bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of problem‐based learning on the academic performance of students studying podiatric medicine in Ontario
Authors: Finch  
Published: March 2003

ObjectivesTo investigate the effect of problem‐based learning (PBL) on student achievement.DesignTwo cohorts of students studying podiatric medicine in Ontario were compared – one having undertaken the traditional lecture‐based curriculum, and the other the problem‐based learning programme.SettingThe Michener Institute for Applied Health Sciences and The Toronto Hospital.SubjectsChiropody students.ResultsThe performance of the students on the written Provincial Registration Examinations of Ontario was analysed utilizing independent t‐tests and demonstrated that the PBL cohort of students achieved significantly higher overall examination scores (P < 0·005) than the traditional cohort. Further analysis revealed that no significant difference existed between student cohorts with respect to factual biomedical knowledge (P > 0·5), but that the PBL students performed significantly better in tests of deeper understanding and the cognitive skills related to patient management (P < 0·0005). Additionally, intragroup analysis using Spearman’s rank order correlation indicated that there was no rank ordered association between performance on the multiple‐choice and essay sections of the examination.ConclusionsThe above results suggest that the PBL cohort of students was more knowledgeable than, and possessed superior cognitively related patient management skills, to their traditional counterparts.
Junior doctors' views about careers in academic medicine
Authors: Goldacre Michael , Stear Sarah , Richards Rex , Sidebottom Eric 
Published: March 2003

ObjectiveTo investigate junior doctors' views about careers in academic medicine.DesignPostal questionnaire survey.SettingNational Health Service in England.SubjectsDoctors in university posts at specialist registrar level, Medical Research Council and Wellcome Trust training fellows, and specialist registrars in National Health Service posts.ResultsIncentives to pursue an academic career which respondents rated as strong related to the challenge of research and the intellectual environment of research units. The strongest disincentives were perceived difficulties in obtaining research grants and uncertainty regarding pay parity with National Health Service colleagues. Medical Research Council and Wellcome fellows had much more protected research time than other academic doctors but were less satisfied with their clinical training. Academic doctors who were not fellows reported spending less than half their time on research and the great majority agreed that their research suffers when there is pressure on the service side.ConclusionsThe job content of academic posts should be kept under regular review to ensure that clinical service pressures do not inappropriately erode research time while also ensuring that postholders have adequate clinical training. Training programmes need flexibility to accommodate the needs of clinical academics in their progress through higher specialist training.
Genetic variation inFitzroya cupressoides(alerce), a threatened South American conifer
Authors: Allnutt T. R. , Newton A. C. , Lara A. , Premoli A. , Armesto J. J. , Vergara R. , Gardner M. 
Published: March 2003

AbstractFitzroya cupressoides(alerce, Cupressaceae) is a large and exceptionally long‐lived conifer, endemic to a restricted area of southern Chile and neighbouring areas of Argentina. As a result of its high economic value, the species has been severely exploited for timber, and remnant populations are fragmented and often highly disturbed. The species is thought to have undergone a major range contraction during the last glaciation. In order to assess the extent of genetic variation using DNA markers within and between populations of this species, samples were obtained from throughout the natural range and analysed for random amplified polymorphic DNA (RAPD) variation. Eight 10‐mer and three 15‐mer primers were used to produce a total of 54 polymorphic bands. Shannon's diversity estimates were calculated to provide an estimate of the degree of variation within each population. Values varied from 0.343 to 0.636 with only the lowest value differing significantly from the others (Spop= 0.547). This indicated that there is a significant degree of variation within each population, and did not provide evidence for genetic ‘bottleneck’ effects within the species. A pairwise distance measure calculated from the RAPD data was used as an input for principal coordinate (PCO) andamovaanalyses. The first three principal coordinates of RAPD distances described 8.3, 5.9 and 5.4% of the total variance, respectively, and a degree of clustering of samples according to their geographical origin was detectable.amovaanalysis indicated that although most of the variation (85.6%) was found within populations, a significant proportion (P < 0.002) was attributable to differences between populations. Anupgmadendrogram constructed using ΦSTvalues derived fromamovaproduced a pattern broadly similar to that produced by the PCO, highlighting differences between three main groups of populations within Chile: those from the northern Coastal Range, the southern Coastal Range and Central Depression, and the Andes. Populations from Argentina also emerged as significantly different from those in Chile. These results are interpreted in the context of the postglacial history of the species, and their implications for the development of conservation strategies forFitzroyaare discussed.
Effects of natural habitat fragmentation on an endemic scrub lizard (Sceloporus woodi): an historical perspective based on a mitochondrial DNA gene genealogy
Authors: Clark A. M. , Bowen B. W. , Branch L. C. 
Published: March 2003

AbstractThe Florida scrub lizard, Sceloporus woodi, is endemic to scrub habitat patches along the central portion of the Florida peninsula and xeric coastal regions. Scrub ecosystems are the patchily distributed remnants of previously widespread habitats formed during the Pleiocene and early Pleistocene. Scrub lizards appear to have limited dispersal capabilities due to high habitat specificity and low mobility. To assess the population structure and phylogeography of S. woodi, 135 samples were collected from 16 patches on five major ridges in Florida, USA. Analysis of 273 bp of mitochondrial DNA (mtDNA) cytochrome b reveals a very strong geographic distribution of genetic diversity. Haplotype frequencies are significantly different in 63 of 66 comparisons between patches. With one exception, samples from the five major ridges are characterized by fixed differences in haplotype distribution and deep evolutionary separations (3–10%). Fixed genetic differences were also observed between northern and southern segments of several ridges. Analysis of molecular variance (amova) shows an estimated 10.4% total genetic variation within patches, 17.5% among patches (within ridges), and 72.1% among ridges. This strong population structure among patches within ridges indicates that the distribution of S. woodi is tightly linked to sandy scrub habitat and that the discontinuous distribution of scrub habitats significantly inhibits dispersal and gene flow. Phylogeographic analyses indicate a pattern of dispersal down the Florida peninsula during the late Pliocene–early Pleistocene, followed by habitat fragmentation and vicariant isolation events. Therefore, the deep genetic structuring among scrub lizard populations on separate ridges is attributed to ancient isolation events induced by a shift from dry (xeric) to wet (mesic) conditions on the Florida peninsula. These findings indicate that some scrub lizard populations have persisted in isolation for time frames in excess of 1 Myr, providing a case history on the genetic consequences of habitat fragmentation.
Cleistogamy in Scutellaria indica (Labiatae): effective mating system and population genetic structure
Authors: Sun M. 
Published: March 2003

Abstract Scutellaria indica is a perennial herb with both chasmogamous (CH) and cleistogamous (CL) flowers on the same plant in some populations, and only CL flowers in other populations. Actual seed production by CH and CL flowers was investigated in populations of S. indica. The average seed set of CL flowers was 19 times higher than CH flowers, indicating much greater fertilization success. The CL seeds were also significantly heavier than the CH seeds. However, the resource cost of producing a CH flower was much higher than that of producing a CL flower. The CH flower was approximately seven times larger, and its pollen/ovule ratio was approximately five times higher than that of CL flowers. The level and pattern of genetic diversity at both allozyme and random amplified polymorphic DNA (RAPD) levels were consistent with a predominantly selfing system in the species. The average amount of within‐population genetic variation was extremely low (A = 1.025, P = 2.36%, HO = 0.001 and HE = 0.008 based on allozyme data, and P = 8.94% and HE = 0.03 based on RAPD data). At the species level, the estimates of total gene diversity (HT) were 0.101 based on allozyme data and 0.139 based on RAPD data. A very high level of genetic differentiation occurred between populations (allozyme GST = 0.92 and RAPD GST = 0.81). Genetic drift coupled with predominant cleistogamous selfing apparently played the major role in determining the population genetic structure in S. indica. Although the features associated with CH and CL flower and seed production seem to be sufficient for the evolution of complete cleistogamy in S. indica, random fixation of alternative alleles for dimorphic or complete cleistogamy in small populations could maintain the multiple strategy of chasmogamous and cleistogamous reproduction in the species.
Genetic variation in postfire aspen seedlings in Yellowstone National Park
Authors: Stevens Michael T. , Turner Monica G. , Tuskan Gerald A. , Romme William H. , Gunter Lee E. , Waller Donald M. 
Published: March 2003

AbstractA rare episode of regeneration of aspen (Populus tremuloides Michx.) by seeds occurred in Yellowstone National Park (YNP), Wyoming, USA, following extensive fires that occurred in 1988. In 1997, we sampled 410 aspen seedlings from 23 local populations distributed widely across YNP to determine how genetic diversity varies with elevation, substrate, plant competition, ungulate browsing, and geographical location. We employed 132 randomly amplified polymorphic DNA (RAPD) markers based on six primers to show genetic relationships within and among the postfire aspen seedling populations. Measures of genetic variation, including estimates of percentage polymorphic loci, expected heterozygosity, and Nei’s FST, indicated that most of the variation occurred within rather than among local populations. There was no indication of geographical differentiation among sampled populations based on hierarchal estimates of Nei’s FST, neighbour‐joining, or correlations between genetic distance and geographical distance. Even genetically distant populations shared nearly 90% of the same markers. Within plots, the amount of genetic variation decreased slightly in response to increased percentage vegetative cover, mean seedling basal diameter, and mean seedling height. Geological substrate, density of lodgepole pine (Pinus contorta var. latifolia Dougl.) seedlings, browsing intensity, and elevation were not significantly related to levels of genetic variation within the seedling plots. These data suggest that genetic variation and geographical structure among seedling populations may occur over time as the transition from seedling‐dominated stands to clone‐dominated stands occurs.
Phylogeography and mitochondrial DNA (mtDNA) diversity in North American collared lemmings (Dicrostonyx groenlandicus)
Authors: Ehrich D. , Fedorov V. B. , Stenseth N. C. , Krebs C. J. , Kenney A. 
Published: March 2003

AbstractVariation in the nucleotide sequence of the mitochondrial control region (250 bp) and the cytochrome b region (870 bp) was examined in collared lemmings (Dicrostonyx groenlandicus) from 19 localities in northern Alaska and the Canadian Arctic. The division of D. groenlandicus in two phylogeographical groups with limited divergence across the Mackenzie River is consistent with the separation of this species in more than one refugial area located to the northwest of the Laurentide ice sheet during the last glaciation. Populations of D.groenlandicus from formerly glaciated areas are no less variable than those in nonglaciated areas. Instead, the low intrapopulation and intraregional diversity estimates in D. groenlandicus are probably a result of regional bottleneck events due to range contractions during Holocene warming events. These results are consistent with findings previously reported on collared lemmings (D. torquatus) from the Eurasian Arctic.
Comparison of microsatellites and amplified fragment length polymorphism markers for parentage analysis
Authors: Gerber S. , Mariette S. , Streiff R. , Bodénès C. , Kremer A. 
Published: March 2003

AbstractThis study compares the properties of dominant markers, such as amplified fragment length polymorphisms (AFLPs), with those of codominant multiallelic markers, such as microsatellites, in reconstructing parentage. These two types of markers were used to search for both parents of an individual without prior knowledge of their relationships, by calculating likelihood ratios based on genotypic data, including mistyping. Experimental data on 89 oak trees genotyped for six microsatellite markers and 159 polymorphic AFLP loci were used as a starting point for simulations and tests. Both sets of markers produced high exclusion probabilities, and among dominant markers those with dominant allele frequencies in the range 0.1–0.4 were more informative. Such codominant and dominant markers can be used to construct powerful statistical tests to decide whether a genotyped individual (or two individuals) can be considered as the true parent (or parent pair). Gene flow from outside the study stand (GFO), inferred from parentage analysis with microsatellites, overestimated the true GFO, whereas with AFLPs it was underestimated. As expected, dominant markers are less efficient than codominant markers for achieving this, but can still be used with good confidence, especially when loci are deliberately selected according to their allele frequencies.
Highly reliable genetic identification of individual northern hairy‐nosed wombats from single remotely collected hairs: a feasible censusing method
Authors: Sloane M. A. , Sunnucks P. , Alpers D. , Beheregaray L. B. , Taylor A. C. 
Published: March 2003

AbstractThe highly endangered northern hairy‐nosed wombat (Lasiorhinus krefftii) is extremely difficult to study in the wild, and its numbers correspondingly difficult to estimate. Disturbance to the animals caused by trapping and radio‐tracking may not only constitute an excessive risk to the population’s viability, but may also yield biased data. The results of a pilot study are presented, which clearly show noninvasive genotyping to be a highly feasible and reliable alternative censusing method forL. krefftii. The protocol can identify individual wombats from single hairs collected remotely at burrow entrances, using: (i) a panel of microsatellite markers giving individual‐specific genotypes; and (ii) a Y‐linked sexing marker in combination with a single‐copy X‐linked amplification control. Using just the eight most variable microsatellites (of 20 available), only one in 200 pairs of full‐sibs are predicted to share the same genotype. From 12 wombat hair samples collected on tape suspended over burrow entrances, three known female, two known male and an unknown wombat of each sex were identified. The approach will allow censusing of individuals that evade capture, and will also reveal some otherwise problematic aspects of the behaviour of this elusive animal.
Testing models of diversification in mice in the Abrothrix olivaceus/xanthorhinus complex in Chile and Argentina
Authors: Smith M. F. , Kelt D. A. , Patton J. L. 
Published: March 2003

AbstractSamples of the forest‐dwelling mouse Abrothrix olivaceus and the steppe‐dwelling A. xanthorhinus across a transect between 45 and 47° S in southern Chile were analysed using the mitochondrial cytochrome b (cyt b) sequence, substantially adding to the data presented previously for these taxa from Argentina and Chile. The level of variation in the cyt b sequence throughout the entire olivaceus/xanthorhinus complex is comparable to that seen within a single species in many South American sigmodontine rodents, consistent with a previous conclusion that both taxa are sub‐species of A. olivaceus. Haplotypes of xanthorhinus have not yet achieved reciprocal monophyly relative to those of olivaceus. We evaluate competing hypotheses for the morphological divergence of xanthorhinus and olivaceus by allopatry in Pleistocene refuges versus postglacial diversification across ecological gradients. Two contrasting patterns are predicted for plots of the distribution of pairwise genetic differences, depending on whether the taxa diverged in allopatric refuges or through selection across a gradient. Examples of both modes of diversification are found in this complex.
Phylogeography and conservation of impala and greater kudu
Authors: Nersting Louise Grau , Arctander Peter 
Published: March 2003

AbstractThe phylogeography of the bush habituated African bovid species impala (Aepyceros melampus) and greater kudu (Tragelaphus strepsiceros) is investigated using mitochondrial DNA (mtDNA) markers. Combined analysis of individual lineages, relationships and population genetics suggest a colonization process from Southern Africa toward Eastern regions in the greater kudu. Results are less clear for the impala, although remaining consistent with a similar pattern of historical dispersion. The study reveals a similar pattern, that is a marked divergence of lineages from South‐western Africa relative to other regions. This pattern is opposed to previously published findings in other African bovid species. In the impala, the genetically isolated region is consistent with morphology because it is recognized as the subspecies A. m. petersi, the black‐faced impala. In contrast, the similar split of South‐western mitochondrial lineages was not expected in the greater kudu on the basis of morphology. Both species show a significant population genetic differentiation. Beyond their phylogeographical value, our results should raise conservation concerns about South‐western populations of both species. The black‐faced impala is categorized as vulnerable and our data show indications of hybridization with common impala A. m. melampus. The previously unrecognized genetic status of the South‐western kudus could also imply conservation regulations.
Immunological analysis of phloem sap of Bacillus thuringiensis corn and of the nontarget herbivore Rhopalosiphum padi (Homoptera: Aphididae) for the presence of Cry1Ab
Authors: Raps A. , Kehr J. , Gugerli P. , Moar W. J. , Bigler F. , Hilbeck A. 
Published: March 2003

AbstractPhloem sap of transgenic Bacillus thuringiensis (Bt) corn expressing a truncated form of the B. thuringiensisδ‐endotoxin Cry1Ab, sap sucking aphids feeding on Bt corn and their honeydew were analysed for presence of Cry1Ab using ELISA. Phloem sap of Bt and non‐Bt corn was collected using a newly developed technique with a microcapillary being directly inserted into the phloem tubes. Using this technique, no Cry1Ab was detected in the phloem sap. In contrast, measurable concentrations of Cry1Ab in the range of 1 ppb were detected when phloem sap of pooled leaf samples was extracted using EDTA buffer. This was probably because of Cry1Ab toxin released from damaged cells. When analysing apterous adults of Rhopalosiphum padi L. and their honeydew, no Cry1Ab could be detected. In contrast, Cry1Ab was clearly detected in both larvae of the leaf chewing herbivore Spodoptera littoralis (Boisduval) and their faeces, showing that Cry1Ab is detectable after ingestion and excretion by herbivores. These results suggest that R. padi ingests or contains no or only very low concentrations of Cry1Ab in the range of the detection limit. In consequence it is hypothesized that R. padi as an important prey for beneficial insects in corn is unlikely to cause any harm to its antagonists due to mediating Bt toxin.
Speciation in rapidly diverging systems: lessons from Lake Malawi
Authors: Danley Patrick D. , Kocher Thomas D. 
Published: March 2003

AbstractRapid evolutionary radiations provide insight into the fundamental processes involved in species formation. Here we examine the diversification of one such group, the cichlid fishes of Lake Malawi, which have radiated from a single ancestor into more than 400 species over the past 700 000 years. The phylogenetic history of this group suggests: (i) that their divergence has proceeded in three major bursts of cladogenesis; and (ii) that different selective forces have dominated each cladogenic event. The first episode resulted in the divergence of two major lineages, the sand‐ and rock‐dwellers, each adapted to a major benthic macrohabitat. Among the rock‐dwellers, competition for trophic resources then drove a second burst of cladogenesis, which resulted in the differentiation of trophic morphology. The third episode of cladogenesis is associated with differentiation of male nuptial colouration, most likely in response to divergent sexual selection. We discuss models of speciation in relation to this observed pattern. We advocate a model, divergence with gene flow, which reconciles the disparate selective forces responsible for the diversification of this group and suggest that the nonadaptive nature of the tertiary episode has significantly contributed to the extraordinary species richness of this group.
Chloroplast microsatellites and mitochondrial nad1 intron 2 sequences indicate congruent phylogenetic relationships among Swiss stone pine (Pinus cembra), Siberian stone pine (Pinus sibirica), and Siberian dwarf pine (Pinus pumila)
Authors: Gugerli F. , Senn J. , Anzidei M. , Madaghiele A. , Büchler U. , Sperisen C. , Vendramin G. G. 
Published: March 2003

AbstractWe studied the phylogenetic relationships among the three stone pine species, Pinus cembra, P. sibirica, and P. pumila, using chloroplast microsatellites and mitochondrial nad1 intron 2 sequences. The three chloroplast microsatellite loci combined into a total of 18 haplotypes. Fourteen haplotypes were detected in 15 populations of P. cembra and one population of P. sibirica, five of which were shared between the two species, and the two populations of P. pumila comprised four species‐specific haplotypes. Mitochondrial intron sequences confirmed this grouping of species. Sequences of P. cembra and P. sibirica were identical, but P. pumila differed by several nucleotide substitutions and insertions/deletions. A repeat region found in the former two species showed no intraspecific variation. These results indicate a relatively recent evolutionary separation of P. cembra and P. sibirica, despite their currently disjunct distributions. The species‐specific chloroplast and mitochondrial markers of P. sibirica and P. pumila should help to trace the hybridization in their overlapping distribution area and to identify fossil remains with respect to the still unresolved postglacial re‐colonization history of these two species.