bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular evidence for mating asymmetry and female choice in a pocket gopher (Thomomys) hybrid zone
Authors: PATTON J.L. , SMITH M.F. 
Published: April 2008

AbstractThis paper presents circumstantial evidence that the mating system of the North American pocket gophers (Rodentia: Geomyidae) is a promiscuous one, with female choice at its base. A molecular marker (a length variant in the mitochondrial Control region [D‐loop]) is used to show mating asymmetry in a hybrid zone between the species Thomomys bottae and Thomomys townsendii in north‐eastern California. All hybrids result from a bottae mother ×townsendii father cross. Because of significant differences in body size and resulting burrow diameter, bottae females must have actively sought their respective townsendii mates for the asymmetry in mating to have occurred, signalling female choice in these subterranean mammals that are otherwise characterized by exclusive‐use territories, skewed adult sex ratio in favour of females, and high variance in male reproductive success.
Plasmid dynamics in a model soil column
Authors: Sun L. , BAZIN M. J. , LYNCH J. M. 
Published: April 2008

AbstractContinuous‐flow column reactors were used to study the dynamics of plasmid exchange in a structured, thermodynamically open system containing either Enterobacter cloacae or Pseudomonas cepacia, both carrying the transmissible recombinant plasmid R388::Tn1721. Plasmid transfer rates were higher in vermiculite and sterile soil columns supplied with nutrient solution than those in sterile and non‐sterile soil columns without input of nutrient solution. For both species, donor and recipient strains took about 5 days to reach their maximum densities in effluents from the columns supplied with nutrient solution. After about 8 day s the donor and transconjugant populations of P. cepacia in the effluent solution decreased exponentially, whereas E. cloacae donor, recipient and transconjugant strains maintained steady‐state concentrations. The difference between plasmid stability in the two species may have significant consequences in terms of releasing plasmid‐bearing genetically modified microorganisms into the natural environment. The plasmid is persistent in E. cloacae in non‐sterile soil even though its transfer to the marked recipient in non‐sterile soil was minimal.
Distribution of streptothricin acetyltransferase encodi determinants among environmental bacteria
Authors: SMALLA K. , PRAGER R. , ISEMANN M. , PUKALL R. , TIETZE E. , ELSAS J. D. VAN , TSCHÄPE H. 
Published: April 2008

AbstractIn this paper we report about a screening for streptothricin‐ (St)‐resistant phenotypes and genotypes among environmental bacteria from a St virgin area. St‐resistant bacteria were isolated from river water, sewage, manure and soil by selective plating. The resistance quotient was typical of an area without selective pressure. The occurrence of streptothricin acetyltransferase‐encoding determinants and their localization on a Tn7‐like transposon was tested by the application of a set of gene probes. Sat genes could be detected in 22.5% of the tested St‐resistant bacteria but in 100% of the checked Enterobacteriaceae. However, we could not detect sat genes in St‐resistant bacteria from soil samples. Surprisingly the sat genes were found to be located on conjugative or mobilizable plasmids for a rather high number of strains. The determined plasmid species and their restriction patterns showed a high degree of similarities to those observed from an area of strong selective pressure.
Plasmid and chromosomally encoded luminescence marker systems for detection of Pseudomonas fluorescens in soil
Authors: AMIN‐HANJANI S. , MEIKLE A. , GLOVER L. A. , PROSSER J. I. , KILLHAM K. 
Published: April 2008

AbstractLuminescent strains of Pseudomonas fluorescens 10586 were constructed in which luciferase production was constitutive by introduction of Vibrio fischeri luxABE genes on the chromosome and on a multicopy plasmid. Light production in liquid batch culture was directly proportional to biomass concentration during exponential growth and enabled detection by luminometry of 1.7 × 103 and 8.9 × 104 cells/ml for the plasmid and chromosomally marked strains, respectively. Luminescent colonies of both strains were detectable by eye, enabling viable cell enumeration on solid media against a background of non‐luminescent strains. Following inoculation into sterile and non‐sterile soil lower levels of detection were increased but detection of 8.1–59 × 103and 2.2–30 × 103 cells per g of soil was possible for plasmid and chromosomally marked strains. Maximum specific growth rate in liquid culture was unaffected by introduction of lux marker genes on the chromosome, but was reduced in the plasmid marked strain. The chromosomally encoded marker was stable in both liquid culture and in soil, but the plasmid was unstable during continuous subculturing in liquid medium and during growth in soil. The chromosomally encoded luminescence‐marker system therefore provides a convenient, non‐extractive technique for quantification of genetically modified soil microbial inocula.
Typing of artiodactyl MHC‐DRB genes with the help of intronic simple repeated DNA sequences
Authors: SCHWAIGER F.W. , BUITKAMP J. , WEYERS E. , EPPLEN J.T. 
Published: April 2008

AbstractAn efficient oligonucleotide typing method for the highly polymorphic MHC‐DRB genes is described for artiodactyls like cattle, sheep and goat. By means of the polymerase chain reaction, the second exon of MHC‐DRB is amplified as well as part of the adjacent intron containing a mixed simple repeat sequence. Using this primer combination we were able to amplify the MHC‐DRB exons 2 and adjacent introns from all of the investigated 10 species of the family of Bovidae and giraffes. Therefore, the DRB genes of novel artiodactyl species can also be readily studied. Oligonucleotide probes specific for the polymorphisms of ungulate DRB genes are used with which sequences differing in at least one single base can be distinguished. Exonic polymorphism was found to be correlated with the allele lengths and the patterns of the repeat structures. Hence oligonucleotide probes specific for different simple repeats and polymorphic positions serve also for typing across species barriers. The strict correlation of sequence length and exonic polymorphism permits a preselection of specific oligonucleotides for hybridization. Thus more than 20 alleles can already be differentiated from each of the three species.
Detection of highly polymorphic microsatellite loci in a species with little allozyme polymorphism
Authors: HUGHES C. R. , QUELLER D. C. 
Published: April 2008

AbstractMicrosatellite loci are regions of DNA containing tandem repeats of a short sequence motif; they occur abundantly in all eukaryotic genomes and have been shown to be a rich source of highly polymorphic genetic markers in humans and other mammals. These loci are particularly suitable for population studies because they can be relatively easily scored using a combination of polymerase chain reaction (PCR) amplification of each locus followed by electrophoresis to separate alleles. This paper details a method for finding these loci in any species. This method demonstrates that trinucleotide microsatellite loci are abundant and highly polymorphic in the social wasp Polistes annularis, whereas allozyme electrophoresis reveals very little polymorphism. The first six loci examined were all polymorphic with a mean observed heterozygosity of 0.62; in comparison average heterozygosity of 33 allozymes was 0.035. We suggest that this method can be used to detect variation where other methods have failed, making it an ideal tool for population and conservation geneticists who must deal with populations lacking other types of genetic variability.
Scientific principles for ecologically based risk assessment of transgenic organisms
Authors: REGAL P. J. 
Published: April 2008

AbstractIt is critical to base scientific risk assessment of genetically engineered organisms (GEOs) on appropriate scientific concepts. A variety of ‘generic safety’ models has now largely been recognized to have been based on outdated scientific thinking. One broad safety argument that is still used is that genetic engineering categorically is nothing but an extension of selective breeding. It is explained here, though, that the mechanisms and potentials of the two can be profoundly different. This does not mean that every GEO is ecologically dangerous; but some types of GEOs may be considerably more risky than what could be produced with selective breeding, especially when an ecologically competent host is supplemented with novel features that may increase its competitiveness. In addition, genetic ‘side effects’ raise food‐safety issues; and the possibility that they may sometimes increase ecological competitiveness cannot be ruled out, though this would be quite rare. Field plots have a proper use: to gather particular data that could be used in analysing the risks of commercial releases. But it is not scientific to call a small, confined, field population, isolated from potential competitors, a ‘test or release’ and then conclude that because ‘nothing happened’ the GEO will be safe when commercialized, or indeed that all GEOs will be safe.
Studying and managing the risk of cross‐fertilization between transgenic crops and wild relatives
Authors: KAREIVA P. , MORRIS W. , JACOBI C. M. 
Published: April 2008

AbstractDrawing on field studies of pollen dispersal, we identify features of the hybridization process that need quantification. Our emphasis is on standardized measures, as opposed to the idiosyncratic and often anecdotal methods with which gene flow or out‐crossing data are currently reported. In addition to proposing specific maximum likelihood approaches, we summarize some results to date from small‐scale field trials that bear on the risks anticipated for large‐scale commercialization. We conclude that absolute containment of recombinant pollen or genes is unlikely if physical isolation is the only containment strategy. Because we conclude that the escape of transgenic pollen is inevitable, we argue that the focus of risk analysis should be shifted towards the ‘invasiveness’ of transgenic plants and ‘mitigation’ of their impact on natural, as well as agricultural systems.
The impact of hybrids between genetically modified crop plants and their related species: introgression and weediness
Authors: DARMENCY H. 
Published: April 2008

AbstractAssessing the impact of hybrids between transgenic plants and nontarget wild species involves answering several questions such as: (i) what are the hybridization and introgression rates; (ii) what is the behaviour of a transgene in a wild population; and (iii) what will be the consequences of the expression of a transgene in a wild population? These issues are discussed using results from experiments on oilseed rape and wild related Brassiceae. Evidence is given of large variations in the estimates of cross‐fertilization probabilities. The first stage of introgression into wild populations is demonstrated to occur spontaneously through back‐crossing. Population analysis may also be valuable to detect traces of past introgression. Data from the literature on weed biology, and especially herbicide resistance, are used to illustrate the behaviour of a new gene in weed populations. The need for computer models simulating the introgression process is stressed.
The impact of hybrids between genetically modified crop plants and their related species: biological models and theoretical perspectives
Authors: GLIDDON C. 
Published: April 2008

SummaryForces affecting the rate of spread and increase of hybrids between genetically modified crop plants and their related species remain qualitatively similar, irrespective of whether genetic modification was achieved using traditional methods, those of biotechnology or as a result of the natural evolutionary process. However, the precise magnitude of the forces and, consequently, the likely environmental impact of such hybrids, may depend strongly on the nature of the gene or genes introduced into the native species. While many classes of transgenes are similar to those manipulated by conventional breeding techniques or evolution, biotechnology offers the potential to introduce genes into crops which are novel both from the point of view of function and origin. The qualitative similarity between transgenes and the products of conventional or evolutionary modification suggests that a historical view of the environmental impact of hybrids between traditionally produced crops or exotic species and their relatives would be of use in estimating the probable fate of hybrids containing transgenes in the environment. However, with certain classes of transgenes for which there are no existing analogues, there will need to be greater care in assessing the possible risks associated with release into the environment.
Differentiation of aphid clones by arbitrarily primed polymerase chain reaction (AP‐PCR) DNA fingerprinting
Authors: FUKATSU T. , ISHIKAWA H. 
Published: April 2008

AbstractDifferentiation of aphid clones was attempted using AP‐PCR which is a simple and rapid method to obtain DNA fingerprints of complex genomes. To establish optimal reaction conditions and examine reproducibility of the method, a laboratory‐maintained clone of the pea aphid, Acyrthosiphon pisum, was used as test material. Under the reaction conditions employed, identical fingerprint patterns were obtained throughout a wide range of template DNA amount, from 5 to 800 ng, and irrespective of aphid instar. No changes in the patterns were seen throughout five parthenogenetic generations. When this method was applied to a wild population of the gall‐forming aphid, Ceratovacuna nekoashi, five groups of insects originating from different galls formed on the same twig were successfully differentiated from one another by means of polymorphic fingerprint bands. In contrast, the fingerprints of the insects derived from the subgalls of the same gall were identical. These results indicated that in C. nekoashi: (i) members of a gall constitute a clonal population; (ii) a gall is founded by a single fundatrix; and (iii) intergall migration is absent or at least not frequent.
Population genetic structure of Yushania niitakayamensis (Bambusoideae, Poaceae) in Taiwan
Authors: HSIAO J.‐Y. , RIESEBERG L. H. 
Published: April 2008

Abstract Yushania niitakayamensis is distributed in Taiwan, south‐west China and northern Philippines. In Taiwan, the species occurs in the central mountain ranges from 1500 to 3500 m in altitude. Morphological variation, especially in terms of plant height, is large, with plants ranging from 10 cm to 5 m in height. The species appears to spread mainly by rhizomes and flowers rarely, leading to the prediction that most populations are comprised of a single or a few clonal genotypes and that the observed morphological variation is primarily due to phenotypic plasticity. The purpose of the present study was to investigate the genetic structure of this species on Mt Hohuan in central Taiwan. Ten plants from a single clone and ten plants of unknown genetic background were surveyed at one site in order to select RAPD primers useful for clone identification. Plants at a second site were collected at 1‐m intervals across a 50‐m transect through the population. Plants at one extreme (exposed portion) of the transect were approximately 15–30 cm in height, whereas plants up to 410 cm in height were found at the other shaded end of the transect. Comparison of amplification profiles for 12 primers revealed that in contrast to our predictions of genetic uniformity, many samples had reproducibly different RAPD amplification profiles, with the 51 samples representing 31 clones. These data imply that the clone size is relatively small, and the population is actually highly diverse genetically. The genetic variation in this population may be due to a higher frequency of sexual reproduction during the evolutionary history of the species and/or a high somatic mutation rate for RAPD loci in clones of Yushania.
A molecular analysis of relationships and biogeography within a species complex of Holarctic fish (genus Osmerus)
Authors: TAYLOR E. B. , DODSON J. J. 
Published: April 2008

AbstractEpisodes of trans‐Arctic faunal exchange and isolation between the north Pacific and Atlantic ocean basins have been implicated as important historic geological events contributing to extant patterns of genetic diversity and structure in Holarctic faunas. We made a further test of the significance of such biogeographic events by examining mitochondrial DNA (mtDNA) restriction fragment length and cytochrome b sequence polymorphism among north Pacific and Arctic, north‐western Atlantic (north‐eastern North American), and north‐eastern Atlantic (European) regional forms of the boreal smelt, genus Osmerus. Our analyses also assessed whether the regional forms within this ‘species complex’: (i) represent a single widely distributed and polytypic species, or is composed of three geographically distinct species, and (ii) resulted from a single split from north Pacific ancestral Osmerus or two independent Pacific‐Atlantic divergences. MtDNA sequence divergence estimates among forms ranged from 5.6–8.9% and from 6.1–8.5% based on restriction fragment and 300 base pairs of cytochrome b sequencing, respectively. Divergence within forms averaged less than 0.5% for fragment analysis and no differences were detected from sequence analysis. Provisional dating of lineage separations in Osmerus based on our sequence divergence estimates suggested a mid‐Pliocene to early Pleistocene time frame for diversification among the forms. These estimated lineage separation dates support the idea that geological events in ‘Beringia’ and the surrounding trans‐Arctic area (e.g. opening of the Bering Seaway, Pleistocene glacial advances), occurring over a similar time frame, have influenced radiation in Osmerus. Phenetic and parsimony analyses of the sequence divergence estimates and of sequence polymorphisms suggested that the north Pacific/Arctic form and the northwestern Atlantic form shared a common ancestor more recently than either has with the north‐eastern Atlantic form, thus supporting the hypothesis that the species complex has arisen from two independent Pacific‐Atlantic divergences probably beginning during the mid‐Pliocene.
Differential expression of genes of Pseudomonas syringae on leaves and in culture evaluated with random genomic lux fusions
Authors: CIRVILLERI G. , LINDOW S. E. 
Published: April 2008

AbstractDifferential expression of genes of Pseudomonas syringae strain B728a on plants and in culture was assessed by measuring light production by a large collection of mutant strains containing random genomic insertions of a promoterless lux operon. Reporter gene fusions were made using Tn4431 containing luxCDABE from Vibrio fisheri. Light production reproducibly increased seven‐fold when n‐decanal was added to cells harvested from plant surfaces, to over 800‐fold when added to cells cultured on a solidified culture medium, thus increasing the sensitivity of this reporter gene system. One of the 173 mutants tested exhibited significantly higher light production on plants than on solidified culture media compared to other mutants, while one lux fusion‐containing strain produced significantly more light on culture media than on plants relative to the other mutants. The plant‐inducible genes identified were not required for pathogenicity of this strain. Approximately 2% of the genes of P. syringae are apparently transcribed more actively in cells growing epiphytically on plants than in common culture media indicating that bacterial cells on plants may have substantially different behaviours than that of cultured cells.
Mate fidelity and parentage in Cory's shearwater Calonectris diomedea ‐ field studies and DNA fingerprinting
Authors: SWATSCHEK I. , RISTOW D. , WINK M. 
Published: April 2008

AbstractField studies on Cory's shearwater Calonectris diomedea, which were carried out in a breeding colony in the Aegean Sea between 1989 and 1993, revealed that almost all breeding mates stay together over many consecutive years. Mates usually changed when one partner disappeared (e.g. through death), whereas ‘divorce’ occurred at a rate of 2.7%. Since birds are nesting at very close quarters, the potential for extrapair copulation (EPC) and subsequent extrapair fertilization (EPF) seems to be high. Multilocus DNA fingerprints were used to determine the true parentage of 46 offspring (broods contain a single chick only) from 29 pairs (few pairs were studied in two and three successive years). There were no cases of extrapair paternity.
Multilocus DNA fingerprinting detects population differentiation in the outbred and abundant fish species Poecilia latipinna
Authors: LAUGHLIN T. F. , TURNER B. J. 
Published: April 2008

AbstractSeveral workers have suggested that multilocus multilocus variable number of tandem repeat (VNTR) based ‘DNA fingerprints’ are not useful in detecting differentiation among outbred populations. They suggest that the extremely high mutation rates and complexity associated with multilocus VNTR fragments make detection of interpopulation differences against a background of extremely high intrapopulation variation unlikely. This paper shows that DNA fingerprinting with the multilocus VNTR probes (GACA)4 and (CT)9 reveal significant population differences in VNTR frequencies between Florida and Georgia populations of the outbred, abundant and vagile fish species Poecilia latipinna. Differences in mutation rates among some VNTR loci may account for the ability to detect interpopulation differentiation with these probes. These results suggest that appropriate species/probe combinations would allow investigations of population structure on a microgeographical scale even in outbred species with multilocus VNTR probes where less‐sensitive techniques have failed.
Genetic variation of microsatellite loci in a bottlenecked species: the northern hairy‐nosed wombat Lasiorhinus krefftii
Authors: TAYLOR A. C. , SHERWIN W. B. , WAYNE R. K. 
Published: April 2008

AbstractWe investigate the utility of hypervariable microsatellite loci to measure genetic variability remaining in the northern hairy‐nosed wombat, one of Australia's rarest mammals. This species suffered a dramatic range and population reduction over the past 120 years and now exists as a single colony of about 70 individuals at Epping Forest National Park, central Queensland. Because our preliminary research on mitochondrial DNA and multilocus DNA fingerprints did not reveal informative variation in this population, we chose to examine variation in microsatellite repeats, a class of loci known to be highly polymorphic in mammals. To assess the suitability of various wombat populations as a reference for comparisons of genetic variability and subdivision we further analysed mitochondrial DNA cytochrome b sequence, using phylogenetic methods. Our results show that appreciable levels of variation still exist in the Epping Forest colony although it has only 41% of the heterozygosity shown in a population of a closely‐related species. From museum specimens collected in 1884, we also assessed microsatellite variation in an extinct population of the northern hairy‐nosed wombat, from Deniliquin, New South Wales, 2000 km to the south of the extant population. The apparent loss of variation in the Epping Forest colony is consistent with an extremely small effective population size throughout its 120‐year decline.