bluuebunny/crossref_metadata_2025 huggingface dataset:
The relationship of tutors' content expertise to interventions and perceptions in a PBL medical curriculum
Authors: Kaufman David M , Holmes D Bruce
Published: March 2003

This study addressed three questions: (1) Do content‐expert tutors differ from non‐expert tutors in the extent to which they present/explain case content? (2) Do tutors who present/explain case content differ from those who almost never do in their ratings of various outcomes of a PBL curriculum? (3) Are tutors who present/explain case content rated differently by students from tutors who almost never do? Data were gathered from 88 tutors and 168 students in the first 2 years of a PBL medical curriculum. Students assessed their tutor after each unit, and tutors completed a questionnaire near the end of the academic year. In this study, `content expertise' was defined operationally as tutors' self‐ratings on the question `To what extent could you teach (at the Med I level) the material covered in the cases?' Less than half of the tutors reported that they almost never presented/explained case content. As tutors' content expertise increased, they tended to present/explain case content more frequently. Tutors who almost never presented/explained case content rated PBL more highly than traditional methods. No differences were found in student ratings of tutors who almost never presented/explained case content, compared to tutors who did. The results suggest that tutors who are content experts find it difficult to maintain the `facilitator' role, but that those who maintain this role are more satisfied with PBL. It appears that other tutor behaviours may have a greater influence on students' ratings of their tutors.
Facility with the English Language and problem‐based learning group interaction: findings from an Arabic setting
Authors: Mpofu  , Lanphear  , Stewart  , Das  , Ridding  , Dunn
Published: March 2003

The Faculty of Medicine and Health Sciences (FMHS), United Arab Emirates (UAE) University is in a unique position to explore issues related to English language proficiency and medical student performance. All students entering the FMHS have English as a second language. This study focused on the issues of students' proficiency in English as measured by the TOEFL test, student background factors and interaction in problem‐based learning (PBL) groups. Using a modification of Bales Interaction Process Analysis, four problem‐based learning groups were observed over four thematic units, to measure the degree of student interaction within PBL groups and to compare this to individual TOEFL scores and key background variables. The students' contributions correlated highly with TOEFL test results in the giving of information (range r = 0·67–0·74). The female students adhered to interacting in English during group sessions, whereas the male students were more likely to revert to using Arabic in elaborating unclear phenomena (p < 0·01). The educational level of the student's mother was highly predictive of TOEFL scores for the male students, but not for female students. Multivariate analysis was undertaken to analyse the relative contribution of the TOEFL, parental education and years of studying in English. The best predictor of students' contributions in PBL groups was identified as TOEFL scores. The study demonstrates the importance of facilitating a locally acceptable level of English proficiency prior to admission to the FMHS. However, it also highlights the importance of not focusing only on English proficiency but paying attention to additional factors in facilitating medical students in maximizing benefits from interactions in PBL settings.
Comparison of problem‐based learning and lecture format in continuing medical education on headache diagnosis and management
Authors: Doucet  , Purdy  , Kaufman  , Langille
Published: March 2003

The purpose of the study was to compare the impact of continuing medical education for primary care physicians in Halifax, Nova Scotia, Canada, delivered through a problem‐based learning (PBL) format with that of a lecture‐based format, in the clinical area of headache diagnosis and management. From January to June 1995, 38 physicians participated in three problem‐based learning sessions, and 49 in a lecture‐based session in the clinical area of headache. Pre‐ and post‐test assessments of knowledge were made of each group before and immediately after the educational sessions. A second evaluation using Key Features Problems (KFP) to measure clinical reasoning was administered to both groups 3 months later. Analysis of covariance between groups on the post‐test, using the pre‐test result as covariate, showed significantly greater knowledge in the PBL group. Mean post‐test KFP scores also were significantly higher for the PBL group. The PBL group's satisfaction with several programme dimensions was significantly higher than that of the lecture group. These results must be viewed in the context of differing amounts of exposure for the two groups. Problem‐based learning in continuing medical education in the area of headache management was associated with greater knowledge acquisition and with greater improvement in clinical reasoning skills than in a lecture‐based approach. Problem‐based learning also was preferred by family physicians. However, the cost–benefit of this approach was questioned, since the PBL group had more exposure. Several factors limit the generalizability of this study, e.g. the impossibility of randomly composing the two experimental groups. Further research is required to determine if the results are generalizable and whether a PBL approach results in change in practice behaviour.
Clinical experience of medical students in primary care: use of an electronic log in monitoring experience and in guiding education in the Cambridge Community Based Clinical Course
Authors: Alderson  , Oswald
Published: March 2003

Objectives

The amount of medical student teaching in the community has increased markedly recently, but uncertainties remain about whether there is sufficient clinical material to meet students’ learning needs and, if so, how best to monitor the experience and ensure that students are benefiting from it.

Design

On the Cambridge Community Based Clinical Course, a 15‐month attachment in primary care, the students used hand‐held computers to monitor their clinical experience as it developed.

Setting

The General Practice and Primary Care Research Unit, Cambridge, UK.

Subjects

Medical students.

Results

Thirteen students recorded 8140 contacts over 4 years. Contacts recorded by students over 15 months varied between 256 and 1153. Eight specialities each contributed more than 5% of total experience. These were general medicine, 26·9% (range 23·8%–36·6%), obstetrics and gynaecology, 11·3% (range 7·2%–17·1%), orthopaedics and rheumatology, 11·3% (range 3·7%–15·2%), paediatrics, 10·7% (range 4·1%–19·8%), ENT, 7·4% (range 3·3%–10·2%), dermatology, 7·1% (range 4%–10·1%), psychiatry, 6·4% (range 5%–9·7%) and general surgery, 6·4% (range 1·1%–9·9%).

Conclusions

The results show that it is possible to get a broad and varied exposure to clinical problems on a long‐term community‐based course. However, as a consequence of the opportunistic way in which clinical experience is obtained on a community attachment, individual students often had gaps in their experience. The logs provided a means for identifying these gaps so that action could be taken to address them. The logs themselves proved to be a practical and feasible way to record student experience as it unfolded.
One year's experience with a clinical skills resource centre
Authors: Bradley Paul , Bligh John
Published: March 2003

Objectives

To describe our experience of teaching clinical skills to first‐year medical students in a new problem‐based curriculum.

Design

Prospective evaluation of clinical skills acquisition using objective measures.

Setting

Students were taught in a purpose‐designed clinical skills resource centre in weekly structured sessions.

Subjects

All 210 first year medical undergraduates in the first year of a new problem‐based and clinically oriented course.

Results

Student performance in structured objective examinations improved over 1 year. In all but one of nine matched stations, involving history, examination and procedural skills, improvements were significant. Ninety‐three per cent thought that the appropriateness of the skills training course to other course elements was `good' or `very good'.

Conclusions

First‐year medical students can learn a wide range of clinical skills. Integrated teaching of clinical skills improves satisfaction with undergraduate studies.
The distribution and frequency of microsatellite loci inDrosophila melanogaster
Authors: SCHUG M. D. , WETTERSTRAND K. A. , GAUDETTE M. S. , LIM R. H. , HUTTER C. M. , AQUADRO C. F.
Published: March 2003

We report the results of a comprehensive search ofDrosophila melanogasterDNA sequences in GenBank for di‐, tri‐, and tetranucleotide repeats of more than four repeat units, and a DNA library screen for dinucleotide repeats. Dinucleotide repeats are more abundant (66%) than tri‐ (30%) or tetranucleotide (4%) repeats. We estimate that 1917 dinucleotide repeats with 10 or more repeat units are present in the euchromaticD. melanogastergenome and, on average, they occur once every 60 kb. Relative to many other animals, dinucleotide repeats inD. melanogasterare short. Tri‐ and tetranucleotide repeats have even fewer repeat units on average than dinucleotide repeats. Our WorldWide Web site (http://www.bio.cornell.edu/genetics/aquadro/aquadro.html) posts the complete list of 1298 microsatellites (≥ five repeat units) identified from the GenBank search. We also summarize assay conditions for 70D. melanogastermicrosatellites characterized in previous studies and an additional 56 newly characterized markers.
The genetic structure of swarms and the timing of their production in the queen cycles of neotropical wasps
Authors: STRASSMANN JOAN E. , GOODNIGHT KEITH F. , KLINGLER CEAL J. , QUELLER DAVID C.
Published: March 2003

Kin selection theory has received some of its strongest support from analyses of within‐colony conflicts between workers and queens in social insects. One of these conflicts involves the timing of queen production. In neotropical wasps, new queens are only produced by colonies with just one queen while males are produced by colonies with more queens, a pattern favoured by worker interests. We now show that new colonies, or swarms, have few queens and variable within‐colony relatednesses which means that their production is not tied to new queen production. The queens in these swarms are seldom the mothers of the workers in the swarm. Therefore, either colonies producing swarms have very many queens, or queens joining daughter swarms are reproductive losers on the original colonies. As new colony production is not linked to queen production, it can occur at the ecologically optimum time, i.e. the rainy season. This disassociation between queen production and new colony production allows worker interests in sex ratios to prevail without hampering new colony production at the most favourable season, an uncoupling that may contribute to the ecological success of the Epiponini.
Sex after all: high levels of diversity detected in the arctic clonal plant Saxifraga cernua using RAPD markers
Authors: GABRIELSEN T. M. , BROCHMANN C.
Published: March 2003

Arctic plants in general and arctic clonal plants in particular have often been assumed to contain low levels of genetic diversity. We used RAPDs (random amplified polymorphic DNAs) to investigate genetic diversity in the arctic‐alpine Saxifraga cernua, which mainly reproduces clonally via bulbils, at three spatial scales in Svalbard: (i) ‘macroscale’, between two sites 11 km apart; (ii) ‘mesoscale’, along two crossing transects at each site; and (iii) ‘microscale’, within a 3 × 3 m square at each site. Thirteen putative clones (RAPD phenotypes) were distinguished among 93 ramets based on 38 RAPD markers. The genetic diversity (D; mean 0.52, range 0.10–0.81) and evenness (E; mean 0.42, range 0.00–0.82) were at the same level as in clonal plants in general. However, the diversity strongly depended on site and spatial scale. Several clones were highly divergent and clustered independently of site in UPGMA and PCO analyses. In an analysis of molecular variance (AMOVA), most of the variation (59%) was found within sites. Mantel tests revealed no correlation between spatial and genetic distance within sites. Our results suggest that occasional sexual reproduction as well as clonal migration via bulbil dispersal play a significant role in the treeless arctic environment, where S. cernua is widespread and locally very abundant. In contrast, Bauert et al. (Molecular Ecology 7, 1519–1527) found no genetic variation within populations or regions of the Alps, where the species has highly isolated occurrences.
The identification of a sex‐specific DNA marker in the ostrich using a random amplified polymorphic DNA (RAPD) assay
Authors: Bello N. , Sánchez A.
Published: March 2003

PCR‐based techniques described to date for sex diagnosis in birds are not useful in ratites. We report here the identification of a W‐linked marker in the ostrich (Struthio camelus) which allows gender diagnosis in chicks or juvenile birds. DNA from 10 females and 11 males was used to prepare two pools for each sex. Two‐hundred different 10‐mer primers of arbitrary sequence were used to screen those pools using a random amplified polymorphic DNA (RAPD) assay. One primer (D 10) generated a female‐specific band. Sex specificity was confirmed by testing the 21 animals individually. The candidate DNA fragment was cloned and sequenced. Longer primers were designed to optimize a sex‐specific PCR which will be useful in diagnosis.
Reproductive mode and population genetic structure of the cereal aphid Sitobion avenae studied using phenotypic and microsatellite markers
Authors: Simon J.‐C. , Baumann S. , Sunnucks P. , Hebert P. D. N. , Pierre J.‐S. , Le Gallic J.‐F. , Dedryver C.‐A.
Published: March 2003

As French populations of the aphid Sitobion avenae exhibit a range of reproductive modes, this species provides a good opportunity for studying the evolution of breeding system variation. The present analysis combined ecological and genetic investigations into the spatial distribution of variation in reproductive mode. Reproductive mode was characterized in 277 lineages of S. avenae from France, and these aphids were scored for five microsatellite loci. The analyses revealed strong geographical partitioning of breeding systems, with obligate asexuals mostly restricted to the south of France, while lineages producing sexual forms were more common in the north. Contrary to what might be anticipated for organisms with frequent parthenogenesis, there was substantial genic and genotypic diversity, even in the obligately asexual lineages. More than 120 different genotypes were detected among the 277 aphid lineages, with an average of 5.9 alleles per locus (range four to 16) and heterozygosity of 56.7%. As with previous studies of allozyme variation in aphids, most loci showed heterozygote deficits, and disequilibrium was common among allelic variants at different loci, even after removal of replicate copies of genotypes that might have been derived through clonal reproduction. Our results suggest that selection is important in structuring reproductive systems and genetic variation in French S. avenae. Canonical correspondence analysis was employed to examine the associations between genotypic and phenotypic variables, enabling the identification of alleles correlated with life‐history traits.
Major histocompatibility complex (MHC) class II polymorphism and paternity in the monogamousHypogeomys antimena, the endangered, largest endemic Malagasy rodent
Authors: Sommer S. , Tichy H.
Published: March 2003

Sequence variation at a major histocompatibility complex (MHC) class II gene was examined inHypogeomys antimena, a monogamous endemic rodent of Madagascar. The study was conducted throughout its remaining geographical range (20 × 40 km) by direct sequencing and single‐strand conformation polymorphism (SSCP). The objectives of the study were: (i) to investigate levels of polymorphism in the MHC complex of a highly endangered species that experienced a severe reduction in population size; and (ii) to investigate the genetic mating system by assessing the frequency of extra‐pair paternity (EPP) as EPP might have important consequences to increase gene flow and, therefore, genetic variability within a population. The amplified gene segment had a very low variability (only two alleles) inH. antimenacompared with other mammalian species. The alleles segregated consistently with Mendelian expectations in families. No case of EPP was found. The present data suggest no difference between the social and the genetic mating system.
Phylogeography and conservation genetics of the Iowa Pleistocene snail
Authors: Ross T. K.
Published: March 2003

The Iowa Pleistocene snail, Discus macclintocki, is an endangered species that survives only in relictual populations on algific (cold‐air) talus slopes in northeast Iowa and northwest Illinois in the central region of the USA. These populations are believed to have been isolated since the temperatures began to warm at the end of the last glacial period around 16 500 years ago. DNA sequencing of the 16s rRNA gene of the mitochondria was used to determine the genetic relationship among 10 populations and the genetic diversity within these populations. Genetic diversity is extremely high within this species with 40 haplotypes spread across the 10 populations sampled within a 4000 km2 region. Phylogenetic analyses showed that haplotypes formed monophyletic groups by the watershed on which they were found, suggesting that watersheds were important historical avenues of gene flow. Genetic distances were strongly related to the geographical distance among all populations, but this relationship was dependent on the scale being considered.
Differentiation between natural and cultivated populations of Medicago sativa (Leguminosae) from Spain: analysis with random amplified polymorphic DNA (RAPD) markers and comparison to allozymes
Authors: Jenczewski Eric , Prosperi Jean Marie , Ronfort Joëlle
Published: March 2003

The conservation of a crop’s wild relatives as genetic resources requires an understanding of the way genetic diversity is maintained in their populations, notably the effect of crop‐to‐wild gene flow. In this study, the amount of differentiation between natural and cultivated populations of Medicago sativa was analysed using random amplified polymorphic DNA (RAPD) markers and an extension of the amova procedure adapted to autotetraploid organisms. Simulations of structured populations were performed to test whether amova provides estimates of population structure in autotetraploids that can be directly compared to those obtained for allozyme data. Simulations showed that φ‐statistics allow a good estimation of population differentiation when unbiased allelic frequencies are used to correct the conditional expectations of squared genetic distances. But such unbiased estimates can not be practically guaranteed, and population structure is notably overestimated when some populations are fixed for the presence of amplified fragments. However, removing fixed loci from the data set improves the statistical power of the test for population structure. The genetic variation of 15 natural and six cultivated populations of M. sativa was analysed at 25 RAPD loci and compared to estimates computed with allozymes on the same set of populations. Although RAPD markers revealed less within‐population genetic diversity than allozymes, the quantitative and qualitative patterns of population structure were in full agreement with allozymes. This confirmed the conclusions drawn from the allozymic survey: crop‐to‐wild gene flow occurred in many locations, but some other mechanisms opposed cultivated traits to be maintained into natural populations.
Genetic variation within and among populations of the threatened lichenLobaria pulmonariain Switzerland and implications for its conservation
Authors: Zoller S. , Lutzoni F. , Scheidegger C.
Published: March 2003

The foliose epiphytic lichenLobaria pulmonariahas suffered a significant decline in European lowlands during the last decades and therefore is considered as endangered throughout Europe. An assessment of the genetic variability is necessary to formulate biologically sound conservation recommendations for this species. We investigated the genetic diversity of the fungal symbiont ofL. pulmonariausing 143 specimens sampled from six populations (two small, one medium, three large) in the lowland, the Jura Mountains, the pre‐Alps and the Alps of Switzerland. Among all nuclear and mitochondrial regions sequenced for this study, variability was found only in the internal transcribed spacer (ITS I), with three polymorphic sites, and in the nuclear ribosomal large subunit (nrLSU), with four polymorphic sites. The variable sites in the nrLSU are all located within a putative spliceosomal intron. We sequenced these two regions for 81 specimens and detected six genotypes. Two genotypes were common, two were found only in the more diverse populations and two were found only in one population each. There was no correlation between population size and genetic diversity. The highest genetic diversity was found in populations where the fungal symbiont is reproducing sexually. Populations with low genetic diversity included only the two same common genotypes. Our study provides evidence suggesting thatL. pulmonariais self‐incompatible and heterothallic. Based on our results we give populations with sexually reproducing individuals a higher rank in terms of conservation priority than strictly asexual populations. The remaining lowland populations are so small, that one single catastrophic event such as a windthrow might destroy the entire population. Hence we suggest augmenting such populations in size and genetic diversity using small thallus fragments or vegetative diaspores collected in other populations. As we did not detect any locally adapted genotypes, these transplants can be taken from any other genetically diverse population in Switzerland.
Variation on islands: major histocompatibility complex (Mhc) polymorphism in populations of the Australian bush rat
Authors: Seddon J. M. , Baverstock P. R.
Published: March 2003

Loss of genetic variation in small, isolated populations is commonly observed at neutral or nearly neutral loci. In this study, the loss of genetic variation was assessed in island populations for a locus of major histocompatibility complex (Mhc), a locus shown to be under the influence of balancing selection. A total of 36 alleles was found at the second exon ofRT1.Bain 14 island and two mainland populations ofRattus fuscipes greyii. Despite this high overall diversity, a substantial lack of variation was observed in the small island populations, with 13 islands supporting only one to two alleles. Two populations, Waldegrave and Williams Islands, showed moderately high levels of heterozygosity (52–56%) which were greater than expected under neutrality, suggesting the action of balancing selection. However, congruence between the level of variation at thisMhclocus and in previous allozyme electrophoresis and mitochondrial DNA studies highlights the dominant influence of genetic drift and population factors, such as bottlenecks and structuring in the founding population, in the loss of genetic variation in these small, isolated populations.
Assessment of natural and artificial propagation of the white‐clawed crayfish (Austropotamobius pallipes species complex) in the Alpine region with nuclear and mitochondrial markers
Authors: Largiadèr C. R. , Herger F. , Lörtscher M. , Scholl A.
Published: March 2003

In a joint analysis of nuclear (allozyme) and mitochondrial markers (sequence and restriction fragment length polymorphism (RFLP) analysis of the 12S and 16S genes), five genetically distinct groups of the Austropotamobius pallipes Lereboullet species complex were detected in the Alpine region. The geographical distribution of these evolutionary lineages coincided largely with several taxa (A.p. pallipes, A. berndhauseri, A.(p.) italicus) formerly defined on the basis of morphological characters. A low level of genetic variability was found within these lineages. For some populations, the combination of the two markers gave additional information about the likelihood of their natural or artificial origin. A hybrid zone was detected between A.p. pallipes and A. berndhauseri in the Lake Geneva area. The mosaic distribution of the five evolutionary lineages indicated that conservation efforts should be aimed at the level of local populations.
Phylogeography, intraspecific structure and sex‐biased dispersal of Dall’s porpoise, Phocoenoides dalli, revealed by mitochondrial and microsatellite DNA analyses
Authors: Escorza‐Treviño S. , Dizon A. E.
Published: March 2003

Mitochondrial DNA (mtDNA) control‐region sequences and microsatellite loci length polymorphisms were used to estimate phylogeographical patterns (historical patterns underlying contemporary distribution), intraspecific population structure and gender‐biased dispersal of Phocoenoides dalli dalli across its entire range. One‐hundred and thirteen animals from several geographical strata were sequenced over 379 bp of mtDNA, resulting in 58 mtDNA haplotypes. Analysis using FST values (based on haplotype frequencies) and ΦST values (based on frequencies and genetic distances between haplotypes) yielded statistically significant separation (bootstrap values P < 0.05) among most of the stocks currently used for management purposes. A minimum spanning network of haplotypes showed two very distinctive clusters, differentially occupied by western and eastern populations, with some common widespread haplotypes. This suggests some degree of phyletic radiation from west to east, superimposed on gene flow. Highly male‐biased migration was detected for several population comparisons. Nuclear microsatellite DNA markers (119 individuals and six loci) provided additional support for population subdivision and gender‐biased dispersal detected in the mtDNA sequences. Analysis using FST values (based on allelic frequencies) yielded statistically significant separation between some, but not all, populations distinguished by mtDNA analysis. RST values (based on frequencies of and genetic distance between alleles) showed no statistically significant subdivision. Again, highly male‐biased dispersal was detected for all population comparisons, suggesting, together with morphological and reproductive data, the existence of sexual selection. Our molecular results argue for nine distinct dalli‐type populations that should be treated as separate units for management purposes.
Is the Gibraltar Strait a barrier to gene flow for the bat Myotis myotis (Chiroptera: Vespertilionidae)?
Authors: Castella V. , Ruedi M. , Excoffier L. , Ibáñez C. , Arlettaz R. , Hausser J.
Published: March 2003

Because of their role in limiting gene flow, geographical barriers like mountains or seas often coincide with intraspecific genetic discontinuities. Although the Strait of Gibraltar represents such a potential barrier for both plants and animals, few studies have been conducted on its impact on gene flow. Here we test this effect on a bat species (Myotis myotis) which is apparently distributed on both sides of the strait. Six colonies of 20 Myotis myotis each were sampled in southern Spain and northern Morocco along a linear transect of 1350 km. Results based on six nuclear microsatellite loci reveal no significant population structure within regions, but a complete isolation between bats sampled on each side of the strait. Variability at 600 bp of a mitochondrial gene (cytochrome b) confirms the existence of two genetically distinct and perfectly segregating clades, which diverged several million years ago. Despite the narrowness of the Gibraltar Strait (14 km), these molecular data suggest that neither males, nor females from either region have ever reproduced on the opposite side of the strait. Comparisons of molecular divergence with bats from a closely related species (M. blythii) suggest that the North African clade is possibly a distinct taxon warranting full species rank. We provisionally refer to it as Myotis cf punicus Felten 1977, but a definitive systematic understanding of the whole Mouse‐eared bat species complex awaits further genetic sampling, especially in the Eastern Mediterranean areas.
Monitoring gene flow from transgenic sugar beet using cytoplasmic male‐sterile bait plants
Authors: Saeglitz Christiane , Pohl Matthias , Bartsch Detlef
Published: March 2003

One of the most discussed environmental effects associated with the use of transgenic plants is the flow of genes to plants in the environment. The flow of genes may occur through pollen since it is the reproductive system that is designed for gene movement. Pollen‐mediated gene escape is hard to control in mating plants. Pollen from a wind pollinator can move over distances of more than 1000 m. To investigate the efficiency of transgenic pollen movement under realistic environmental conditions, the use of bait plants might be an effective tool. In this study, cytoplasmic male‐sterile (CMS) sugar beets were tested with regard to their potential for monitoring transgene flow. As the pollen source, transgenic sugar beets were used that express recombinant DNA encoding viral (beet necrotic yellow vein virus) resistance, and antibiotic (kanamycin) and herbicide (glufosinate) tolerance genes. In a field trial, the effectiveness of a hemp (Cannabis sativa) stripe containment strategy was tested by measuring the frequency of pollinated CMS bait plants placed at different distances and directions from a transgenic pollen source. The results demonstrated the ineffectiveness of the containment strategy. Physiological and molecular tests confirmed the escape and production of transgenic offspring more than 200 m behind the hemp containment. Since absolute containment is unlikely to be effective, the CMS–bait plant detection system is a useful tool for other monitoring purposes.
Molecular genetic markers provide no evidence for reproductive isolation among retreat building phenotypes of the net‐spinning caddisfly Macrostemumcarolina
Authors: Plague G. R. , Mulvey M. , Glenn T. C. , Mcarthur J. V.
Published: March 2003

Larvae of the stream‐dwelling, filter‐feeding caddisfly Macrostemumcarolina construct silken catchnets within protective retreats. In the Savannah River, M. carolina individuals make three different retreats, each with a distinct water entrance hole: (i) at the end of a silken tube; (ii) with a ≈180° silken backstop; and (iii) flush with the top of the retreat. To resolve whether these different retreats represent alternative behavioural phenotypes within a single panmictic population or fixed phenotypes within three genetically distinct populations or species, we compared the allele frequencies at three polymorphic nuclear loci (allozyme electrophoresis for Gpi, Mpi and Pgm) and the mitochondrial DNA (mtDNA) haplotype frequencies among individuals displaying the three retreat morphs. We also calculated pairwise exact tests of population differentiation using the allozyme and mtDNA allele frequencies. No significant genetic differentiation was detected among caddisflies exhibiting the different retreat morphs. Therefore, these morphs apparently represent a single panmictic population in the Savannah River. Consequently, additional study is required to assess whether this retreat polymorphism is a phenotypically plastic trait under conditional control, or is mediated by alternative alleles at a Mendelian gene or genes (or a combination of the two).
Divergence between two Antarctic species of the ciliate Euplotes, E. focardii and E. nobilii, in the expression of heat‐shock protein 70 genes
Authors: La Terza A. , Papa G. , Miceli C. , Luporini P.
Published: March 2003

Most organisms oppose many environmental stresses by rapidly enhancing synthesis of the highly conserved Hsp70 family of heat‐shock proteins. Two ciliates which are endemic in Antarctic coastal seawater, Euplotes focardii and E. nobilii, and behave as psychrophile and psychrotroph micro‐organisms, respectively, revealed a divergence in the capacity to respond to thermal stress with an activation of the transcription of their hsp70 genes. In both species, these genes were shown to be represented by thousands of copies in the cell’s somatic functional nucleus (macronucleus). However, while a strong transcriptional activity of hsp70 genes was induced in E. nobilii cells transferred from 4 to 20 °C, a much smaller increase was revealed in heat‐shocked cells of E. focardii. These findings suggest a closer adaptation to the stably cold Antarctic waters in the genetic response of E. focardii to thermal stress.
Pollen pool heterogeneity in shortleaf pine, Pinus echinata Mill.
Authors: Dyer R. J. , Sork V. L.
Published: March 2003

Pollen is the dominant vector of gamete exchange for most temperate tree species. Because pollen movement influences the creation, maintenance and erosion of genetic structure in adult populations, it is important to understand what factors influence the process of pollen movement. Isolation by distance in pollen donor populations can create highly structured pollen polls by increased sampling of local fathers. Extrinsic factors, such as the intervening vegetative structure and local pollen donor densities, can also influence the genetic composition of local pollen pools. Using paternally inherited chloroplast microsatellite markers, we examined the structure and diversity of pollen pools in Pinus echinata Mill. in southern Missouri, USA. Our analysis is based on a multivariate amova analysis of stands (≈ 1 ha; six per region) nested within regions (≈ 800 ha; four each). Significant multilocus structure of the pollen pool within regions (φSR = 0.095), but not among regions (φRT = 0.010), indicates that pollen movement is relatively restricted. Furthermore, the significant correlation between pairwise genetic and physical distances (Mantel correlation; ρ = 0.32) provided support for the isolation by distance hypothesis. Our results indicated that availability of pollen donors did not affect diversity of the pollen pool, measured by the number of unique multilocus genotypes at each stand. However, pollen pool diversity was negatively associated with vegetative structure, measured as total forest tree density. Our findings indicated that on‐going pollen movement within continuous forest is relatively restricted as a result of both isolation by distance and vegetative structure.
Genetic structure of brown trout (Salmo trutta, L.) populations from south‐western France: data from mitochondrial control region variability
Authors: Aurelle D. , Berrebi P.
Published: March 2003

The genetic relationships between several French Atlantic populations of brown trout were analysed using polymerase chain reaction–single‐strand conformation polymorphism and sequencing of two parts of the mitochondrial control region. Ten mitochondrial haplotypes were identified, separated by a small number of mutations. The distribution of these haplotypes confirmed our hypothesis of the existence of two genetically well‐differentiated groups of populations in this area, which has already been suggested using nuclear markers. Nuclear and mitochondrial markers, however, show different patterns of genetic differentiation: some populations which belong to one group according to allozyme results appear to be part of the other when using mitochondrial DNA. The origin of these different forms is discussed; they seem to belong to the Atlantic grouping. Nevertheless, the hypothesis of an ancestral and a modern form suggested for northern populations does not appear valid in this particular case.
Insertion polymorphism of retrotransposable elements in populations of the insular, endemic species Drosophila madeirensis
Authors: Lepetit D. , Brehm A. , Fouillet P. , Biémont C.
Published: March 2003

The insertion site numbers of the retrotransposable elements (TE) 412, gypsy and bilbo were determined in individuals of five distinct natural populations of the endemic species Drosophila madeirensis from the island of Madeira. The TE distributions were compared to those of the paleartic, widespread and phylogenetically closely related species, D. subobscura. In situ hybridization and Southern blots showed that in D. madeirensis the number of insertion sites ranged between 10 and 15, three and six, and 35 and 42 for elements 412, gypsy and bilbo, respectively. The corresponding values for D. subobscura were similar. Two of these elements, 412 and gypsy, had very few insertions in the heterochromatin, unlike bilbo, which displayed a high heterochromatic insertion number. The Southern band polymorphism was very high, leading to within‐population variation of 97.2%, whatever the population and the TE concerned. Using the polymorphic TE insertion sites as markers to analyse population structure by amova, adapted for RAPD (Randomly Amplified Polymorphic DNA) data, we found small but significant genetic differences between the populations on Madeira. This slight differentiation, coupled with similar copy numbers for each TE between populations, suggests that the D. madeirensis species consists of a single, only slightly subdivided population. These data also show that insular populations and endemic species of Drosophila can have as many copies of TEs as more widespread species.
Noninvasive molecular tracking of colonizing wolf (Canis lupus) packs in the western Italian Alps
Authors: Lucchini V. , Fabbri E. , Marucco F. , Ricci S. , Boitani L. , Randi E.
Published: March 2003

We used noninvasive methods to obtain genetic and demographic data on the wolf packs (Canis lupus), which are now recolonizing the Alps, a century after their eradication. DNA samples, extracted from presumed wolf scats collected in the western Italian Alps (Piemonte), were genotyped to determine species and sex by sequencing parts of the mitochondrial DNA (mtDNA) control‐region and ZFX/ZFY genes. Individual genotypes were identified by multilocus microsatellite analyses using a multiple tubes polymerase chain reaction (PCR). The performance of the laboratory protocols was affected by the age of samples. The quality of excremental DNA extracts was higher in samples freshly collected on snow in winter than in samples that were older or collected during summer. Preliminary mtDNA screening of all samples allowed species identification and was a good predictor of further PCR performances. Wolf, and not prey, DNA targets were preferentially amplified. Allelic dropout occurred more frequently than false alleles, but the probability of false homozygote determinations was always < 0.001. A panel of six to nine microsatellites would allow identification of individual wolf genotypes, also whether related, with a probability of identity of < 0.015. Genealogical relationships among individuals could be determined reliably if the number of candidate parents was 6–8, and most of them had been sampled and correctly genotyped. Genetic data indicate that colonizing Alpine wolves originate exclusively from the Italian source population and retain a high proportion of its genetic diversity. Spatial and temporal locations of individual genotypes, and kinship analyses, suggest that two distinct packs of closely related wolves, plus some unrelated individuals, ranged in the study areas. This is in agreement with field observations.
Phylogeography of the common ivy (Hedera sp.) in Europe: genetic differentiation through space and time
Authors: Grivet D. , Petit R. J.
Published: March 2003

We studied the phylogeography of ivy (Hedera sp.), a liana widespread in Europe, throughout its natural range. The populations sampled belong to four closely related species differing by ploidy levels and morphological characters. Chloroplast (cp) markers were used and 13 haplotypes were detected, usually shared across species, contrary to ribosomal internal transcribed spacer (ITS) variants. We demonstrated the existence of a strong overall cpDNA phylogeographical structure. Several methods of data analysis were conducted to describe how this structure and the genetic diversity change through space and time. Southern populations, especially those from Spain, are the most divergent. Pairwise estimates of differentiation point to isolation by distance, and the existence of a latitudinal gradient of divergence was demonstrated using a regression procedure. Similarly, latitudinal differences in haplotype richness and diversity exist, as shown by population permutations (‘differentiation through space’). Finally, we measured differentiation by taking into account successive levels of divergence between haplotypes (‘differentiation through time’). Genetic differentiation turns out to be much greater when differences between closely related haplotypes are not considered. Further, these results indicate that the phylogeographical structure is essentially due to the relative distribution of the most similar haplotypes. Diversity decreases from south to north, whereas haplotype frequencies change longitudinally. It appears that Hedera survived in Spanish and Balkan refugia during the last ice age. A third refugium must have been present in the Alps or in Italy. During the northward expansion, the decrease in overall diversity was attenuated by some mixing of lineages at intermediate latitudes, resulting in comparatively higher levels of differentiation in the south.
Recent changes in phenotype and patterns of host specialization in Wolbachia bacteria
Authors: Jiggins Francis M. , Bentley Joanna K. , Majerus Michael E. N. , Hurst Gregory D. D.
Published: March 2003

Wolbachia are a genus of bacterial symbionts that are known to manipulate the reproduction of their arthropod hosts, both by distorting the host sex ratio and by inducing cytoplasmic incompatibility. Previous work has suggested that some Wolbachia clades specialize in particular host taxa, but others are diverse. Furthermore, the frequency with which related strains change in phenotype is unknown. We have examined these issues for Wolbachia bacteria from Acraea butterflies, where different interactions are known in different host species. We found that bacteria from Acraea butterflies mostly cluster together in several different clades on the bacterial phylogeny, implying specialization of particular strains on these host taxa. We also observed that bacterial strains with different phenotypic effects on their hosts commonly shared identical gene sequences at two different loci. This suggests both that the phenotypes of the strains have changed recently between sex ratio distortion and cytoplasmic incompatibility, and that host specialization is not related to the bacterial phenotype, as suggested from previous data. We also analysed published data from other arthropod taxa, and found that the Wolbachia infections of the majority of arthropod genera tend to cluster together on the bacterial phylogeny. Therefore, we conclude that Wolbachia is most likely to move horizontally between closely related hosts, perhaps because of a combination of shared vectors for transmission and physiological specialization of the bacteria on those hosts.
Communities and populations of sebacinoid basidiomycetes associated with the achlorophyllous orchid Neottia nidus‐avis (L.) L.C.M. Rich. and neighbouring tree ectomycorrhizae
Authors: Selosse Marc‐André , WEIß Michael , Jany Jean‐Luc , Tillier Annie
Published: March 2003

Several achlorophyllous orchids associate with ectomycorrhizal hymenomycetes deriving carbon from surrounding trees for the plant. However, this has not been shown for achlorophyllous orchids associating with species of Rhizoctonia, a complex of basal lineages of hymenomycetes that are the most common orchid partners. We analysed Neottia nidus‐avis, an achlorophyllous orchid symbiotic with a Rhizoctonia, to identify its symbionts by internal transcribed spacer (ITS) sequencing. Analysis of 61 root systems from 23 French populations showed that N. nidus‐avis associates highly specifically with a group of species of Sebacinaceae. Their diversity emphasizes the need for further investigations in the Sebacinaceae systematics. Sebacinoid ITS sequences were often identical within orchid populations and a trend to regional variation in symbionts was observed. Using ITS and intergenic spacer (IGS) polymorphism, we showed that each root system harboured a single species, but that several genets colonized it. However, no polymorphism of these markers was found among portions of each root: this is consistent with the putative mode of entry of the fungus, i.e. from the rhizome into roots but not repeatedly from the soil. In addition, ectomycorrhizae were always found within the N. nidus‐avis root systems: 120 of the 144 ectomycorrhizae typed by ITS sequencing were colonized by a sebacinoid fungus identical in ITS sequence to the respective orchid symbiont (even for the IGS polymorphism in some cases). Because sebacinoids were demonstrated recently to be ectomycorrhizal, the orchid is likely to derive its resources from surrounding trees, a mycorrhizal cheating strategy similar to other myco‐heterotrophic plants studied to date.
The leatherback turtle, Dermochelys coriacea, exhibits both polyandry and polygyny
Authors: Crim J. L. , Spotila L. D. , Spotila J. R. , O'Connor M. , Reina R. , Williams C. J. , Paladino F. V.
Published: March 2003

The leatherback turtle (Dermochelys coriacea) is an endangered species, and world‐wide populations are declining. To understand better the mating structure of this pelagic and fragile species, we investigated paternity in nearly 1000 hatchlings from Playa Grande in Parque Marino Nacional Las Baulas, Costa Rica. We collected DNA samples from 36 adult female leatherbacks and assessed allele frequency distributions for three microsatellite loci. For 20 of these 36 females, we examined DNA from hatchlings representing multiple clutches, and in some cases assessed up to four successive clutches from the same female. We inferred paternal alleles by comparing maternal and hatchling genotypes. We could not reject the null hypothesis of single paternity in 12 of 20 families (31 of 50 clutches), but we did reject the null hypothesis in two families (eight of 50 clutches). In the remaining six families, the null hypothesis could not be accepted or rejected with certainty because the number of hatchlings exhibiting extra nonmaternal alleles was small, and could thus be a result of mutation or sample error. Successive clutches laid by the same female had the same paternal allelic contribution, indicating sperm storage or possibly monogamy. None of 20 females shared the same three‐locus genotype whereas there were two instances of shared genotypes among 17 inferred paternal three‐locus genotypes. We conclude that both polyandry and polygyny are part of the mating structure of this leatherback sea turtle population.