topographic relief more than they do those described for the nearby but flatter and lower-elevation outcrops of the Southeastern Piedmont. There is strong spatial autocorrelation in this community, perhaps owing to dispersal limitation. Consequently, a comprehensive conservation strategy must include reservation of both a range of geologic types and a range of geographic locations. 相似文献
62.
The use of the isoenzymic marker gene Got-1 in the recognition of incompatibility S alleles in apple
I. Batlle F. H. Alston K. M. Evans 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,90(2):303-306
The S incompatibility system of apple was confirmed through the application of the gene Got-1 for glutamate oxaloacetate transaminase as a marker for the S locus. The 11S alleles proposed by Kobel et al. (1939) were confirmed through anomalous segregations for Got-1 observed in 14 semi-compatible crosses and regular segregations observed in 2 fully compatible crosses. The S allele genotypes of Idared (S
3
S
7), Cox (S
5
S
9) and Fiesta (S
3
S
5) were determined and found to fall within the original series. By associating parental incompatibility genotypes with the segregation of Got-1 alleles, we were able to deduce the coupling of S and Got-1 alleles in 9 varieties. 相似文献
63.
An integrated genetic linkage map for eucalypts using RFLP,RAPD and isozyme markers 总被引:19,自引:0,他引:19
M. Byrne J. C. Murrell B. Allen G. F. Moran 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,91(6-7):869-875
An integrated genetic linkage map for E. nitens was constructed in an outbred three-generation pedigree. Analysis of 210 RFLP, 125 RAPD and 4 isozyme loci resulted in 330 markers linked in 12 linkage groups covering 1462 cM (n=11 in eucalypts). The 12th linkage group is comprised of only 5 markers and will probably coalesce with another linkage group when further linked loci are located. Co-dominant RFLP loci segregating in both parents were used to integrate linkages identified in the male and female parents. Differences in recombination frequencies in the two parents were observed for a number of pairs of loci, and duplication of sequences was identified both within and between linkage groups. The markers were distributed randomly across the genome except for the RFLPs in linkage group 10 and for some loci showing segregation distortion, which were clustered into three regions of the map. The use of a large number of co-dominant RFLP loci in this map enables it to be used in other pedigrees of E. nitens and forms a basis for the detection and location of QTL in E. nitens and other eucalypt species. 相似文献
64.
Structural evolution of wheat chromosomes 4A, 5A,and 7B and its impact on recombination 总被引:3,自引:3,他引:0
K. M. Devos J. Dubcovsky J. Dvořák C. N. Chinoy M. D. Gale 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,91(2):282-288
The construction of comparative genetic maps of chromosomes 4Am and 5Am of Triticum monococcum and chromosomes of homoeologous groups 4, 5 and 7 of T. aestivum has provided insight into the evolution of these chromosomes. The structures of chromosomes 4A, 5A and 7B of modern-day hexaploid bread wheat can be explained by a 4AL/5AL translocation that occurred at the diploid level and is present both in T. monococcum and T. aestivum. Three further rearrangements, a 4AL/7BS translocation, a pericentric inversion and a paracentric inversion, have taken place in the tetraploid progenitor of hexaploid wheat. These structural rearrangements and the evolution of chromosomes 4A, 5A and 7B of bread wheat are discussed. The presence of the 4AL/5AL translocation in several Triticeae genomes raises two questions — which state is the more primitive, and is the translocation of mono- or poly-phylogenetic origin? The rearrangements that have occurred in chromosome 4A resulted in segments of both arms having different positions relative to the telomere, compared to 4Am and to 4B and 4D. Comparisons of map length in these regions indicate that genetic length is a function of distance from the telomere, with the distal regions showing the highest recombination. 相似文献
65.
E. Nevo V. Kirzhner A. Beiles A. Korol 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1997,352(1351):381-389
Our data on a subterranean mammal, Spalax ehrenbergi, and other evidence, indicate that appreciable polymorphism can be preserved in small isolated populations consisting of several dozens of, or a hundred, individuals. Current theoretical models predict fast gene fixation in small panmictic populations without selection, mutation, or gene inflow. Using simple multilocus models, we demonstrate here that moderate stabilizing selection (with stable or fluctuating optimum) for traits controlled by additive genes could oppose random fixation in such isolates during thousands of generations. We also show that in selection-free models polymorphism persists only for a few hundred generations even under high mutation rates. Our multi-chromosome models challenge the hitchhiking hypothesis of polymorphism maintenance for many neutral loci due to close linkage with few selected loci. 相似文献
66.
The available amino acid sequences of the α-amylase family (glycosyl hydrolase family 13) were searched to identify their
domain B, a distinct domain that protrudes from the regular catalytic (β/α)8-barrel between the strand β3 and the helix α3. The isolated domain B sequences were inspected visually and also analyzed
by Hydrophobic Cluster Analysis (HCA) to find common features. Sequence analyses and inspection of the few available three-dimensional
structures suggest that the secondary structure of domain B varies with the enzyme specificity. Domain B in these different
forms, however, may still have evolved from a common ancestor. The largest number of different specificities was found in
the group with structural similarity to domain B from Bacillus cereus oligo-1,6-glucosidase that contains an α-helix succeeded by a three-stranded antiparallel β-sheet. These enzymes are α-glucosidase,
cyclomaltodextrinase, dextran glucosidase, trehalose-6-phosphate hydrolase, neopullulanase, and a few α-amylases. Domain B
of this type was observed also in some mammalian proteins involved in the transport of amino acids. These proteins show remarkable
similarity with (β/α)8-barrel elements throughout the entire sequence of enzymes from the oligo-1,6-glucosidase group. The transport proteins, in
turn, resemble the animal 4F2 heavy-chain cell surface antigens, for which the sequences either lack domain B or contain only
parts thereof. The similarities are compiled to indicate a possible route of domain evolution in the α-amylase family.
Received: 4 December 1996 / Accepted: 13 March 1997 相似文献
67.
利用Oligo1000DNA合成仪(Beckman)合成了长度为45bp的寡核苷酸单链,经纯化后用同位素γ-32P-ATP作5′末端标记后,制备成鱼类LZF-IDNA指纹探针。通过对鱼类的群体实验、亲子鉴定实验、组织细胞的稳定性实验和鱼类种类的适用范围实验后,测得:(1)LZF-IDNA指纹探针属多位点寡核苷酸探针;(2)LZF-IDNA指纹探针在鱼类种群中的鉴别机率为9.23×10-16;(3)LZF-IDNA指纹探针在鱼类亲子鉴定实验中的父系概率为0.999962;(4)LZF-IDNA指纹探针,是一种稳定的,既具有个体识别能力,又具有一定种属特异性的、适用于鱼类DNA指纹图研究的基因指纹探针。 相似文献
68.
N. J. H. CAMPBELL F. C. HARRISS M. S. ELPHINSTONE P. R. BAVERSTOCK 《Molecular ecology》1995,4(4):407-418
The ability of DNA screening techniques such as Temperature Gradient Gel Electrophoresis (TGGE) and Heteroduplex Analysis to provide resolution approaching that provided by DNA sequencing for a fraction of the time, effort and expense point to them as the logical successor to allozyme electrophoresis for population genetics. Here we present a novel alternative to the standard TGGE/Heteroduplex Analysis protocol - Outgroup Heteroduplex Analysis (OHA). We assess this technique's sensitivity in comparison to previous screening approaches using a known hierarchy of sequence differences. Our data show that Outgroup Heteroduplex Analysis has greatly increased sensitivity for screening DNA variants from that of TGGE used alone and is easily applicable to large numbers of samples. Using this technique we can consistently detect differences of as small as one base change in a 433-base-pair fragment of Control Region mitochondrial DNA from Melomys cerbinipes (an Australian rodent). The approach should easily be extendable to nuclear loci and is not necessarily dependent on the use of a denaturing gradient When combined with a targeted sequencing effort, OHA provides a sensitive and simple means of obtaining allele/haplotype frequencies and their phylogenies for population and phylogeographic studies in molecular ecology. 相似文献
69.
70.
S. H. Mahmoud J. A. Gatehouse D. Boulter 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1984,68(6):559-566
Summary Three isoenzyme systems (amylase, esterase and glutamate oxaloacetate transaminase) were examined in seeds of pea (Pisum sativum L.) and shown to give clear variation in their band patterns on gel electrophoresis between different lines. The inheritance of these isoenzyme systems, and the location of their genes on the pea genome was investigated. Reciprocal crosses were made between lines, F2 seeds were analysed for segregation in the band patterns of the isoenzymes, and F2 plants were investigated to find linkage between the genes for these isoenzymes and genes for selected morphological markers. The results obtained showed that each of the investigated isoenzyme systems is genetically controlled by co-dominant alleles at a single locus. The gene for amylase was found to be on chromosome 2, linked to the loci k and wb (wb ... 9 ... k ... 25 ... Amy). The gene for esterase was found to be linked with the gene Br (chromosome 4) but the exact location is uncertain because of the lack of the morphological markers involved in the cross. The gene for glutamate oxaloacetate transaminase was found to be on chromosome 1 and linked with the loci a and d (a... 24... Got... 41 ... d). 相似文献