bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biting behaviour and potential vector status of anthropophilic blackflies in a new focus of human onchocerciasis at Minaçu, central Brazil
Authors: Shelley A. J. , Maia‐Herzog M. , Dias A. P. A. Luna , Camargo M. , Costa E. G. , Garritano P. , Lowry C. A. 
Published: March 2003

SummaryMonthly collections were made of man‐biting female blackflies: Simulium auripellitum Enderlein, S. guianense Wise, S. minusculum Lutz and S. nigrimanum Macquart (Diptera: Simuliidae) from four catching stations in the newly discovered focus of human onchocerciasis at Minaçu (13°35′ S 48°18′ W), 300 km north of Brasília in Goiás State. These provided baseline data on biting habits, population density and seasonal prevalence during the year before completion of the Serra da Mesa hydroelectric dam on the Rio Tocantins near Minaçu, in a project investigating the effect of dam construction on onchocerciasis transmission in the area. All four simuliid species were most abundant during the dry season, and only bit in low numbers (S. auripellitum S.minusculum, S. nigrimanum) or were absent (S. guianense) in the wet season. Simulium minusculum was the predominant species at all catching stations, being particularly abundant by the large River Tocantins. The other three species were mainly associated with smaller rivers. In the dry season, biting rhythms of S. minusculum varied with catching site, while S. nigrimanum showed peaks of activity in early morning and during the afternoon. Experimental infection with Onchocerca volvulus (Leuckart) (Nematoda: Onchocercidae), from a human volunteer, showed that this parasite could develop fully in the four simuliid species, which are all considered to be potential vectors in the area.
Estimating population structure in diploids with multilocus dominant DNA markers
Authors: Zhivotovsky Lev A. 
Published: March 2003

AbstractMultilocus DNA markers [random amplified polymorphic DNA (RAPDs), amplified fragment length polymorphism (AFLPs)] are important for population studies because they reveal many polymorphic loci distributed over the genome. The markers are dominant, that is two phenotypes are distinguished at each locus, with a band and with no band. The latter one represents null‐homozygotes with unamplified, recessive null‐alleles. The frequency of a null‐allele can be estimated by taking the square root of the fraction of individuals with no band. Lynch and Milligan (1994) have suggested a modified procedure that reduces bias introduced by the square‐root transform. However, the procedure recommends to ignore those samples in which fewer than four null‐homozygotes are observed. This may lead to significant bias in estimates of genetic diversity. In this study, I introduce a Bayesian approach to estimation of null‐allele frequencies for dominant DNA markers. It follows from computer simulations and data on two conifer species that the Bayesian method gives nearly unbiased estimates of heterozygosity, genetic distances andF‐statistics. The influence of a prior distribution and departure from Hardy–Weinberg proportions on the estimates is also considered.
Ribosomal small subunit sequence variation within spores of an arbuscular mycorrhizal fungus, Scutellospora sp.
Authors: Clapp J. P. , Fitter A. H. , Young J. P. W. 
Published: March 2003

AbstractRoots of bluebell (Hyacinthoides nonscripta) were sampled from a woodland in Yorkshire, UK and spores of an arbuscular mycorrhizal fungus Scutellospora sp., were obtained from the surrounding soil. Partial small subunit (SSU) ribosomal RNA sequences were amplified from both roots and spores using either the universal forward primer SS38 or the Glomales‐specific primer VANS1, with the reverse Gigasporaceae‐specific primer VAGIGA. Amplified products were cloned and sequenced. Both spores and roots yielded sequences related to those known from fungi within the Glomales, with up to four distinct SSU sequences obtained from individual spores. The VANS1 primer‐binding site varied considerably in sequence and only a subset of Scutellospora sequences were amplified when the VANS1 primer was used. In addition to glomalean sequences, a number of different sequences, apparently from ascomycetes, were obtained from both root and spore samples.
Extent and degree of hybridization between exotic (Spartina alterniflora) and native (S. foliosa) cordgrass (Poaceae) in California, USA determined by random amplified polymorphic DNA (RAPDs)
Authors: Ayres Debra R. , Garcia‐Rossi Dino , Davis Heather G. , Strong Donald R. 
Published: March 2003

Abstract Spartina alterniflora, smooth cordgrass, native to the eastern USA, was introduced into south San Francisco Bay ≈ 25 years ago. It has spread by purposeful introduction of rooted plants and dispersal of seeds on the tides. Previous work suggested that S. alterniflora was competitively superior to the native California cordgrass, S. foliosa, and that the two species hybridized. The present study determined the spread of S. alterniflora and S. foliosa × alterniflora hybrids in California and examined the degree of hybridization. We used nuclear DNA markers diagnostic for each species to detect the parental species and nine categories of hybrids. The California coast outside San Francisco Bay contained only the native species. All hybrid categories exist in the Bay, implying that several generations of crossing have occurred and that hybridization is bidirectional. Hybrids were found principally near sites of deliberate introduction of the exotic species. Where S. alterniflora was deliberately planted, we found approximately equal numbers of S. alterniflora and hybrid individuals; S. foliosa was virtually absent. Marshes colonized by water‐dispersed seed contained the full gamut of phenotypes with intermediate‐type hybrids predominating. The proliferation of hybrids could result in local extinction of S. foliosa. What is more, S. alterniflora has the ability to greatly modify the estuary ecosystem to the detriment of other native species and human uses of the Bay. To the extent that they share these engineering abilities, the proliferation of cordgrass hybrids could grossly alter the character of the San Francisco Bay.
Genetic structure and gene flow among Komodo dragon populations inferredby microsatellite loci analysis
Authors: Ciofi Claudio , Bruford Mike W. 
Published: March 2003

AbstractA general concern for the conservation of endangered species is the maintenance of genetic variation within populations, particularly when they become isolated and reduced in size. Estimates of gene flow and effective population size are therefore important for any conservation initiative directed to the long‐term persistence of a species in its natural habitat. In the present study, 10 microsatellite loci were used to assess the level of genetic variability among populations of the Komodo dragonVaranus komodoensis. Effective population size was calculated and gene flow estimates were compared with palaeogeographic data in order to assess the degree of vulnerability of four island populations. Rinca and Flores, currently separated by an isthmus of about 200 m, retained a high level of genetic diversity and showed a high degree of genetic similarity, with gene flow values close to one migrant per generation. The island of Komodo showed by far the highest levels of genetic divergence, and its allelic distinctiveness was considered of great importance in the maintenance of genetic variability within the species. A lack of distinct alleles and low levels of gene flow and genetic variability were found for the small population of Gili Motang island, which was identified as vulnerable to stochastic threats. Our results are potentially important for both the short‐ and long‐term management of the Komodo dragon, and are critical in view of future re‐introduction or augmentation in areas where the species is now extinct or depleted.
Armadillos exhibit less genetic polymorphism in North America than in South America: nuclear and mitochondrial data confirm a founder effect in Dasypus novemcinctus (Xenarthra)
Authors: Huchon Dorothée , Delsuc Frédéric , Catzeflis François M. , Douzery Emmanuel J. P. 
Published: March 2003

AbstractHeterozygosity at eight nuclear enzymatic loci and mitochondrial DNA control region (D‐loop) sequence polymorphism was compared between North and South American nine‐banded armadillos (Dasypus novemcinctus: Xenarthra, Dasypodidae). All markers revealed a striking genetic homogeneity amongst Texas, Louisiana, and Mississippi individuals, vs. the usual level of polymorphism for the French Guiana population. This may reflect a founder effect during colonization of North America. Occurrence of polymorphism in the D‐loop microsatellite motif of North American armadillos suggests a recent recovery of mitochondrial variability. Phylogeographic analyses using Dasypus kappleri as outgroup provides evidence for a clear separation between North and South American control region haplotypes.
Mating frequency and genetic structure of the Argentine antLinepithema humile
Authors: Krieger Michael J. B. , Keller Laurent 
Published: March 2003

AbstractThe nest and population genetic structures of the Argentine ant,Linepithema humilewere investigated using eight microsatellite loci. Genotypes of the sperm from spermathecae of 87 queens were consistent with all queens being singly inseminated. The probability of a double mating remaining undetected was low (0.012) suggesting that no queens or only a very low proportion mate multiply. The relatedness between the queens and their mates was negative (R = −0.164 ± 0.044) and significantly different to zero (P = 0.020). However, the high negative relatedness value was caused by a significant allele frequency difference between the sexes at a single locus (Lhum‐28). When this locus was removed from the analyses, the relatedness was not significantly different from zero (R = 0.013 ± 0.050,P = 0.812). Analysis of 10 nests revealed that the genetic differentiation among nests was weak (FST = 0.003) and not distinguishable from zero (P = 0.468). Similarly, the overall relatedness among nestmate females was not significantly different from zero (R = 0.007 ± 0.018,P = 0.706). These results are consistent with the lack of distinct nest boundaries and the large number of queens per nest in the population studied. Although mating takes place inside the nest, the inbreeding coefficient was close to zero (F = 0.007 ± 0.025,P = 0.786). Overall, these data indicate substantial local gene flow mediated by movement of reproductives among colonies.
Conservation genetics of bush mango from central/west Africa: implications from random amplified polymorphic DNA analysis
Authors: Lowe A. J. , Gillies A. C. M. , Wilson J. , Dawson I. K. 
Published: March 2003

AbstractGenetic variation was assessed in the two bush mango species, Irvingia gabonensis and I. wombolu, valuable multipurpose fruit trees from central and west Africa that are currently undergoing domestication. A total of 130 individuals sampled from Cameroon, Nigeria and Gabon were analysed using 74 random amplified polymorphic DNAs (RAPDs). Significant genetic integrity was found in the two morphologically similar species (among‐species analysis of molecular variance [amova] variance component 25.8%, P < 0.001), with no evidence of hybridization, even between individuals from areas of sympatry where hybridization was considered probable. Results suggest that large‐scale transplantation of either species into new habitats will probably not lead to genetic introgression from or into the other species. Therefore, subsequent cultivation of the two species should not be hindered by this consideration, although further studies on the potential for hybridization/introgression between these species would be prudent. Significant genetic differentiation of both species (among‐countries within species, nested amova variance component 9.8%, P < 0.001) was observed over the sampled regions, and genetic similarity of samples decreased significantly with increasing geographical distance, according to number of alleles in common (NAC) analysis. ‘Hot spots’ of genetic diversity were found clustered in southern Nigeria and southern Cameroon for I. wombolu, and in southern Nigeria, southern Cameroon and central Gabon for I. gabonensis. The possible reasons for this distribution of genetic variation are discussed, but it may reflect evolutionary history, as these populations occur in areas of postulated Pleistocene refugia. The application of these results to domestication programmes and, in the light of extensive deforestation in the region, conservation approaches, is discussed.
Effect of crop rotation and soil cover on alteration of the soil microflora generated by the culture of transgenic plants producing opines
Authors: Oger P. , Mansouri H. , Dessaux Y. 
Published: March 2003

AbstractThe culture of transgenic Lotus corniculatus plants producing opines, which are bacterial growth substrates, leads to the selection of rhizospheric bacteria able to utilize these substrates. We have investigated the fate of the opine‐utilizing community over time under different experimental conditions following elimination of selective pressure exerted by the transgenic plants. These plants were removed from the soil, which was either left unplanted or replanted with wild‐type L. corniculatus or wheat plants. The density of opine‐utilizing bacteria in the fallow soils remained essentially unchanged throughout the experiment, regardless of the soil of origin (soil planted with wild‐type or transgenic plants). When wild‐type Lotus plants were used to replace their transgenic counterparts, only the bacterial populations able to utilize the opines were affected. Long‐term changes affecting the opine‐utilizing bacterial community on Lotus roots was dependent upon the opine studied. The concentration of nopaline utilizers decreased, upon replacement of the transgenic plants, to a level similar to that of normal plants, while the concentration of mannopine utilizers decreased to levels intermediate between transgenic and normal plants. These data indicate that: (i) the opine‐utilizing bacterial populations can be controlled in the rhizosphere via plant‐exudate engineering; (ii) the interaction between the engineered plants and their root‐associated micro‐organisms is transgene specific; and (iii) alterations induced by the cultivation of transgenic plants may sometimes be persistent. Furthermore, opine‐utilizing bacterial populations can be controlled by crop rotation. Therefore, favouring the growth of a rhizobacterium of agronomic interest via an opine‐based strategy appears feasible.
Mitochondrial haplotype variation and phylogeography of Iberian brown trout populations
Authors: Machordom A. , Suárez J. , Almodóvar A. , Bautista J. M. 
Published: March 2003

AbstractThe biogeographical distribution of brown trout mitochondrial DNA haplotypes throughout the Iberian Peninsula was established by polymerase chain reaction‐restriction fragment polymorphism analysis. The study of 507 specimens from 58 localities representing eight widely separated Atlantic‐slope (north and west Iberian coasts) and six Mediterranean drainage systems served to identify five main groups of mitochondrial haplotypes: (i) haplotypes corresponding to non‐native, hatchery‐reared brown trout that were widely distributed but also found in wild populations of northern Spain (Cantabrian slope); (ii) a widespread Atlantic haplotype group; (iii) a haplotype restricted to the Duero Basin; (iv) a haplotype shown by southern Iberian populations; and (v) a Mediterranean haplotype. The Iberian distribution of these haplotypes reflects both the current fishery management policy of introducing non‐native brown trout, and Messinian palaeobiogeography. Our findings complement and extend previous allozyme studies on Iberian brown trout and improve present knowledge of glacial refugia and postglacial movement of brown trout lineages.
Reconciling patterns of genetic variation with stream structure, earth history and biology in the Australian freshwater fish Craterocephalus stercusmuscarum (Atherinidae)
Authors: Mcglashan D. J. , Hughes J. M. 
Published: March 2003

AbstractWe examined the consequences of barriers, stream architecture and putative dispersal capability on levels of genetic differentiation among populations of the freshwater fish Craterocephalus stercusmuscarum. Seven polymorphic allozyme loci and sequences of a 498‐bp fragment of the ATPase 6 mitochondrial DNA (mtDNA) gene were used to assess patterns of genetic variation among 16 populations from upland and lowland streams of five drainages in northern Queensland, Australia. Concordant patterns at both genetic markers revealed that there were significant levels of genetic subdivision among all populations, while an analysis of molecular variation showed that the distribution of genetic diversity was not consistent with contemporary drainage structure. There were reciprocally monophyletic mtDNA clades and fixed or large frequency differences at allozyme loci either side of instream barriers such as waterfalls. This implied barriers were effective in restricting gene flow between upland and lowland populations separated by waterfalls. However, there were two genetically distinct groups in upland areas, even within the same subcatchment, as well as high levels of genetic subdivision among lowland populations, suggesting barriers alone do not explain the patterns of genetic diversity. The data revealed a complex phylogeographic pattern, which we interpreted to be the result of one or more invasion events of independent lineages to different sections of each drainage, possibly mediated by well documented geomorphological changes. Our results highlight the importance of earth structure and history in shaping population genetic structure in stream organisms where dispersal capability may be limited, and reveal that the contemporary structure of drainages is not necessarily a good indicator of genetic relationships among populations.
Complex mutations in a high proportion of microsatellite loci from the protozoan parasite Plasmodium falciparum
Authors: Anderson Timothy J. C. , Su Xin‐Zhuan , Roddam AndreW. , Day Karen P. 
Published: March 2003

AbstractMicrosatellite loci are generally assumed to evolve via a stepwise mutational process and a battery of statistical techniques has been developed in recent years based on this or related mutation models. It is therefore important to investigate the appropriateness of these models in a wide variety of taxa. We used two approaches to examine mutation patterns in the malaria parasite Plasmodium falciparum: (i) we examined sequence variation at 12 tri‐nucleotide repeat loci; and (ii) we analysed patterns of repeat structure and heterozygosity at 114 loci using data from 12 laboratory parasite lines. The sequencing study revealed complex patterns of mutation in five of the 12 loci studied. Alleles at two loci contain indels of 24 bp and 57 bp in flanking regions, while in the other three loci, blocks of imperfect microsatellites appear to be duplicated or inserted; these loci essentially consist of minisatellite repeats, with each repeat unit containing four to eight microsatellites. The survey of heterozygosity revealed a positive relationship between repeat number and microsatellite variability for both di‐ and trinucleotides, indicating a higher mutation rate in loci with longer repeat arrays. Comparisons of levels of variation in different repeat types indicate that the mutation rate of dinucleotide‐bearing loci is 1.6–2.1 times faster than trinucleotides, consistent with the lower mean number of repeats in trinucleotide‐bearing loci. However, despite the evidence that microsatellite arrays themselves are evolving in a manner consistent with stepwise mutation model in P. falciparum, the high frequency of complex mutations precludes the use of analytical tools based on this mutation model for many microsatellite‐bearing loci in this protozoan. The results call into question the generality of models based on stepwise mutation for analysing microsatellite data, but also demonstrate the ease with which loci that violate model assumptions can be detected using minimal sequencing effort.
World‐wide genetic differentiation of Eubalaena: questioning the number of right whale species
Authors: Rosenbaum H. C. , Brownell R. L. , Brown M. W. , Schaeff C. , Portway V. , White B. N. , Malik S. , Pastene L. A. , Patenaude N. J. , Baker C. S. , Goto M. , Best P. B. , Clapham P. J. , Hamilton P. , Moore M. , Payne R. , Rowntree V. , Tynan C. T. , Bannister J. L. , Desalle R. 
Published: March 2003

AbstractFew studies have examined systematic relationships of right whales (Eubalaena spp.) since the original species descriptions, even though they are one of the most endangered large whales. Little morphological evidence exists to support the current species designations for Eubalaena glacialis in the northern hemisphere and E. australis in the southern hemisphere. Differences in migratory behaviour or antitropical distribution between right whales in each hemisphere are considered a barrier to gene flow and maintain the current species distinctions and geographical populations. However, these distinctions between populations have remained controversial and no study has included an analysis of all right whales from the three major ocean basins. To address issues of genetic differentiation and relationships among right whales, we have compiled a database of mitochondrial DNA control region sequences from right whales representing populations in all three ocean basins that consist of: western North Atlantic E. glacialis, multiple geographically distributed populations of E. australis and the first molecular analysis of historical and recent samples of E. glacialis from the western and eastern North Pacific Ocean. Diagnostic characters, as well as phylogenetic and phylogeographic analyses, support the possibility that three distinct maternal lineages exist in right whales, with North Pacific E. glacialis being more closely related to E. australis than to North Atlantic E. glacialis. Our genetic results provide unequivocal character support for the two usually recognized species and a third distinct genetic lineage in the North Pacific under the Phylogenetic Species Concept, as well as levels of genetic diversity among right whales world‐wide.
Markers derived from amplified fragment length polymorphism gels for plant ecology and evolution studies
Authors: Mclenachan P. A. , Stöckler K. , Winkworth R. C. , Mcbreen K. , Zauner S. , Lockhart P. J. 
Published: March 2003

AbstractWe describe the types of polymerase chain reaction (PCR) markers that we have isolated using amplified fragment length polymorphisms (AFLP) in closely related taxa from diverse plant genera. With these markers, both inter‐ and intraspecific differences have been identified. The characterization of the nucleotide sequences and fragment length polymorphisms of such AFLP‐derived PCR markers is promising for investigating the ecology and evolution of closely related plant taxa.
Patterns of genetic variation inGymnadenia conopsea, the fragrant orchid
Authors: Gustafsson S. 
Published: March 2003

AbstractGymnadenia conopsea (L.) R. Br., or the fragrant orchid, is one of many plant species negatively influenced by new practices in agriculture and forestry during the last decades. This study describes the level of microsatellite variation within and among 10 Swedish populations of this species. It was not possible to detect strong effects of small population size or fragmentation. In general, the species had high genetic variation within and low genetic divergence among populations, although the correlation between population size and number of alleles was close to significance at the 95% level. Also, a significant isolation by distance effect was observed, indicating the presence of modest restrictions in gene dispersal between the investigated populations.