Home About us Contact
|
Home About us Contact | ||
|
|
||
New Populations (new + population)
Selected AbstractsCommon variants in the ATP-sensitive K+ channel genes KCNJ11 (Kir6.2) and ABCC8 (SUR1) in relation to glucose intolerance: population-based studies and meta-analyses,DIABETIC MEDICINE, Issue 5 2005R. M. Van Dam Abstract Aims To evaluate the relation between common variants in the ATP-sensitive K+ channel genes and glucose intolerance. Methods We conducted a meta-analysis of reported association studies in Caucasian populations for common variants in the ABCC8 (exons 16 and 18) and the KCNJ11 (E23K) gene and examined sources of heterogeneity in the results. The meta-analysis was based on 7768,10216 subjects (depending on the gene variant), and included two new population-based studies in the Netherlands with 725 cases and 742 controls. Results For the KCNJ11 variant, the summary odds ratio (OR) for glucose intolerance was 1.12 (1.01,1.23, P = 0.03) for the EK genotype and 1.44 (1.17,1.78, P = 0.0007) for the KK genotype, as compared with the EE genotype. For the ABCC8 exon 16 variant, the OR was 1.06 (0.94,1.19, P = 0.34) for ct and 0.93 (0.71,1.20, P = 0.56) for tt, as compared with the cc genotype. For ABCC8 exon 18, the OR was 1.20 (0.97,1.49, P = 0.10) for CT/TT, as compared with the CC genotype. Studies of the ABCC8 variants that were published first or had smaller sample sizes (for the exon 18 variant) showed stronger associations, which may indicate publication bias. For the ABCC8 exon 18 and the KCNJ11 variant, associations were stronger for studies of clinical diabetes than newly detected glucose intolerance. The population attributable risk for clinical Type 2 diabetes was 6.2% for the KCNJ11 KK genotype and 10.1% for the KCNJ11 EK and KK genotype combined. Conclusions The common KCNJ11 E23K gene variant, but not the ABCC8 exon 16 or exon 18 variant, was consistently associated with Type 2 diabetes. [source] Fitness drift of an atrazine-degrading population under atrazine selection pressureENVIRONMENTAL MICROBIOLOGY, Issue 3 2008Marion Devers Summary Pseudomonas sp. ADP harbouring the atrazine catabolic plasmid ADP1 was subcultured in liquid medium containing atrazine as sole source of nitrogen. After approximately 320 generations, a new population evolved which replaced the initial population. This newly evolved population grew faster and degraded atrazine more rapidly than the initial population. Plasmid profiles and Southern blot analyses revealed that the evolved strain, unlike the ancestral strain, presented a tandem duplication of the atzB gene encoding the second enzyme of the atrazine catabolic pathway responsible for the transformation of hydroxyatrazine to N-isopropylammelide. This duplication resulted from a homologous recombination that occurred between two direct repeats of 6.2 kb flanking the atzB gene and constituted by the insertion sequences IS1071, ISPps1 and a pdhL homologous sequence. This study highlights the IS-mediated plasticity of atrazine-degrading potential and demonstrates that insertion sequences not only help to disperse the atrazine-degrading gene but also improve the fitness of the atrazine-degrading population. [source] Chronic hypothyroidism only marginally affects adult-type Leydig cell regeneration after EDS administrationINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 1 2010Eddy Rijntjes Summary Chronic prenatally induced dietary hypothyroidism delays adult-type Leydig cell development, but does not block this process. Using a chemical model to induce hypothyroidism, it was suggested that development of a new population of Leydig cells was completely inhibited following the addition of the cytotoxic compound ethane-1,2-dimethyl sulphonate (EDS). In this study, we used a dietary approach to induce hypothyroidism and reinvestigated the regeneration of the Leydig cell population following EDS administration. Eighty-four day old euthyroid and chronically hypothyroid rats received an injection of EDS and were killed directly before or at regular intervals up to 77 days after EDS. In some control and hypothyroid animals, the first progenitor-type Leydig cells were observed at day 12 after EDS. At day 16, Leydig cell progenitors were present in all rats. The percentage of proliferating Leydig cells peaked in the euthyroid animals at day 21 after EDS. In the hypothyroid testis such a peak was not observed, although the percentage of proliferating regenerating Leydig cells was significantly higher from days 35 to 56 compared with the controls. This suggested that the wave of Leydig cell proliferation was delayed in the hypothyroid animals as compared with the euthyroid controls. On the day of EDS injection, the Leydig/Sertoli cell ratio was 37% lower in the hypothyroid rats compared with the controls. The Leydig/Sertoli cell ratio remained lower in the EDS-treated hypothyroid animals compared with the controls at all time points investigated. At day 77 after EDS, the Leydig cell population had returned to its pre-treatment size in both groups. Plasma testosterone production was reduced to below detectable levels immediately after EDS injection, and started to increase again on day 16, reaching pre-treatment values on day 21 in both groups. Taken together, severely reduced thyroid hormone levels did not block the regeneration of the adult-type Leydig cell population following EDS, as has been suggested previously. [source] The European Male Ageing Study (EMAS): design, methods and recruitmentINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 1 2009David M. Lee Summary Life expectancy is increasing in most developed countries, in part due to improved socioeconomic conditions and in part to advances in healthcare. It is widely acknowledged that the promotion of healthy ageing by delaying, minimizing or preventing disabilities or diseases is one of the most important public health objectives in this century. In contrast to the menopausal transition in females, we know relatively little about the contribution of androgens and anabolic hormones to the quality of ageing in men. The European Male Ageing Study (EMAS) is a multicentre prospective cohort designed to examine the prevalence, incidence and geographical distribution of gender-specific and general symptoms of ageing in men, including their endocrine, genetic and psychosocial predictors. Men aged 40,79 years were recruited from eight European centres: Florence (Italy), Leuven (Belgium), Lodz (Poland), Malmö (Sweden), Manchester (UK), Santiago de Compostela (Spain), Szeged (Hungary) and Tartu (Estonia). Subjects were recruited from population registers and those who agreed to take part completed a detailed questionnaire including aspects of personal and medical history, lifestyle factors and sexual function. Objective measures of body size, cognition, vision, skeletal health and neuromuscular function were obtained. Blood and DNA specimens were collected for a range of biochemical and genetic analyses. After an average of 4 years, it is planned to resurvey the participants with similar assessments. A total of 3369 men with a mean age of 60 ± 11 years were recruited. The mean centre response rate was 43%, and highest in those aged 50,59 years. Those who participated were marginally younger than those who were invited but declined to participate (60.0 vs. 61.1 years). Participants left education slightly later than a sample of non-participants, though there were no consistent differences in levels of general health, physical activity, or smoking. EMAS will provide new population-based data concerning the main features that characterize ageing in men and its critical determinants, particularly with reference to age-related changes in hormone levels. Such information is an important prerequisite to develop effective strategies to reduce age-related disabilities and optimise health and well-being into old-age. [source] End-to-end QoS and global mobility management in an integrated satellite/terrestrial networkINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2004P. Conforto Abstract For decades, the development of the Internet was driven by the purpose of providing applications to non-mobile users. No specific Quality of Service (QoS) requirement is necessary, other than ensuring reliability in the end-to-end data transfers. As such, best effort service model was deemed more than appropriate to satisfy the users' needs. Nevertheless, the scenario has changed in the last few years. A new population of nomadic users, who requires access to Internet services regardless of their location and mode of transportation is growing, while new typologies of Internet applications are being continuously developed, in which best effort service level may no longer be adequate. The SUITED project has been devised to address the emerging issues generated by this new and challenging scenario. SUITED aims at contributing towards the design and deployment of the Global Mobile Broadband System (GMBS), a unique satellite/terrestrial infrastructure, which will ensure that nomadic users have access to Internet services with a negotiated QoS. An overview of the main results achieved in the SUITED project is provided in this article. Some of the most innovative solutions developed by the SUITED team for the joint management of global mobility and end-to-end QoS support are presented. The SUITED demonstrator platform, which was developed to validate the system specifications, is also described. Finally, the results of the experimental measurement campaigns carried out with this platform are reported. Copyright © 2004 John Wiley & Sons, Ltd. [source] Adaptation to the laboratory environment in Drosophila subobscuraJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2000Matos Adaptation to a novel environment is expected to have a number of features. Among these is a temporal increase in fitness and some or all of its components. It is also expected that additive genetic variances for these fitness characters will fall. Finally, it is expected that at least some additive genetic correlations will decrease, from positive toward negative values. In a study of several life-history variables in a Drosophila subobscura population sampled from the wild and then cultured in the laboratory, we did not find any such longitudinal trends over the first 29 generations. However, a temporal comparison (over 14 generations) of the later generations of this laboratory-adapted population with a new population, derived from a more recent wild-caught sample, indicated clearly that laboratory adaptation was nonetheless occurring. This study suggests the need for extensive replication and control in studies of the features of adaptation to a novel environment. [source] The genetics of adaptation to novel environments: selection on germination timing in Arabidopsis thalianaMOLECULAR ECOLOGY, Issue 7 2010BROOK T. MOYERS When studying selection during adaptation to novel environments, researchers have often paid little attention to an organism's earliest developmental stages. Despite this lack of attention, early life history traits may be under strong selection during colonization, as the expression of adaptive phenotypes at later points is contingent upon early survival. Moreover, the timing of early developmental transitions can constrain the timing of later transitions, with potentially large effects on fitness. In this issue, Huang et al. (2010) underscore the importance of early life history traits in the adaptation of Arabidopsis thaliana to old-field sites in North America. Using a new population of mapped recombinant inbred lines, the authors examined germination timing and total lifetime fitness of A. thaliana while varying site latitude, dispersal season, and maternal photoperiod. Huang et al. (2010) discovered several Quantitative Trait Loci (QTL) with large effects on fitness that colocalized with QTL for field germination timing and seed dormancy,demonstrating that fitness is genetically associated with these early life history traits, and that these loci are likely under strong selection during adaptation to novel environments. In the epistatic interactions of some loci, recombinant genotypes outperformed parental genotypes, supporting the potentially adaptive role of recombination. This study provides elegant evidence that traits expressed early in an organism's development can play an important role during adaptive evolution. [source] Population changes in Phytophthora infestans in Taiwan associated with the appearance of resistance to metalaxyl,PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 9 2002Kenneth L Deahl Abstract In recent years, late blight, caused by Phytophthora infestans (Mont) De Bary, has increased in severity in many parts of the world, and this has been associated with migrations which have introduced new, arguably more aggressive, populations of the pathogen. In Taiwan, late blight has been endemic on outdoor tomato crops grown in the highlands since the early 1900s, but recent epidemics have been more damaging. To ascertain the present status of the Taiwanese population of P infestans, 139 isolates of the pathogen collected and maintained by the Asian Vegetable Research and Development Center (AVRDC) were characterized using mating type, metalaxyl sensitivity, allozyme genotype, mitochondrial haplotype and RFLP fingerprinting. Up to 1997, all isolates were found to belong to the old clonal lineage of P infestans (US-1 and variants), but in isolates from 1998 a new genotype appeared, and by 2000 this had apparently completely displaced the old population. This new genotype was an A1 mating type and has the dilocus allozyme genotype 100/100/111, 100/100 for the loci coding for glucose-6-phosphate isomerase and peptidase, respectively. These characters, together with RG57 fingerprinting, indicated that these isolates belonged to the US-11 clonal lineage, a minority (11%) being a previously unreported variant of US-11. Whereas metalaxyl-resistant isolates were not detected in the old population, 96% of the new genotypes proved resistant, with the remainder being intermediate in sensitivity. It may be inferred from this sudden, marked change in the characteristics of the Taiwanese P infestans that a new population of the pathogen was introduced around 1997,98 and that this may well have already been metalaxyl-resistant when it arrived, although a role for in situ selection cannot be excluded. © 2002 Society of Chemical Industry [source] Establishment of a pharmacoepidemiological database in Germany: methodological potential, scientific value and practical limitationsPHARMACOEPIDEMIOLOGY AND DRUG SAFETY, Issue 3 2008Dipl., Iris Pigeot Dr rer.nat. Abstract Purpose We present a new population-based pharmacoepidemiological (PE) database obtained from statutory health insurances (SHIs) that is able to generate signals, to monitor prescribed drugs and to describe drug utilisation. We discuss methodological features of the database and we assess to which degree this database reflects basic demographic characteristics and hospitalisation rates of the general population. Methods Files of three SHIs were linked with drug dispensation data from a pharmacies' electronic data processing centre on an individual basis using the unique subject identification number (ID) at a trusted third party centre. Plausibility checks and descriptive analyses were carried out. Results The database covers 3.6 million SHI-members, provides drug utilisation data and data on hospitalisations. SHI membership is fairly stable over time. Our data indicate marked differences in socio-demographic characteristics between SHIs. Hospital admission rates standardised for age vary between 0.164 and 0.229 per person year, which is in good agreement with official statistics (0.20). The age distribution shows good agreement for men and some underrepresentation for women above the age of 60 as compared to the general population. Conclusions Confounder information on medical conditions, concomitant medications and socio-demographic variables can be obtained from the database, while the assessment of confounders related to lifestyle requires supplementary data collection. The database allows for a population-based approach and reflects daily practice including off-label use of drugs. Independent recording of exposure and outcome data prevents reporting bias on medication or outcome. Legal conditions that allow continuous updating of the database need to be settled. Copyright © 2008 John Wiley & Sons, Ltd. [source] On the incidence,prevalence relation and length-biased samplingTHE CANADIAN JOURNAL OF STATISTICS, Issue 2 2009Vittorio Addona MSC 2000: Primary 62N99; secondary 62G99 Abstract For many diseases, logistic constraints render large incidence studies difficult to carry out. This becomes a drawback, particularly when a new study is needed each time the incidence rate is investigated in a new population. By carrying out a prevalent cohort study with follow-up it is possible to estimate the incidence rate if it is constant. The authors derive the maximum likelihood estimator (MLE) of the overall incidence rate, ,, as well as age-specific incidence rates, by exploiting the epidemiologic relationship, (prevalence odds),=,(incidence rate),×,(mean duration) (P/[1,,,P],=,,,×,µ). The authors establish the asymptotic distributions of the MLEs and provide approximate confidence intervals for the parameters. Moreover, the MLE of , is asymptotically most efficient and is the natural estimator obtained by substituting the marginal maximum likelihood estimators for P and µ into P/[1,,,P],=,,,×,µ. Following-up the subjects allows the authors to develop these widely applicable procedures. The authors apply their methods to data collected as part of the Canadian Study of Health and Ageing to estimate the incidence rate of dementia amongst elderly Canadians. The Canadian Journal of Statistics © 2009 Statistical Society of Canada Pour beaucoup de maladies, des contraintes de logistique rendent les grandes études de cohortes difficiles à effectuer. Ceci devient un inconvénient particulièrement lorsqu'une nouvelle étude est devenue nécessaire afin d'étudier le taux d'indicence d'une nouvelle population. En menant une étude de cohorte prévalente avec relance, il est possible d'estimer le taux d'incidence lorsqu'il est constant. Les auteurs obtiennent l'estimateur du maximum de vraisemblance (EMV) pour le taux d'incidence globale, ,, ainsi que ceux par âge en exploitant la relation épidémiologique, (cote de prévalence)=(taux d'incidence),×,(durée moyenne) (P/[1,,,P],=,,,×,µ). Les auteurs obtiennent aussi les distributions des EMV et ils donnent des intervalles de confiance asymptotiques pour les paramètres. De plus, l'EMV de , est asymptotiquement le plus efficace et il est un estimateur naturel obtenu en substituant les estimateurs du maximum de vraisemblance marginale de P et µ dans P/[1,,,P],=,,,×,µ. La relance des sujets permet aux auteurs de développer ces procédures largement applicables. Les auteurs appliquent leur méthode à des données provenant de l'étude canadienne sur la santé et le vieillissement afin d'estimer le taux d'incidence de la démence parmi les Canadiens âgés. La revue canadienne de statistique © 2009 Société statistique du Canada [source] Descriptions of Protospathidium serpens (Kahl, 1930) and P. fraterculum n. sp. (Ciliophora, Haptoria), Two Species Based on Different Resting Cyst MorphologyTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 4 2005KUIDONG XU Abstract. Protospathidium serpens (Kahl, 1930) is frequent in semiterrestrial and terrestrial habitats worldwide. Conventionally, all populations are considered as conspecific because they have very similar overall morphologies and morphometrics. We studied in detail not only the morphology of the vegetative cells but also the resting cysts using live observation, protargol impregnation, and scanning electron microscopy. These revealed a cryptic diversity and biogeographic pattern in details of the dorsal brush and cyst wall morphology. The cyst wall is spiny in the Austrian specimens, while smooth in the South African and Antarctic populations. Accordingly, P. serpens consists of at least two species: P. serpens (with spiny cyst wall) and P. fraterculum n. sp. (with smooth cyst wall); the latter is probably composed of two distinct taxa differing by the absence (South African)/presence (Antarctic) of a monokinetidal bristle tail in brush row 3, the number of dikinetids comprising brush row 1 (seven versus three), and the total number of brush dikinetids (29 versus 17). Protospathidium serpens is neotypified with the new population from Austria. The significance of resting cyst morphology is discussed with respect to alpha-taxonomy and overall ciliate diversity. [source] Probing dark matter, galaxies and the expansion history of the Universe with Ly, in absorption and emissionASTRONOMISCHE NACHRICHTEN, Issue 5 2010M.G. Haehnelt Abstract Ly, radiation is an important diagnostic tool in a wide range of astrophysical environments. I will first describe here how measurements of the matter power spectrum on small scales from Ly, forest data constrain the mass of dark matter particles. I then will report on an ambitious program of searching for very faint spatially extended Ly, emission at z , 3 which has led to the discovery of a new population of faint Ly, emitters which I will argue should be identified with the long searched for host galaxies of damped Ly, absorbers. Finally, I will discuss the possibility of measuring the redshift drift of Ly, absorption features and therefore the change of the expansion rate of the Universe in real time with the ultra-stable high-resolution spectrograph CODEX proposed for the E-ELT (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Introduction Strategies Put to the Test: Local Adaptation versus HeterosisCONSERVATION BIOLOGY, Issue 3 2004PHILIPPINE VERGEER exogamia; introducciones multi-fuente; introducciones uni-fuente; Succisa pratensis Abstract:,Plant biodiversity has declined seriously because of both habitat deterioration and habitat fragmentation. As a result, many species have been forced into small, fragmented, and isolated populations and are believed to suffer from higher extinction risks. Genetic reinforcement and the establishment of new populations are now widely used to prevent extinction. However, the genetic background of transplants may seriously affect the long-term success of these populations because increased genetic variation may reduce the risk of inbreeding or lead to better performance by restored heterozygosity levels (heterosis). Introduced transplants, however, may be poorly adapted to the new local conditions. We tested the initial success of alternative introduction strategies. We evaluated the potential for inbreeding, heterosis, and/or local adaptation after introduction of artificial populations of Succisa pratensis. We introduced individuals from local and distant artificial populations that were created from either small or large populations. We created the artificial populations with the same census population size but varying effective population sizes by adjusting the relatedness of individuals. We analyzed the demographic consequences of inbreeding, heterosis, and/or local adaptation of these artificial populations. Reduced performance after selfing was manifested by a reduction in seed production, seed weight, germination, and flowering percentage. Seed production, seed weight, flowering percentage, and number of flowerheads were negatively affected by small population size. Local adaptation increased biomass and flowering percentage for local individuals. Seed weight and seed production exhibited significant heterosis. Our results demonstrate that threatened populations can benefit from introduction and genetic reinforcement of individuals from related populations. Significant differences among the artificial populations for several measured performance components suggest that introduction or reinforcement is best achieved through material from a local population or, when unavailable, from several large populations. Resumen:,La biodiversidad de plantas ha declinado seriamente tanto por el deterioro como la fragmentación de hábitats. Como resultado, muchas especies han sido relegadas a poblaciones pequeñas, fragmentadas y aisladas cuyos riesgos de extinción se piensa que son mayores. El reforzamiento genético y el establecimiento de poblaciones nuevas se utilizan ampliamente en la actualidad para prevenir la extinción. Sin embargo, los antecedentes genéticos de transplantes pueden afectar seriamente el éxito de estas poblaciones a largo plazo debido a que el incremento en la variación genética puede reducir el riesgo de endogamia o puede conducir a un mejor rendimiento por lograr niveles de heterocigosidad restaurados (heterosis). No obstante, los trasplantes introducidos pueden adaptarse deficientemente a las nuevas condiciones locales. Probamos el éxito inicial de estrategias de introducción alternativas. Evaluamos el potencial de endogamia, heterosis y/o adaptación local después de la introducción de poblaciones artificiales de Succisa pratensis. Introdujimos individuos de poblaciones locales y de poblaciones artificiales distantes que fueron creadas a partir de poblaciones tanto pequeñas como grandes. Las poblaciones artificiales fueron creadas con el mismo tamaño poblacional censal pero variaron en tamaños poblacionales efectivos al ajustar la parentela de los individuos. Analizamos las consecuencias demográficas de la endogamia, heterosis y/o adaptación local de estas poblaciones artificiales. Después de la autofecundación se manifestó una reducción en el rendimiento por reducción en la producción y peso de semillas y en el porcentaje de germinación y floración. La producción y peso de semillas, el porcentaje de floración y el número de botones florales fueron afectados negativamente por el tamaño poblacional pequeño. La adaptación local incrementó la biomasa y el porcentaje de floración en individuos locales. El peso y producción de semillas mostró heterosis significativa. Nuestros resultados demuestran que las poblaciones amenazadas pueden beneficiarse de la introducción y del reforzamiento genético de individuos de poblaciones emparentadas. Las diferencias significativas entre las poblaciones artificiales en varios de los componentes de rendimiento medidos sugiere que la introducción o reforzamiento se logra mejor con material de una población local o, cuando no disponible, con material de varias poblaciones grandes. [source] Genetic Diversity and Tests of the Hybrid Origin of the Endangered Yellow LarkspurCONSERVATION BIOLOGY, Issue 6 2001Jason A. Koontz The total number of individuals in these two populations is estimated to be <100. We used allozyme and random amplified polymorphic DNA ( RAPD) markers to (1) assess levels and patterns of genetic diversity in one wild population and two cultivated populations and (2) test the hypothesis that D. luteum is of hybrid origin between D. decorum and D. nudicaule. These data will be used to aid in developing a management plan to conserve the species. The wild population maintains high levels of genetic diversity. Genetic data indicate that both cultivated populations, especially the north Sonoma population, have several allozymes and RAPD markers not found in the wild population and could be used to establish new populations of D. luteum or to enhance the diversity and size of the wild population. The allozyme data did not reveal any fixed differences between D. decorum and D. nudicaule, although allele frequencies of the putative parental populations differed. At these loci, D. luteum resembled D. nudicaule more than D. decorum . Many unique RAPD markers distinguish each of the three species. The diagnostic markers from populations of D. nudicaule and D. decorum were not additive in the putative hybrid, and these data indicate that D. luteum is not of recent hybrid origin. Conservation of the yellow larkspur should include strategies that use the cultivated populations of D. luteum, but hybridizing D. decorum and D. nudicaule to "recreate"D. luteum is not recommended. Resumen:Delphidium luteum ( Ranunculaceae), un delfinio en peligro de extinción, está restringido a dos poblaciones silvestres cerca de Bodega Bay, California. Se estima que el total de individuos en estas dos poblaciones es de <100. Utilizamos marcadores de alozimas y RAPD para (1) evaluar los niveles y patrones de diversidad genética en una población silvestre y dos poblaciones cultivadas y (2) probar la hipótesis de que D. luteum es de origen híbrido entre D. decorum y D. nudicaule. Estos datos serán utilizados para ayudar a desarrollar un plan de manejo para conservar la especie. La población silvestre mantiene altos niveles de diversidad genética. Los datos genéticos indican que ambas poblaciones cultivadas, especialmente en la población de Sonoma norte, tienen varias alozimas y marcadores RAPD que no se encuentran en poblaciones silvestres y podrían utilizarse para establecer nuevas poblaciones de D. luteum o reforzar la diversidad y tamaño de la población silvestre. Los datos de alozimas no revelaron diferencias fijas entre D. decorum y D. nudicaule, aunque las frecuencias alélicas de las poblaciones parentales putativas fueron diferentes. En estos loci, D. luteum fue más semejante a D. nudicaule que a D. decorum. Muchos marcadores RADP únicos distinguen a cada una de las tres especies. Los marcadores diagnóstico de poblaciones de D. decorum y D. nudicaule no fueron aditivos en el híbrido putativo, y estos datos indican que D. luteum no es de origen híbrido reciente. La conservación del delfinio amarillo debería incluir estrategias que usen las poblaciones cultivadas de D. luteum; sin embargo, no se recomienda la hibridación de D. decorum y D. nudicaule para "recrear" a D. luteum. [source] Dispersal characteristics of three odonate species in a patchy habitatECOGRAPHY, Issue 1 2003S. Angelibert Dispersal has a potentially profound effect on the dynamics of populations especially when a population occupies a patchy habitat. Ponds surrounded by terrestrial landscape are an example of patchy distribution of physical conditions and constitute "islands" for odonates. Few studies have focussed on dispersal in odonates. We have used the direct method of dispersal observing (capture-mark-recapture technique) in order to estimate the degree of linkage in three patchy populations of odonate localised on three ponds. We also examined the differences in dispersal ability within and among three species (Coenagrion puella, Coenagrion scitulum and Libellula depressa). The ponds were situated in southwest France on a limestone plateau. In this arid area, these ponds constitute the only surface water available and are relatively sparsely distributed. The size of the ponds ranged from 48 to 79 m2 and they were 200 and 775 m apart. We demonstrated that three factors influence the dispersal ability of these odonates. The first is represented by the abiotic factors and especially weather conditions. This determines the number of days that dispersal is possible. The second is interspecific differences. We showed that sensitivity to weather conditions, species size and species behaviour influence dispersal ability. The third factor is the intraspecific characteristics. We demonstrated that there are differences in dispersal ability according to sex and age. To conclude, we discuss the importance of pond management to maintain the existing odonate populations and to facilitate introduction of new populations in this region where little exchange occurs between ponds. [source] Factors affecting the survival of founding individuals in translocated New Zealand Saddlebacks Philesturnus carunculatusIBIS, Issue 4 2007SABRINA S. TAYLOR Successful founders of new populations may represent a non-random sample of potential founding individuals. Using a recent Saddleback Philesturnus carunculatus translocation as a natural experiment, we related morphology, parasite load and genetic variation of translocated individuals to subsequent survivorship to assess the traits of successful founders. We also included capture location and holding time in our models to account for variables particular to translocations. Generalized linear model results suggest that, in addition to capture location, poor body condition (males) and the presence of ectoparasites (females) significantly reduced survivorship. Despite recent claims in the literature, we found no evidence that genetic variation was associated with survivorship or parasite load. [source] Intraspecific genetic analysis of the summer tanager Piranga rubra: implications for species limits and conservationJOURNAL OF AVIAN BIOLOGY, Issue 1 2007Tiffany M. Shepherd The summer tanager Piranga rubra is a Neotropical migrant that has experienced noted declines in the southwestern United States caused by extensive habitat loss of native riparian woodlands. This species is composed of two morphologically and behaviorally distinct taxa that traditionally have been recognized as subspecies, each occupying unique habitats in the southern part of North America. Genetic analyses of intraspecific variation are important in studies of threatened or endangered species because they can indicate whether smaller management units exist below the species level and they also provide estimates of within population variability. Using a mitochondrial DNA marker, the intraspecific genetic variation of this species is explored to determine whether the morphologically and behaviorally distinct subspecies are also genetically unique. By using traditional phylogenetic methods and building haplotype networks, results from this study indicate that the subspecies represent two phylogenetic species and should be managed as separate units. In addition, the level of gene flow among geographically isolated populations of the western subspecies is explored using Nested Clade Phylogeographic Analysis and population genetic tests. These analyses show that populations are genetically diverse and that haplotypes are shared across populations. Newly colonized populations are as diverse as older populations. This suggests that as habitat degrades in traditional breeding areas of the summer tanager, if suitable habitat elsewhere becomes available for new populations, these new colonies should be genetically diverse. [source] Atlantic reef fish biogeography and evolutionJOURNAL OF BIOGEOGRAPHY, Issue 1 2008S. R. Floeter Abstract Aim, To understand why and when areas of endemism (provinces) of the tropical Atlantic Ocean were formed, how they relate to each other, and what processes have contributed to faunal enrichment. Location, Atlantic Ocean. Methods, The distributions of 2605 species of reef fishes were compiled for 25 areas of the Atlantic and southern Africa. Maximum-parsimony and distance analyses were employed to investigate biogeographical relationships among those areas. A collection of 26 phylogenies of various Atlantic reef fish taxa was used to assess patterns of origin and diversification relative to evolutionary scenarios based on spatio-temporal sequences of species splitting produced by geological and palaeoceanographic events. We present data on faunal (species and genera) richness, endemism patterns, diversity buildup (i.e. speciation processes), and evaluate the operation of the main biogeographical barriers and/or filters. Results, Phylogenetic (proportion of sister species) and distributional (number of shared species) patterns are generally concordant with recognized biogeographical provinces in the Atlantic. The highly uneven distribution of species in certain genera appears to be related to their origin, with highest species richness in areas with the greatest phylogenetic depth. Diversity buildup in Atlantic reef fishes involved (1) diversification within each province, (2) isolation as a result of biogeographical barriers, and (3) stochastic accretion by means of dispersal between provinces. The timing of divergence events is not concordant among taxonomic groups. The three soft (non-terrestrial) inter-regional barriers (mid-Atlantic, Amazon, and Benguela) clearly act as ,filters' by restricting dispersal but at the same time allowing occasional crossings that apparently lead to the establishment of new populations and species. Fluctuations in the effectiveness of the filters, combined with ecological differences among provinces, apparently provide a mechanism for much of the recent diversification of reef fishes in the Atlantic. Main conclusions, Our data set indicates that both historical events (e.g. Tethys closure) and relatively recent dispersal (with or without further speciation) have had a strong influence on Atlantic tropical marine biodiversity and have contributed to the biogeographical patterns we observe today; however, examples of the latter process outnumber those of the former. [source] Monitoring and management of the endangered Cape mountain zebra Equus zebra zebra in the Western Cape, South AfricaAFRICAN JOURNAL OF ECOLOGY, Issue 2 2008Rebecca K. Smith Abstract De Hoop Nature Reserve and a neighbouring conservancy contain the most genetically diverse subpopulation of the Endangered (IUCN) Cape mountain zebra (Equus zebra zebra Linnaeus 1758). Although vital for the long-term stability of the meta-population, the population had received limited monitoring post-1999. We summarize data obtained during a population monitoring programme established in 2005. Ninety-nine individuals were identified indicating a decline in annual population growth from 6.6% (1995,1999) to 4.5% (1999,2005). The population was male biased and the deficit of females is likely to have prevented additional breeding herd formation resulting in excess nonbreeding males. These animals are currently of limited reproductive value to the meta-population and may be contributing to the decline in reproductive potential at De Hoop by competing for limited resources. One solution may be to translocate ,excess' males to reinforce existing small populations or establish new populations with females from elsewhere provided that a minimum of 78 animals is maintained at De Hoop to limit genetic loss. Population monitoring and effective management strategies for the De Hoop population and the meta-population are vital to ensure the long-term survival of Cape mountain zebra and for the success of other species recovery programmes. Résumé De Hoop Nature Reserve et une aire de conservation voisine contiennent la sous-population la plus génétiquement variée du zèbre de montagne du Cap (Equus zebra zebra Linnaeus 1758), classé« en danger » par l'UICN. Bien que vitale pour la stabilitéà long terme de la métapopulation, cette population a été peu suivie depuis 1999. Nous avons résumé les données recueillies au cours d'un programme de monitoring de la population instauré en 2005. Quatre-vingt dix-neuf individus ont été identifiés, ce qui indique un déclin de la croissance annuelle de la population de 6,6% (1995,1999) à 4,5% (1999,2005). La population est biaisée en faveur des mâles, et c'est probablement le déficit en femelles qui a empêché la formation d'un troupeau reproducteur supplémentaire, qui a abouti à un excès de mâles nonreproducteurs. Ces animaux sont actuellement de peu de valeur de reproduction pour la métapopulation et pourraient contribuer au déclin du potentiel reproducteur à De Hoop par la compétition qu'ils représentent pour les ressources limitées.Une solution pourrait être de déplacer les mâles « en excès » pour renforcer les petites populations existantes ou pour en établir de nouvelles avec des femelles venues d'ailleurs, pour autant qu'un minimum de 78 animaux restent à De Hoop pour limiter l'appauvrissement génétique. Des stratégies pour le monitoring et la gestion efficace de la population de De Hoop sont vitales pour garantir la survie à long terme du zèbre de montagne du Cap et pour la réussite des programmes de restauration d'autres espèces. [source] Long-term changes in the chromosomal inversion polymorphism of Drosophila subobscura.JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 3 2004Abstract The chromosomal polymorphism of 13 European populations of Drosophila subobscura has been compared with that of the same populations collected 15,35 years ago. The chromosomal polymorphism of the old populations differs significantly from that of the new populations, mainly for chromosomes U and O. There is a very good agreement between the geographical space and the genetic space as shown by a graphical representation of the 26 statistical populations (13 old and 13 new) obtained by a principal coordinate analysis. This reflects both the existence of significant latitudinal clines for the frequencies of some chromosomal arrangements in the old and new samples and systematic changes that have taken place in these populations during the period that elapsed between the two surveys. An increase in the frequency of those arrangements typical of southern latitudes and a decrease for those common in northern latitudes is observed in all populations , Mediterranean, Atlantic and Central European. Furthermore, the genetic distances of the new populations to a southern population of reference have decreased in comparison with those of the old populations. These changes could be the result of climatic factors that are correlated with latitude. In particular, the assumption that global warming is responsible for all the changes observed appears rather likely. Whether these systematic changes of the chromosomal polymorphism are a consequence of local adaptations or have been produced by migration from the south remains an open question. Zusamennfassung Der gegenwärtige chromosomale Inversionspolymorphismus in 13 europäischen Populationen von Drosophila subobscura wurde mit dem Zustand in denselben Populationen verglichen, die vor 15 bis 35 Jahren untersucht worden waren. Der Chromosomenpolymorphismus der ,,alten'' Populationen unterscheidet sich signifikant von dem der ,,neuen'' Populationen, besonders für die Chromosomen U und O. Eine sehr gute Übereinstimmung zeigt sich zwischen der geographischen Komponente und der genetischen Komponente bei einer graphischen Darstellung der 26 Populationen (13 alte und 13 neue Populationen) durch eine Koordinatenanalyse. Das spiegelt beides wider, die Existenz von signifikanten breitenabhängigen Klinen in der Häufigkeit einiger chromosomaler Strukturtypen in den alten und den neuen Populationen, aber auch die systematischen Änderungen, die sich bei diesen Populationen im Laufe der Zeit zwischen den beiden Untersuchungen ereignet haben. Eine Zunahme in den Häufigkeiten jener Chromosomenstrukturen, die typisch für südliche Breiten sind, und eine Abnahme solcher Strukturen, die häufig in nördliche Breiten sind, konnte beobachtet werden - in den mediterranen, den atlantischen und den mitteleuropäischen Populationen in der gleichen Weise. Außerdem haben die genetischen Distanzen der neuen Populationen zu einer südlichen Referenzpopulation im Vergleich zu denen der alten Populationen abgenommen. Diese Veränderungen wurden vermutlich von klimatischen Faktoren bestimmt, die mit der geographischen Breite korreliert sind. Insbesonders erscheint die Annahme, daß die globale Erwärmung für die Veränderungen des Chromosomenpolymorphismus dafür verantwortlich ist, ziemlich wahrscheinlich. Ob diese systematischen Transformationen des Chromosomenpolymorphismus ein Konsequenz lokaler Anpassungen oder auf Migration aus dem Süden zurückzuführen sind, bleibt eine offene Frage. [source] Multiple introductions promote range expansion of the mollusc Cyclope neritea (Nassariidae) in France: evidence from mitochondrial sequence dataMOLECULAR ECOLOGY, Issue 6 2006B. SIMON-BOUHET Abstract Since the 1970s, the nassariid gastropod Cyclope neritea has been extending its range north along the French Atlantic coasts from the Iberian Peninsula. This may be due to natural spread because of the recent warming of the northeastern Atlantic. However, human-mediated introductions related to shellfish culture may also be a probable explanation for this sudden range expansion. To examine these two hypotheses, we carried out a comprehensive study based on mitochondrial gene sequences (cytochrome oxidase I) of the five recently colonized French bays as well as 14 populations located in the recognized native range of the species. From a total of 594 individuals, we observed 29 haplotypes to split into three divergent clades. In the native range, we observed a low molecular diversity, strong genetic structure and agreement between geography and gene genealogies. Along the French coasts, we observed the opposite: high genetic diversity and low genetic structure. Our results show that recurrent human-mediated introductions from several geographical areas in the native range may be a source for the French Atlantic populations. However, despite the low dispersal ability of C. neritea, the isolation-by-distance pattern in France suggested that this gastropod may have been present (although unnoticed) on the French Atlantic coasts before the 1970s. As C. neritea shows characteristics of a cryptogenic species, the classification of Atlantic populations as either native or introduced is not straightforward. Cryptogenic species should be studied further to determine the status of new populations close to their recognized native range. [source] Isolation and characterization of nine microsatellite markers for Brachypodium sylvaticum (Huds.) Beauv., a recently invasive grass species in OregonMOLECULAR ECOLOGY RESOURCES, Issue 6 2008ALISA P. RAMAKRISHNAN Abstract The patterns of genetic diversity caused by rapid range expansions following recent colonizations are best observed using highly polymorphic genetic markers. We characterized nine microsatellite markers for Brachypodium sylvaticum, a bunchgrass invasive in the Northwestern United States and native to Eurasia. Loci exhibited from two to 10 alleles, and generally had high FIS values. These loci will help identify sources of new populations in the region, and they will be useful for studying patterns of genetic diversity during rapid range expansions. [source] Can differences in autonomous selfing ability explain differences in range size among sister-taxa pairs of Collinsia (Plantaginaceae)?NEW PHYTOLOGIST, Issue 3 2009An extension of Baker's Law Summary ,,Species with greater selfing ability are predicted to be better adapted for colonizing new habitats (Baker's Law). Here, we tested an expansion of this hypothesis: that species proficient at autonomous selfing have larger range sizes than their less proficient sister taxa. We also tested competing hypotheses regarding seed production and niche breadth on range size. ,,Floral traits affecting the proficiency of autonomous selfing were measured and seed production was calculated for six sister-taxa pairs in the clade Collinsia. We tested for the hypothesized effects of these variables on elevational distribution and range size. ,,We found that species most proficient at selfing had significantly larger range sizes than their sister-taxa that were less proficient at selfing. Species proficient at autonomous selfing occupied a higher mean elevation than their sister taxa, but they did not differ in their total elevational range. Species with greater seed production did not have larger range sizes. ,,Our results extend Baker's Law, suggesting that species proficient at autonomous selfing are better adapted to establish new populations and thus can more readily expand their range. Autonomous selfing ability may play a vital role in explaining variance in range size among other species. [source] Reproductive challenges of a rare grass, Calamagrostis porteri subsp. insperata (Swallen) C. Greene: implications for habitat restorationAPPLIED VEGETATION SCIENCE, Issue 3 2009David J. Gibson Abstract Background: Habitat management for reproductively challenged rare species is a problem when there is insufficient knowledge of their autecology. This study investigated reproductive failure in the rare grass Calamagrostis porteri ssp. insperata (Swallen) C. Greene (Reed bentgrass). Does the management recommendation of high light stimulate clonal growth, flowering, and seed production? Location: Shawnee National Forest, IL, USA, and in a greenhouse and an experimental garden at Southern Illinois University, Carbondale, IL, USA. Methods: Clones obtained from the three known Illinois populations were grown in a glasshouse under experimental light and soil moisture treatments. After 3 years, plants from the high light treatment were planted outside in an experimental garden where the light treatments were maintained for two more years. In the field, vegetative and flowering tiller density, canopy cover, and associated biotic and abiotic variables including abundance of co-occurring plant species were monitored for 5 years. The overhead tree canopy was cleared over a portion of one population. Results: In the glasshouse, plants increased in size under high light and moist soil, and there were size differences among populations. Sixty-six per cent (20 of 30) of the genets flowered when planted outdoors under full sunlight but did not produce seed. In the field, flowering only occurred in Calamagrostis growing in the cleared area, but no seed were produced. The plants in the flowering population were smaller than plants in the other two populations. The herbaceous community associated with Calamagrostis in the open diverged from the communities remaining under the shade. Conclusions: This study highlights the difficulty of managing reproductively challenged rare species. Calamagrostis populations can be managed to enhance clonal growth, but establishment of new populations would require translocation of vegetative material as it is highly unlikely that seed can be obtained. [source] Prospects for management strategies of invasive crayfish populations with an emphasis on biological controlAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2010M. A. Freeman Abstract 1.The white-clawed crayfish, Austropotamobius pallipes (Lereboullet), is the only freshwater crayfish indigenous to Great Britain and Ireland. It has a widespread, though declining distribution in England and parts of Wales but does not occur naturally in Scotland. 2.The North American signal crayfish, Pacifastacus leniusculus (Dana), is not native to Europe and was introduced to Britain in the 1970s. The signal crayfish out-competes the native white-clawed crayfish as it is larger and more aggressive. It is also responsible for the introduction and spread of crayfish plague, which has devastated white-clawed crayfish populations in Europe. 3.Signal crayfish populations are causing significant changes to the equilibrium of native flora and fauna through increased grazing and predation pressures; they also contribute to habitat degradation through burrowing. 4.Manual removal of crayfish using traps and pond trials with biocides have met with moderate success in reducing crayfish numbers and containing populations. However, with new populations of signal crayfish being reported each year within the UK, there is now an urgent need to develop a strategy with which to eradicate or contain their spread. 5.Signal crayfish have populated many habitat types in the UK, each of which may require a different control strategy; hence no single strategy or universal solution is likely to be attainable. 6.Signal crayfish are susceptible to various biocides and microbial pathogens but significant scientific research will be required to develop safe biological control methods and integrated pest management (IPM) strategies to control these invasive organisms. Copyright © 2009 John Wiley & Sons, Ltd. [source] Population genetics of the black ant Formica lemani (Hymenoptera: Formicidae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009PERTTU SEPPÄ Colony kin structure and spatial population structure were studied in multiple populations of the ant Formica lemani, using allozymes and DNA microsatellites. Average genetic relatedness between nestmate workers varied little between populations (r = 0.51,0.76), indicating that the average colony kin structure was relatively simple. Worker genotypes could not be explained with a single breeding pair in all nests, however, and the distribution of relatedness estimates across nests was bimodal, suggesting that single- and multi-queen colonies co-occur. We studied spatial population structure in a successional boreal forest system, which is a mixture of different aged habitats. Newly clear-cut open habitat patches are quickly colonized by F. lemani, where it is able to persist for a limited number of generations. Newly-founded populations showed signs of a founder effect and spatial substructuring, whereas older populations were more homogenous. This suggests that new populations are founded by a limited number of colonizers arriving from more than one source. Genetic differentiation among local populations was minor, indicating strong migration between them. There were, however, indications of both isolation by distance and populations becoming more isolated as habitat patches grew older. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 247,258. [source] Migration and the Right to Social Security: Perceptions of Off-farm Migrants' Rights to Social Insurance in China's Jiangsu ProvinceCHINA AND WORLD ECONOMY, Issue 2 2007Ingrid Nielsen J08; J 61; J65 Abstract In 2001 China ratified the International Covenant on Economic, Social and Cultural Rights. By so doing the national government became legally bound, "to the maximum of its available resources", to achieve "progressively" full realization of the rights specified in the Covenant. Included amongst these entitlements is the "right of everyone to social security, including social insurance". This paper uses data from Jiangsu to examine the extent to which urbanites agree that previously disenfranchised migrants have the same right to social insurance as the urban population. Many urbanites fear that their existing entitlements to social protection will be diluted if social insurance coverage is extended to include new populations. Accordingly, state agencies and the media have sought to promote acceptance of a more positive view of migrant workers than has traditionally prevailed within towns and cities. We find that younger urban residents, urban residents who already have social insurance and urban residents working in the state-owned sector are more likely to agree that migrants have the same right to social insurance as the urban population. [source] Variation in populations of Phytophthora infestans in Finland and Norway: mating type, metalaxyl resistance and virulence phenotypePLANT PATHOLOGY, Issue 1 2000Hermansen Phytophthora infestans was isolated from potato leaves and tubers collected from different parts of Finland in 1990,96 and Norway in 1993,96. Isolates were assessed for mating type, resistance to metalaxyl and virulence phenotype. In Finland 15% of 200 isolates tested and in Norway 25% of 642 tested were A2 mating type. Differences in the A1/A2 ratio were evident among regions and A2 was not found in northern areas. In Finland the frequency of metalaxyl-resistant isolates, among 1834 tested, decreased from 59% in 1990,95 to 2% in 1996. In Norway 59% of 491 isolates tested were resistant to metalaxyl in 1996. Among 269 Finnish and 105 Norwegian isolates, all known virulence genes were found in both countries and race 1.3.4.7.10.11 was the most common (resistance gene R9 was not included in the differential set). Oospores were observed in potato leaves from three locations in the southern part of Norway. The implications of the ,new' populations in the Nordic countries are discussed. [source] | |||||||||||||||||||||||||||||||