bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal activity patterns of Ixodes pacificus nymphs in relation to climatic conditions
Authors: EISEN L. , EISEN R. J. , LANE R. S.
Published: March 2003

Abstract In western North America, the tick Ixodes pacificus Cooley & Kohls (Acari: Ixodidae) is the primary vector to humans and domestic animals of the disease agents causing Lyme disease and granulocytic ehrlichiosis. We examined the seasonal activity patterns of I. pacificus nymphs over a 4‐year period, including the wet and cold El Niño winter/spring of 1998, in a dry oak/madrone woodland, and for one year in a cooler and moister redwood/tanoak woodland in Mendocino County, California. Linear regressions were used to estimate when nymphal densities first exceeded and then fell below 25, 50 and 75% of the recorded yearly peak densities. In oak/madrone woodland, nymphs typically were active by mid‐March, reached 50% of their yearly peak densities in early to mid‐April, peaked by early May, fell below 50% of their peak densities by early to mid‐June, and were absent by late July to mid‐August. The lengths of the periods with nymphal densities exceeding 50 and 75% of the recorded yearly peaks in oak/madrone woodland were associated positively with rainfall and negatively with maximum air temperatures during April–May. Moreover, nymphal numbers typically reached 50% of their peak 10–15 days later, remained at levels above 50% of the peak 1.3–1.5 times longer, and started declining 4–6 weeks later under cooler, moister climatic conditions (oak/madrone woodland in 1998 and redwood/tanoak woodland in 2000) relative to warmer, drier conditions (oak/madrone woodland in 2000–2001). In oak/madrone woodland, nymphal densities typically started to decline when mean maximum daily air temperatures exceeded 23°C. Nymphal densities were higher in dry oak/madrone relative to moist redwood/tanoak woodland from mid‐March to late May 2000, similar in both habitat types in early June, but higher in redwood/tanoak woodland from late June onwards. We conclude that large‐scale studies of the density of I. pacificus nymphs in California need to consider spatial variation in the length of nymphal activity periods and select temporal sampling regimens that yield representative data for all included habitat types.
Stream‐bank shade and larval distribution of the Philippine malaria vector Anopheles flavirostris
Authors: Foley D. H. , Torres E. P. , Mueller I.
Published: March 2003

Abstract The principal malaria vector in the Philippines, Anopheles flavirostris (Ludlow) (Diptera: Culicidae), is regarded as ‘shade‐loving’ for its breeding sites, i.e. larval habitats. This long‐standing belief, based on circumstantial observations rather than ecological analysis, has guided larval control methods such as ‘stream‐clearing’ or the removal of riparian vegetation, to reduce the local abundance of An. flavirostris. We measured the distribution and abundance of An. flavirostris larvae in relation to canopy vegetation cover along a stream in Quezon Province, the Philippines. Estimates of canopy openness and light measurements were obtained by an approximation method that used simplified assumptions about the sun, and by hemispherical photographs analysed using the program hemiphot©. The location of larvae, shade and other landscape features was incorporated into a geographical information system (GIS) analysis.

Early larval instars of An. flavirostris were found to be clustered and more often present in shadier sites, whereas abundance was higher in sunnier sites. For later instars, distribution was more evenly dispersed and only weakly related to shade. The best predictor of late‐instar larvae was the density of early instars. Distribution and abundance of larvae were related over time (24 days). This pattern indicates favoured areas for oviposition and adult emergence, and may be predictable. Canopy measurements by the approximation method correlated better with larval abundance than hemispherical photography, being economical and practical for field use.

Whereas shade or shade‐related factors apparently have effects on larval distribution of An. flavirostris, they do not explain it completely. Until more is known about the bionomics of this vector and the efficacy and environmental effects of stream‐clearing, we recommend caution in the use of this larval control method.
Pyrethroid resistance in tropical bedbugs, Cimex hemipterus, associated with use of treated bednets
Authors: Myamba J. , Maxwell C. A. , Asidi A. , Curtis C. F.
Published: March 2003

Abstract When Tanzanian villages were provided with pyrethroid‐treated bednets, bedbugs (Cimicidae) disappeared; however, after about 6 years they have re‐appeared in these villages. Using a newly devised test‐kit, susceptibility tests of bedbugs Cimex hemipterus (Fabricius) from five of these villages showed that there is resistance to permethrin and alphacypermethrin in bedbugs from each of the villages, in contrast to those from five villages without treated nets. Circumstantial evidence indicates that bedbug resistance to pyrethroid insecticides may evolve more readily in villages with incomplete coverage rates of treated bednets, allowing bedbug infestations to become re‐established. Bedbugs have not returned to a village where nearly all the beds have been provided with pyrethroid‐treated bednets for 14 years.
A prospective randomized trial of an urban general practice attachment for medical students
Authors: Wade V , Silagy C , Mahoney S
Published: March 2003

A randomized controlled trial was undertaken to evaluate the effectiveness of a new model for providing urban general practice attachments for final‐year medical students at the Flinders University of South Australia. All the student groups in that year were randomized prospectively to either the standard student attachment, as run by the university, or to an attachment organized by a project team from a local network of general practitioners. Students in the intervention group had their personal learning goals assessed and matched with their general practice preceptors, and the students were set a task that developed their contact with other health resources in the community. Results from an evaluation questionnaire completed by the students at the end of their terms showed that the students in the intervention group rated their general practice preceptors more highly, had more contact with allied health and community organizations, felt that they had met their own learning goals to a greater extent, and enjoyed their term more. Student examination results showed that the students in the intervention group did not perform as well in one of the four areas of their end of term examination as did the students in the standard attachment. The additional cost of providing the intervention was estimated to be A$340 per student. We conclude that long‐term decisions about adopting this new model of organizing general practice attachments on a wider scale will need to balance the apparent benefits against the increased resources required.
The rise and fall of students' skill in obtaining a medical history
Authors: Pfeiffer C. , Madray H. , Ardolino A. , Willms J.
Published: March 2003

A gradual shift towards a more humanistic conception of medicine has occurred in recent years. Along with this shift have come attempts by medical educators to include interviewing and communication skills as part of the medical curriculum. The current study evaluates the effectiveness of a clinical medicine curriculum which emphasizes interviewing skills. Between 1992 and 1994 the 292 graduates of the University of Connecticut School of Medicine participated in five clinical skills teaching and assessment programmes during the four years of medical school. During each of these five programmes, the students' interviewing skills were rated using the Arizona Clinical Interview Rating Scale (ACIR). The raters were standardized patients with whom they had just completed a medical encounter. Results show that students' development of skills differed, with closure items showing the greatest increase and social history items showing the greatest decline, with an overall initial increase and then a decline in interviewing skills over the four years. Explanations for these findings include the de‐emphasis of communication skills during the clinical years and the culture of medicine to which students are exposed during these years.
Tutor intervention profile: reliability and validity
Authors: Grave Willem S De , Dolmans Diana H J M , Vleuten Cees P M van der
Published: March 2003

An instrument has been developed to provide tutors with feedback about their performance in problem‐based tutorial groups. This questionnaire consists of 33 statements reflecting the behaviour of the tutor in the tutorial group when students analyse the case and generate learning issues and the behaviour of the tutor when students report back to the tutorial group about their self‐study. The statements are grouped on theoretical dimensions found in the literature about co‐operative learning and problem‐based learning. This study focuses on the validity and the reliability of this instrument. Confirmatory factor analysis showed that a four‐factor model showed a weak fit, whereas each separate factor fitted the data reasonably well. The four factors are: (1) elaboration; (2) directing the learning process; (3) integration of knowledge and (4) stimulating interaction and individual accountability. These factors were strongly correlated with the overall judgement of the tutor at the end of the unit, so the concurrent validity of this instrument was high. Generalizability studies indicated that the rating scales provide reliable information with a sample size of student responses falling within the range of real tutorial group sizes. The results of this study show that the instrument for providing tutors with feedback is valid and reliable. This questionnaire can be used in staff development activities and also provides needs assessment for faculty development.
Informed consent in clinical training – patient experiences and motives for participating
Authors: Lynöe  , Sandlund  , Westberg  , Duchek
Published: March 2003

The purpose of this study was to assess patients' attitudes to and experiences of participating in the clinical training of medical students. Samples of patients (n = 582) selected at random from six different departments (gynaecology, psychiatry, internal medicine, paediatrics, urology and a health care centre with general practitioners) were interviewed by means of a questionnaire. The patients were selected from those who had consulted the actual departments in the last six months of 1995. Four hundred and forty‐one patients (76%) answered the questionnaire. Seventy‐one per cent of all patients had experience of participating; of these 41% had estimated that they had once or several times participated without being informed. Eighty per cent felt aggrieved if they were not informed. On average 88% were, in principle, positive to participating. Of those who were, in principle, negative a majority had negative experiences of participating. Elderly patients tended to accept participating more often without being informed. Almost all patients seemed to be positive to participating in the education of medical students, although a silent precondition might be that patients should be informed and given the opportunity to abstain.
Undergraduate surgical examinations: an appraisal of the clinical orals
Authors: Hardy  , Demos  , McNeil
Published: March 2003

The aims of this study of examinations in the final year of undergraduate surgery were to determine whether the long case, short cases/orals reflected students' knowledge of surgery effectively, whether their performance indicated the goals of the medical course relative to surgery were achieved, and whether these examinations gave a good and fair appraisal of student clinical skills. To test validity of these examinations, the scores of the long and short cases/oral were correlated with the aggregate score for the medical course, to the final‐year total score, the final‐year surgery mark, the written examination mark and the final‐year internal medicine mark. Whether the surgical goals of the medical course were achieved was assessed by questionnaire to the surgical examiners, and whether there was a good and relevant appraisal of student clinical skills was assessed by questionnaire to students. The response rates to the questionnaires were 100% and 98%. The results showed a poor but significant correlation between long and short cases/oral (rho = 0·24, P = 0·01). The correlation of the long case and short cases/oral to internal medicine was rho = 0·45 and rho = 0·33 (both P < 0·001), and there was a better correlation of short cases/oral to the aggregate medical course score (rho = 0·53 vs. 0·42, both P < 0·001). The long case and short cases/oral had no correlation with the written paper (rho = 0·10 and 0·69, respectively). The goals of the medical course were considered achieved, but less so with assessment of the injured and acutely surgically ill; students considered the long and short cases/orals as a good and relevant appraisal of their clinical skills. The distribution of short cases marks shifted to the left, indicating lower scores for this part of the examination. In conclusion, this study has demonstrated that the long and short cases/orals tested different aspects of student's skills, and so reinforces the importance of retaining the short and long cases in undergraduate surgical examinations. It is suggested that a single long case may be insufficient to distinguish between adequate and inadequate performance.
Peer‐reviewed publication following presentation at a regional surgical meeting
Authors: Bowrey David J , Morris‐Stiff Gareth J , Clark Geoffrey W B , Carey P Declan , Mansel Robert E
Published: March 2003

Objectives

 The aim of the study was to investigate the proportion of publications arising from work presented at a regional surgical meeting.

Design

 A list of all presentations to the Welsh Surgical Society 1983–95 was compiled and a detailed search made of the Medline Database. The surgical topic of each presentation, the date of presentation, the date of publication and the journal of publication were recorded.

Setting

 University Hospital of Wales.

Results

 Four hundred and ninety‐six papers were presented to the society, of which 402 (81%) were by trainees. The most frequent topics of presentation were colorectal (15%), vascular (15%) and hepato–pancreatico–biliary (11%). Two hundred and thirty‐three papers (47%) have been published in peer‐reviewed journals. The most popular journals for publication were Annals of the Royal College of Surgeons of England (19%), British Journal of Surgery (16%) and Journal of the Royal College of Surgeons of Edinburgh (8%). The median time from presentation to publication was 17·0 months (interquartile range 10·0–27·5 months).

Conclusions

 Regional surgical meetings have an important role in the annual surgical calendar and they are the ideal initial setting for presentation by trainees.
Population structure of African buffalo inferred from mtDNA sequences and microsatellite loci: high variation but low differentiation
Authors: SIMONSEN BO T. , SIEGISMUND HANS R. , ARCTANDER PETER
Published: March 2003

The African buffalo (Syncerus caffer) is widespread throughout sub‐Saharan Africa and is found in most major vegetation types, wherever permanent sources of water are available, making it physically able to disperse through a wide range of habitats. Despite this, the buffalo has been assumed to be strongly philopatric and to form large aggregations that remain within separate home ranges with little interchange between units, but the level of differentiation within the species is unknown. Genetic differences between populations were assessed using mitochondrial DNA (control region) sequence data and analysis of variation at six microsatellite loci among 11 localities in eastern and southern Africa. High levels of genetic variability were found, suggesting that reported severe population bottlenecks due to outbreak of rinderpest during the last century did not strongly reduce the genetic variability within the species. The high level of genetic variation within the species was found to be evenly distributed among populations and only at the continental level were we able to consistently detect significant differentiation, contrasting with the assumed philopatric behaviour of the buffalo. Results of mtDNA and microsatellite data were found to be congruent, disagreeing with the alleged male‐biased dispersal. We propose that the observed pattern of the distribution of genetic variation between buffalo populations at the regional level can be caused by fragmentation of a previous panmictic population due to human activity, and at the continental level, reflects an effect of geographical distance between populations.
High genetic differentiation among remnant populations of the endangeredCaesalpinia echinataLam. (Leguminosae–Caesalpinioideae)
Authors: CARDOSO M. A. , PROVAN J. , POWELL W. , FERREIRA P. C. G. , DE OLIVEIRA D. E.
Published: March 2003

Forest fragments along the Atlantic coastland of Brazil have been highly impacted by extensive human activities for the last 400 years.Caesalpinia echinata(Leguminosae– Caesalpinioideae), brazilwood, was overexploited during this period due to its economical importance as a dye. As a result, the species has become endangered and today its total population size is very restricted. We have assessed the distribution of genetic variation between five natural populations of brazilwood by means of RAPD (random amplified polymorphic DNA) markers. Of the total genetic variability, 28.5% was attributable to differences between two geographical groups, 29.6% to population differences within groups and 42.0% to individual differences within populations. The high level of population differentiation observed is in contrast to that expected for a primarily outcrossed woody perennial plant, and suggests that there may be a degree of inbreeding. Our results are in agreement with previous studies which postulated thatC. echinatahas always occurred in clumps, being common in some places but rare in between. From a conservation point of view, different populations representing different regions should be protected and, yet, plants with different origins should not be synthesized into populations in a recovery process at the risk of loss and dilution of genetic information. This study demonstrates that RAPD markers were effective in establishing a clear correlation between genetic and geographical distance and in identifying areas of maximum diversity, and may be used as an initial approach to assess the partitioning of genetic variation in this endangered species.
Impact of wild‐type and genetically modifiedPseudomonas fluorescenson soil enzyme activities and microbial population structure in the rhizosphere of pea
Authors: NASEBY D. C. , LYNCH J. M.
Published: March 2003

The aim of this study was to determine the impact of wild‐type along with functionally and nonfunctionally modifiedPseudomonas fluorescensstrains in the rhizosphere. The wild‐type F113 strain carried a gene encoding the production of the antibiotic 2,4‐diacetylphloroglucinol (DAPG) useful in plant disease control, and was marked with alacZYgene cassette. The first modified strain was a functional modification of strain F113 with repressed production of DAPG, creating the DAPG‐negative strain F113 G22. The second paired comparison was a nonfunctional modification of wild‐type (unmarked) strain SBW25, constructed to carry marker genes only, creating strain SBW25 EeZY‐6KX. Significant perturbations were found in the indigenous bacterial population structure, with the F113 (DAPG+) strain causing a shift towards slower growing colonies (K strategists) compared with the nonantibiotic‐producing derivative (F113 G22) and the SBW25 strains. The DAPG+ strain also significantly reduced, in comparison with the other inocula, the totalPseudomonaspopulations but did not affect the total microbial populations. The survival of F113 and F113 G22 were an order of magnitude lower than the SBW 25 strains. The DAPG+ strain caused a significant decrease in the shoot‐to‐root ratio in comparison to the control and other inoculants, indicating plant stress. F113 increased soil alkaline phosphatase, phosphodiesterase and aryl sulphatase activities compared to the other inocula, which themselves reduced the same enzyme activities compared to the control. In contrast to this, the β‐glucosidase, β‐galactosidase andN‐acetyl glucosaminidase activities decreased with the inoculation of the DAPG+ strain. These results indicate that soil enzymes are sensitive to the impact of inoculation with genetically modified microorganisms (GMMs).
Variation between and within colonies in the termite: morphology, genomic DNA, and behaviour
Authors: HUSSENEDER C. , BRANDL R. , EPPLEN C. , EPPLEN J. T. , KAIB M.
Published: March 2003

We investigate the structure between and within colonies of Schedorhinotermes lamanianus (Isoptera: Rhinotermitidae) at a cluster of foraging galleries in Shimba Hills National Reserve, Kenya. Three independent methods (morphometrics of minor soldiers, multilocus fingerprinting from genomic DNA of workers, and aggression tests between workers) yielded concordant results concerning number and spatial extent of colonies as well as variation between and within colonies. At least three colonies exist in our study area. Genetic data reveal that the largest colony is genetically and spatially substructured in three subsidiary nests, which may form reproductive units. These subsidiary nests were not completely isolated as we were able to document exchange of workers. Subsidiary nests may facilitate foundation of colonies by budding which may generate isolation by distance (population viscosity).
Phylogeography of the West Indian manatee (Trichechus manatus): how many populations and how many taxa?
Authors: GARCIA‐RODRIGUEZ A. I. , BOWEN B. W. , DOMNING D. , MIGNUCCI‐GIANNONI A. A. , MARMONTEL M. , MONTOYA‐OSPINA R. A. , MORALES‐VELA B. , RUDIN M. , BONDE R. K. , McGUIRE P. M.
Published: March 2003

To resolve the population genetic structure and phylogeography of the West Indian manatee (Trichechus manatus), mitochondrial (mt) DNA control region sequences were compared among eight locations across the western Atlantic region. Fifteen haplotypes were identified among 86 individuals from Florida, Puerto Rico, the Dominican Republic, Mexico, Colombia, Venezuela, Guyana and Brazil. Despite the manatee’s ability to move thousands of kilometres along continental margins, strong population separations between most locations were demonstrated with significant haplotype frequency shifts. These findings are consistent with tagging studies which indicate that stretches of open water and unsuitable coastal habitats constitute substantial barriers to gene flow and colonization. Low levels of genetic diversity within Florida and Brazilian samples might be explained by recent colonization into high latitudes or bottleneck effects. Three distinctive mtDNA lineages were observed in an intraspecific phylogeny of T. manatus, corresponding approximately to: (i) Florida and the West Indies; (ii) the Gulf of Mexico to the Caribbean rivers of South America; and (iii) the northeast Atlantic coast of South America. These lineages, which are not concordant with previous subspecies designations, are separated by sequence divergence estimates of d = 0.04–0.07, approximately the same level of divergence observed between T. manatus and the Amazonian manatee (T. inunguis, n = 16). Three individuals from Guyana, identified as T. manatus, had mtDNA haplotypes which are affiliated with the endemic Amazon form T. inunguis. The three primary T. manatus lineages and the T. inunguis lineage may represent relatively deep phylogeographic partitions which have been bridged recently due to changes in habitat availability (after the Wisconsin glacial period, 10 000 BP), natural colonization, and human‐mediated transplantation.
Phylogeography of the freshwater fish, Mogurnda adspersa, in streams of northeastern Queensland, Australia: evidence for altered drainage patterns
Authors: HURWOOD D. A. , HUGHES J. M.
Published: March 2003

A phylogeographic survey was used to elucidate the relative roles of historical processes and contemporary gene flow in structuring the genetic pattern observed with Mogurnda adspersa. This species of freshwater fish is found in the rivers and streams of the northeastern highlands of Queensland, Australia. Specifically, this project focused on populations in the Tully and Herbert Rivers in the Atherton Tablelands. Sequence analysis indicated that three distinct clades exist in the headwaters of the Tully River. The population sampled from one of the Tully River streams (Cheetah Creek) contained haplotypes that displayed ≈ 3.4% sequence divergence from other haplotypes detected in this river. Furthermore, these haplotypes formed part of the clade which exists throughout not only the Herbert River but other surrounding drainages in the area. These results support the hypothesis that the current genetic structure is strongly affected by changes in drainage patterns due to geomorphological processes that occurred in the recent past.
Local genetic structure in red grouse (Lagopus lagopus scoticus): evidence from microsatellite DNA markers
Authors: PIERTNEY STUART B. , MACCOLL ANDREW D. C. , BACON PHILIP J. , DALLAS JOHN F.
Published: March 2003

Allelic variation at seven hypervariable tri‐ and tetranucleotide microsatellite loci was used to determine levels of population differentiation between 14 populations of red grouse (Lagopus lagopus scoticus) in northeast Scotland, UK. Despite the potential for long‐distance dispersal in grouse, and a semicontinuous habitat, significant population divergence was observed (mean RST = 0.153; P < 0.01) and an isolation‐by‐distance effect detected (Mantel test: P < 0.001). Examination of the spatial trend in principal component scores derived from allele frequencies among populations highlighted a barrier to gene flow that was confounding a simple isolation‐by‐distance effect. This barrier corresponded to an area of unsuitable habitat for grouse associated with a river system that bisected the study area. Mean genetic relatedness was higher for males than for females in all but one of the study populations, suggesting that the territorial behaviour and natal philopatry displayed by cocks have a manifold effect in generating the observed spatial genetic structure. Lower female relatedness values suggest a higher level of female‐mediated gene flow, which is sufficient to prevent the loss of genetic variation from within populations and the onset of inbreeding effects. The potential consequences of local subdivision for red grouse populations are discussed.
The distribution of random amplified polymorphic DNA (RAPD) diversity amongst populations of Isotoma petraea (Lobeliaceae)
Authors: Bussell
Published: March 2003

RAPDs were generated from plants of six populations of Isotoma petraea F. Muell. The species occurs on rock outcrops in southern and western Australia, with populations exhibiting different breeding systems, including complete autogamy, varying levels of outbreeding and complex hybridity. Non‐metric multidimensional scaling (nMDS) analysis of the random amplified polymorphic DNA (RAPD) data set clearly resolved all populations. The Pigeon Rock population, which is home to both complex hybrid and structural homozygote plants, was divided into those two groups by the nMDS analysis. There was little diversity in highly autogamous populations, but levels were higher in the outbred Yackeyackine population. All complex hybrid populations and plants possessed numerous genetic system‐specific RAPDs, some of which were shown to be held in fixed heterozygosity. Estimating GST using RAPDs has been problematical due to their dominance, and analytical methods usually rely on knowledge of the selfing rate or assume Hardy–Weinberg equilibrium. This assumption does not hold when populations exhibit fixed heterozygosity, and an alternative method, Shannon's Index, was used to partition genetic diversity. The distribution of genetic diversity fit expectations for an inbreeding species, with most of the variation (87.5%) occurring between populations. This compares to an average RAPD‐based GST of 59.6% for inbreeding species generally and 15.5% for outbreeding species.
Phylogeography of North American populations of the moss species Hylocomium splendens based on the nucleotide sequence of internal transcribed spacer 2 of nuclear ribosomal DNA
Authors: Chiang T. Y. , Schaal B. A.
Published: March 2003

Sequence variation of the internal transcribed sequence 2 (ITS2) region of nuclear ribosomal DNA (nrDNA) was investigated in 10 North American populations of Hylocomium splendens. Cladistic analyses supported the monophyly of this moss species, rooted at Hylocomiastrum and Neodolichomitra. Three geographically based groups (Great Lakes Forest, Appalachian Mountains, and Pacific Northwest) were identified by a minimum spanning network. Significant genetic differentiation was detected (FST = 0.197 − 0.390) among three geographical regions in North America. Although high genetic divergence exists within H. splendens, these results do not suggest sufficient divergence for designating sibling species.
Canonical correspondence analysis for estimating spatial and environmental effects on microsatellite gene diversity in brook charr (Salvelinus fontinalis)
Authors: Angers Bernard , Magnan Pierre , Plante Michel , Bernatchez Louis
Published: March 2003

The understanding of the relationships between environmental factors and evolutionary forces is of importance to preserve opportunities for the continuation of dynamic evolutionary and ecological processes. This involves the identification and quantification of the relative importance of environmental factors that may influence these processes. Nevertheless, environmental factors are generally interpreted in terms of hypothetical inferences as relationships between environmental and genetic variables are often difficult to quantify. In this study, we used a statistical framework based on canonical correspondence analysis in order to determine the relative contribution of drainage pattern and environmental factors in structuring inter‐ and intrapopulational genetic diversity among brook charr populations as depicted by microsatellite analysis. These procedures simultaneously analyse several sets of variables and determine their relative contribution. The results revealed the influence of drainage pattern, altitude and human‐induced factors on the pattern of genetic diversity and, particularly, the important role of historical events in explaining patterns of contemporary genetic diversity among populations. The statistical framework used in this study provides an efficient way to empirically relate variations of genetic diversity and descriptive variables in general.
Microsatellite and morphological analysis of population structure in the parthenogenetic freshwater snailMelanoides tuberculata: insights into the creation of clonal variability
Authors: Samadi S. , Mavárez J. , Pointier J.‐P. , Delay B. , Jarne P.
Published: March 2003

The distribution of variability was studied at various geographical scales in the tropical freshwater snailMelanoides tuberculata, in order to analyse the role of factors shaping this distribution, including the mating system and population dynamics. This parthenogenetic polyploid species reproduces mainly asexually, with males occurring at low frequency. About 800 individuals (38 sites) were sampled from Africa and the Middle East, where the species originated, and from recently colonized habitats in South and Central America, and especially the island of Martinique. We first described variation of general aspects and ornamentation of the shells. This analysis confirms the existence of discrete morphs. Second, individuals were studied at three microsatellite loci, showing that each morph is a genetic clone with some minor variation compatible with models of microsatellite evolution. The genetic analysis also showed much more variation within than between clones. However, two populations from Africa exhibited a large amount of variability, and a mixture of sexual and asexual reproduction might explain these genetic patterns. The worldwide distribution of variability is, therefore, compatible with the African origin of the species, and the introduction of a few clones in other parts of the world. These results also suggest that the distribution of variability in Martinique is influenced by flooding events, and that two morphs from Martinique can be interpreted as hybrids between two pre‐existing morphs, based on morphological, genetic and geographical arguments.
Microsatellites reveal clonal structure of populations of the thelytokous ant Platythyrea punctata (F. Smith) (Hymenoptera; Formicidae)
Authors: Schilder K. , Heinze J. , Gross R. , Hölldobler B.
Published: March 2003

Parthenogenesis is often thought to constitute an evolutionary dead end as compared with sexual reproduction because genetic recombination is limited or nonexistent in parthenogenetic populations. Yet there are many species to demonstrate that parthenogenesis can initially be extremely successful under certain environmental conditions. In this study we used microsatellite markers to investigate the genetic structure of four natural populations of the neotropical thelytokous parthenogenetic ant Platythyrea punctata. Ten dinucleotide microsatellites were isolated from a partial genomic library of P. punctata. Five of these were found to be polymorphic. In a subsequent analysis of 314 workers taken from 51 colonies, we detected low intraspecific levels of variation at all loci, expressed both in the number of alleles detected and heterozygosities observed. Surprisingly, we found almost no differentiation within populations. Populations rather had a clonal structure, with all individuals from all colonies usually sharing the same genotype. Only in one colony from Puerto Rico did some workers have an additional genotype. This low level of genotypic diversity probably reflects the predominance of thelytoky in P. punctata, together with genetic bottlenecks and founder effects. Cross‐species amplification of all 10 loci in 29 ant species comprising four different subfamilies yielded positive amplification products in only a limited number of species.
Intraspecific phylogeography ofLasmigona subviridis(Bivalvia: Unionidae): conservation implications of range discontinuity
Authors: King Tim L. , Eackles Michael S. , Gjetvaj Branimir , Hoeh Walter R.
Published: March 2003

A nucleotide sequence analysis of the first internal transcribed spacer region (ITS‐1) between the 5.8S and 18S ribosomal DNA genes (640 bp) and cytochromecoxidase subunit I (COI) of mitochondrial DNA (mtDNA) (576 bp) was conducted for the freshwater bivalveLasmigona subviridisand three congeners to determine the utility of these regions in identifying phylogeographic and phylogenetic structure. Sequence analysis of the ITS‐1 region indicated a zone of discontinuity in the genetic population structure between a group ofL. subviridispopulations inhabiting the Susquehanna and Potomac Rivers and more southern populations. Moreover, haplotype patterns resulting from variation in the COI region suggested an absence of gene exchange between tributaries within two different river drainages, as well as between adjacent rivers systems. The authors recommend that the northern and southern populations, which are reproductively isolated and constitute evolutionarily significant lineages, be managed as separate conservation units. Results from the COI region suggest that, in some cases, unionid relocations should be avoided between tributaries of the same drainage because these populations may have been reproductively isolated for thousands of generations. Therefore, unionid bivalves distributed among discontinuous habitats (e.g. Atlantic slope drainages) potentially should be considered evolutionarily distinct. The DNA sequence divergences observed in the nuclear and mtDNA regions among theLasmigonaspecies were congruent, although the level of divergence in the COI region was up to three times greater. The genusLasmigona, as represented by the four species surveyed in this study, may not be monophyletic.
Phylogeography of the California mountain kingsnake,Lampropeltis zonata(Colubridae)
Authors: Rodríguez‐Robles Javier A. , DeNardo Dale F. , Staub Richard E.
Published: March 2003

The phylogeography of the California mountain kingsnake,Lampropeltis zonata, was studied using mitochondrial DNA sequences from specimens belonging to the seven recognized subspecies and collected throughout the range of the species. Maximum parsimony and maximum likelihood methods identified a basal split withinL. zonatathat corresponds to southern and northern segments of its distribution. The southern clade is composed of populations from southern California (USA) and northern Baja California, Mexico. The northern clade is divided into two subclades, a ‘coastal’ subclade, consisting of populations from the central coast of California and the southern Sierra Nevada Mountains of eastern California, and a ‘northeastern’ subclade, mainly comprised of populations north of the San Francisco Bay and from the majority of the Sierra Nevada. We suggest that past inland seaways in southwestern California and the embayment of central California constituted barriers to gene flow that resulted in the two deepest divergences withinL. zonata. Throughout its evolutionary history, the northern clade apparently has undergone instances of range contraction, isolation, differentiation, and then expansion and secondary contact. Examination of colour pattern variation in 321 living and preserved specimens indicated that the two main colour pattern characters used to define the subspecies ofL. zonataare so variable that they cannot be reliably used to differentiate taxonomic units within this complex, which calls into question the recognition of seven geographical races of this snake.
Species relationships and population structure ofLittorina saxatilisOlivi andL. tenebrosaMontagu in Ireland using single‐strand conformational polymorphisms (SSCPs) of cytochromebfragments
Authors: Small M. P. , Gosling E. M.
Published: March 2003

Littorina saxatilisis a ubiquitous snail of intertidal habitats in the North Atlantic. Shell type in littorinids is extremely polymorphic and defined by habitat. Taxonomy based upon shell type has been revised in the light of anatomic and genetic information, but uncertainties remain. In this study, the population structure ofL. saxatilisandL. tenebrosawas studied at 11 sites in Ireland using single‐strand conformational polymorphisms of a 375‐bp portion of the cytochromebgene, and the status ofL. tenebrosa, the small, fragile‐shelled, brackish water type, was considered. The genetic patterns amongL. saxatilis andL. tenebrosapopulations were examined over varying distances andL. tenebrosawas compared with adjacentL. saxatilispopulations at four sites on the west coast of Ireland and one site on the east coast. Haplotype diversity was high with 32 haplotypes present among 995 individuals. Pairwise tests suggest gene flow over small scales among and between habitat types and may reflect the stochastic legacy of postglacial recolonization over larger scales. Inamovatests, geography explained nearly twice as much of the variance (30%) as habitat type (18%), indicating that gene flow is more restricted by distance than by habitat type, and supporting the status ofL. tenebrosaas an ecotype ofL. saxatilisrather than a separate species.
Mitochondrial DNA (mtDNA) reveals that female Bechstein’s bats live in closed societies
Authors: Kerth Gerald , Mayer Frieder , König Barbara
Published: March 2003

We present a microgeographic analysis of mitochondrial DNA (mtDNA) in Bechstein’s bats using three sources of control region sequence variability, including a novel mtDNA microsatellite, to assess individual relatedness both within and among 10 maternity colonies. Comparison of marker variability among 268 adult females revealed little genetic variability within each colony. However, most colonies were clearly distinguished by colony‐specific mitochondrial haplotypes (total n = 28). Low intracolony variability and strong haplotype segregation among colonies, was reflected by an extraordinary high FST of 0.68, indicating a very low intercolony dispersal rate of approximately one female in five generations. Haplotype distribution among 18 solitary males showed that males frequently disperse between colony locations, indicating the absence of dispersal barriers. Bechstein’s bat maternity colonies are thus closed groups that comprise 20–40 females probably belonging to only one or, at most, two matrilines. The genetic population structure of Bechstein’s bats is in agreement with the hypothesis that females seek familiar and, at least, partially related cooperation partners for raising their young. Alternatively strong philopatry might reflect the importance of profound roost or habitat knowledge for successful reproduction in female Bechstein’s bats.
Population structure of long‐finned pilot whales in the North Atlantic: a correlation with sea surface temperature?
Authors: Fullard K. J. , Early G. , Heide‐Jørgensen M. P. , Bloch D. , Rosing‐Asvid A. , Amos W.
Published: March 2003

The long‐finned pilot whale,Globicephala melas, is a social, pelagic odontocete distributed widely in the cold temperate waters of the North Atlantic. Despite genetic, morphometric, physiological and observational studies, it remains unclear whether any population substructure exists. We have used eight highly polymorphic microsatellite loci to analyse samples from four disparate sampling sites: USA East Coast (Cape Cod), West Greenland, the Faeroe Islands and the UK. Our results indicate that substructure does exist, and is particularly pronounced between West Greenland and other sites. The magnitudes of the various pairwise comparisons do not support a simple isolation‐by‐distance model. Instead, the patterns of genetic differentiation suggest that population isolation occurs between areas of the ocean which differ in sea surface temperature. Such a mechanism is supported by the observation that temperature is a primary factor determining the relative distributions of two short‐finned pilot whale (G. macrorhynchus) populations off the Pacific coast of Japan.
Examination of species boundaries in theAcropora cervicornisgroup (Scleractinia, Cnidaria) using nuclear DNA sequence analyses
Authors: Oppen M. J. H. Van , Willis B. L. , Vugt H. W. J. A. Van , Miller D. J.
Published: March 2003

AlthoughAcroporais the most species‐rich genus of the scleractinian (stony) corals, only three species occur in the Caribbean:A. cervicornis,A. palmataandA. prolifera. Based on overall coral morphology, abundance and distribution patterns, it has been suggested thatA. proliferamay be a hybrid betweenA. cervicornisandA. palmata. The species boundaries among these three morphospecies were examined using DNA sequence analyses of the nuclearPax‐C46/47 intron and the ribosomal DNA Internal Transcribed Spacer (ITS1 and ITS2) and 5.8S regions. Moderate levels of sequence variability were observed in the ITS and 5.8S sequences (up to 5.2% overall sequence difference), but variability within species was as large as between species and all three species carried similar sequences. Since this is unlikely to represent a shared ancestral polymorphism, the data suggest that introgressive hybridization occurs among the three species. For thePax‐Cintron,A. cervicornisandA. palmatahad very distinct allele frequencies andA. cervicorniscarried a unique allele at a frequency of 0.769 (although sequence differences between alleles were small). AllA. proliferacolonies examined were heterozygous for thePax‐Cintron, whereas heterozygosity was only 0.286 and 0.333 forA. cervicornisandA. palmata, respectively. These data support the hypothesis thatA. proliferais the product of hybridization between two species that have a different allelic composition for thePax‐Cintron, i.e.A. cervicornisandA. palmata. We therefore suggest thatA. proliferais a hybrid betweenA. cervicornisandA. palmata, which backcrosses with the parental species at low frequency.
The comparative phylogeography of Neotropical mammals: patterns of intraspecific mitochondrial DNA variation among bats contrasted to nonvolant small mammals
Authors: Ditchfield A. D.
Published: March 2003

The major aim of this study was to compare the phylogeographic patterns of codistributed bats and small nonvolant Neotropical mammals. Cytochrome b sequences (mitochondrial DNA) were obtained for a total of 275 bats representing 17 species. The tissue samples were collected in coastal Brazil, and were available from Mexico and the Guyana. The study concentrates on four species (Artibeus lituratus, Carollia perspicillata, Sturnira lilium and Glossophaga soricina) which were well represented. The other 13 species were sequenced to test the generality of the patterns observed. In general, sequence divergence values within species were low, with most bat species presenting less than 4% average sequence divergence, and usually between 1 and 2.5%. Clades of highly similar haplotypes enjoyed broad distribution on a continental scale. These clades were not usually geographically structured, and at a given locality the number of haplotypes was high (8–10). As distance increased, some moderately divergent clades were found, although the levels of divergence were low. This suggests a geographical effect that varied depending on species and scale. Small nonvolant mammals almost invariably have high levels of sequence divergence (> 10%) for cytochrome b over much shorter distances (< 1000 km). The grain of intraspecific variation found in small nonvolant mammals is much finer than in bats. Low levels of geographical structuring cannot be attributed to a slower evolutionary rate of bat DNA in relation to other mammalian taxa. The phylogeographic pattern of bats contrasts sharply with the pattern found for Neotropical rodents and marsupials.
Mitochondrial DNA phylogeography of Acrossocheilus paradoxus (Cyprinidae) in Taiwan
Authors: Wang J. P. , Hsu K. C. , Chiang T. Y.
Published: March 2003

Nucleotide sequences of 3′ end of the cytochrome b gene, tRNA genes, D‐loop control region, and the 5′ end of the 12S rRNA of mitochondrial DNA (mtDNA) were used to assess the genetic and phylogeographic structure of Acrossocheilus paradoxus populations, a Cyprinidae fish of Taiwan. A hierarchical examination of populations in 12 major streams from three geographical regions using an analysis of molecular variance (
amova) indicates high genetic differentiation both among populations (ΦST = 0.511, P < 0.001) and among regions (ΦCT = 0.368, P < 0.001). Limited migration largely contributed to the genetic differentiation. High nucleotide diversity (1.13%) and haplotype diversity (0.80%) were detected among populations. The degree of genetic differentiation was correlated with geographical distance between populations, a result consistent with the one‐dimensional stepping stone models. A neighbour‐joining tree recovered by (
dambe) supports the pattern of isolation by distance and reveals a closer relationship between populations of the central and southern regions. A minimum spanning network based on nucleotide substitutions reflected migration routes from populations of the central region to the northern and southern regions, respectively. Postglacial colonization and expansion can explain the phylogeographical pattern. Single and ancient migration events may have allowed the northern region to attain the monophyly of mtDNA alleles. In contrast, most populations within geographical regions are either paraphyletic or polyphyletic due to the relatively shorter time period for coalescence. Both low haplotype number and genetic variability suggest a bottleneck event in the Chingmei population of northern Taiwan. Based on coalescence theory, the monophyly of the Tungkang population of the southern region may be associated with a founder event.