摘要:

AbstractRestriction fragment length polymorphism (RFLP) analysis of mitochondrial DNA was used to examine the regional population structure of a species of gecko (Oedura reticulata) in vegetation remnants within the Western Australian wheatbelt. The species exhibited considerable polymorphism within and between populations with 22 haplotypes recognized among 12 populations. Phylogenetic analysis of haplotypes and clustering of nucleotide divergence among populations demonstrated little regional structure within the species with several haplotypes present in all three regions surveyed. This contrasted markedly with variation in haplotype frequency among populations which showed a high degree of independence between populations indicating that current levels of maternal gene flow are low and that the populations are too small to prevent genetic drift. This conclusion is supported by generally lower numbers of haplotypes in remnant populations than in nearby nature reserves. These findings, combined with demographic data from a previous study, suggest that post‐fragmentation populations ofO. reticulataare unable to form a metapopulation structure in the habitat that remains and that stochastic extinction forces alone will be sufficient to severely reduce the regional distribution of this species. This study demonstrates that mtDNA is a useful tool for detecting contemporary population phenomena and can provide qualitative information of practical importance to wildlife manager

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00233.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe 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 fromMelomys 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 ec

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00234.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA recently described PCR‐based method for the analysis of intergenic spacer (IGS) length variation in the ribosomal (r) DNA ofDrosophila melanogasterwas used to analyse the distribution of IGS length variants in the rDNA of a number of recently collected D.melanogasterpopulations. One group of populations, from Europe and North Africa, was shown to have low intrapopulation IGS length variation following maintenance of massed populations in the laboratory for an extended period. However, a greater degree of IGS profile variability was detected at a number of levels in the majority of laboratory‐maintained isofemale lines from two of these populations plus a second group of populations which were collected more recently from the eastern coast of Australia; all of which were immediately divided into isofemale lines following collection. Interestingly, PCR analysis of pooled DNA extracts from 30 individuals of either sex showed almost identical PCR profiles from each of the Australian populations. These preliminary results are discussed with regard to the possible combinations of forces (natural selection, neutral drift and genomic molecular drive) on the patterns of IGS length variat

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00235.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIn the south‐western United States and Mexico, mountain sheep were found to have low levels of mtDNA sequence divergence among haplotypes and low overall nucleotide diversity. Potential causes for this low diversity are discussed. Significant differences in mtDNA haplotype distributions over short distances and high values ofNSTon a local scale appear to be a result of the tendency of female mountain sheep to disperse less frequently and over shorter distances than males. A lack of concordance between mtDNA haplotype distributions and assumed subspecies boundaries suggest that some taxonomic labels need to be revise

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00236.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractRacial differentiation and genetic variability were studied between and within the coastal, north interior, and south interior races of Douglas‐fir using RAPD and allozyme markers. Nearly half of all RAPD bands scored (13:45%) were found to be amplified from mitochondrial DNA. They exhibited maternal inheritance among hybrids and back‐crosses between the races, and were much more highly differentiated (GST= 0.62 for haplotype frequencies) than were allozymes (GST= 0.26). No evidence of hybridization or introgression was detected where the coastal and interior races come into proximity in central Ore

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00237.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractRecently, it has been recognized that blackfly populations may host two forms of infection by iridescent viruses (IVs); a covert (inapparent, nonlethal) form which was common in springtime populations in the River Ystwyth, Wales, and a patent (obvious, lethal) form which was rare. This study aimed to investigate the changes in frequency of the two types of infection in blackfly populations over the reproductive period of the flies, April‐September 1992. Blackfly larvae sampled from three different sites along the river were bioassayed for the presence of covert IV infection. Of 870 larvae assayed, 17 were found to be infected. All the infected larvae appeared to beSimnulium variegatum, the dominant species during the sampling period. IV infections were common in the spring (17–37% depending on site) but appeared absent in theS. variegatumpopulation for most of the summer months, reappearing again in the autumn (0–20% infected). These fluctuations were concurrent with biotic and abiotic factors: elevated levels of covert infection occurred at low population densities, high water flow rates, low temperatures (and presumably slower growth rates), although it is not clear if any cause‐and‐effect relationship exists. Patent infections occurred immediately after the peak of covert infection in the spring, and again in the autumn. Virus characterization of isolates from covertly infected larvae showed that three distinct groups of isolates were present in the blackfly population. Isolates from the springtime populations were mostly variants of an isolate found in patently infected blackfly larvae in the 1970s (Aberystwyth IV). Isolates from the autumn populations were mostly variants of an isolate from a patently infected larva found in September the previous year. A third group comprised a single novel isolate which was detected in a covertly infected larva. The mechanisms by which IVs persist in blackfly populations remain unknown, although the role of alternative hosts is a possibility which needs to b

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00238.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractGrape phylloxera,Daktulosphaira vitifoliaeFitch, is a parthenogenetic, aphid‐like pest which attacks the roots and leaves of manyVitisL. species. Feeding on the roots ofV. viniferaL. cultivars leads to decreased plant productivity and eventual death. Isolates of phylloxera have been grouped into ‘biotypes’ based on the aggressiveness of their feeding behaviour, relative reproductive rates, and abilities to cause decline onV. viniferaand the grape rootstock AXR1. The goal of our research was to determine whether these bio‐type definitions were reflected in the genetic diversity among laboratory‐cultured colonies of Californian phylloxera. Thirteen phylloxera isolates, encompassing biotypes A, B and non‐A or ‐B types based on their feeding and reproduction, were analysed using the RAPD‐PCR method. Results indicate that there were genetic differences among isolates and that there was as much polymorphism within biotypes as among biotypes. This is surprising in a parthenogenetic organism and leads us to suggest that there have been multiple introductions of phylloxera into California, that phylloxera are not obligately parthenogenetic, or that there are other mechanisms whereby phylloxera may evolve rel

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00239.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe mitochondrial DNAs of 192 Moroccan and 173 Spanish honey bee colonies were characterized by a rapid test involving the restriction byDraI of a PCR‐fragment of the COI‐COII region. In Morocco, we found eight haplotypes, all characteristic of the African (A) lineage, suggesting that most if not all the maternal lineages of the colonies repeatedly imported from Europe over the last 150 years have not contributed mitochondrial genomes to the local population. Using two new genetic distances analogous to the shared allele distance defined for nuclear genes, we showed that Morocco was most probably colonized by two sublineages, one from the north‐east and the other one from the south of the country and that the contact zone between them extends along both sides of the Atlas range. In Spain, we found eight haplotypes characteristic of lineage A (six in common with Morocco) and four of lineage M (the West European lineage). The distribution of haplotypes of both lineages forms a gradient withc.10% of lineage M in the south of Spain (Seville) and up to 100% in the north (San Sebastian). Three hypotheses are presented to explain the large differences of haplotype frequencies between Moroccan and lineage A Spanish colonies: a non‐Moroccan origin of lineage A in Spain, an ancient Moroccan origin or a recent Moroccan origin with a rapid shift of haplotype frequencies due to a founder

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00240.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractRestriction analysis of mitochondrial DNA (mtDNA) from 204 individuals of swordfish (Xiphias gladius) revealed no differentiation among samples from three sites in the Mediterranean Sea (Greece, Italy, Spain), but a high degree of differentiation between Mediterranean samples and a sample from the Gulf of Guinea. A fifth sample from the Atlantic side of the Straits of Gibraltar (Tarifa) consisted mostly of mitotypes that are common in the Mediterranean, but contained several of mtDNA types of the Guinea sample not found in the Mediterranean. We conclude that, in spite of free migration of swordfish across the Straits of Gibraltar, little genetic exchange occurs between the populations inhabiting the Mediterranean Sea and the tropical Atlantic ocean. This is the first evidence of genetic differentiation among geographic populations of this highly mobile species that supports a world‐wide fisher

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00241.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThenifD—Kintergenic spacer (IGS) ofArI3andACoN24dwere found to have a length 265 and 199 nucleotides, respectively. They are markedly less conserved than the two neighbouring genes and have, in some instances, a repeated structure reminiscent of an insertion event The repeated sequence and the IGSs have no detectable homology with sequences in DNA databanks. The IGS has a stem‐loop structure with a low folding energy, lower than that betweennifHandnifD.No convincing alignment of IGS sequences could be obtained amongFrankiastrains. Only betweenACoN24dandArI3, which belong to the same genomic species, was the alignment good enough to permit detection of a doubly repeated structure. No promoter could be detected in the IGSs. The putativenifKopen reading frame (ORF) in Frankia strainArI3has a length of 1587 nucleotides, starting with a GTG codon, preceded by a ribosome binding site of a structure similar to that ofnifH(GGAGGN7). The codon usage was similar to that of previously sequencedFrankiagenes with a strong bias toward G‐ and C‐ending codons except in the case of glycine where GGT is frequent. Alignment of the threeFrankia nifKsequences (EUN1f; ArI3andACoN24d) with those of other nitrogen‐fixing bacteria permitted detection of a sequence conserved among the threeFrankiastrains but absent in the other sequences. A primer targeted to that region in combination with FGPD807‐85 amplified thenifD—KIGS sequences of allFrankiastrains (except the non‐nitrogen‐fixing Frankia strainsCN3andAgB1‐9) and yet failed to amplify DNA of all other nitrogen–fixing bacteria. Conversely, the failure of primer FGPK700′‐92 to amplifyAlnus‐infective strains could be explained by point mutations i

ISSN:0962-1083    

DOI:10.1111/j.1365-294X.1995.tb00242.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY