115 research outputs found

    Genetic variability and population structure of eastern white pine in a two hectare stand, Durham, New Hampshire

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    The genetic structure of a two hectare stand of eastern white pine (Pinus strobus L.) was studied by relating foliar allozyme composition of individual trees to tree location and age. Using starch gel electrophoresis, the trees were found to have variants for six of the seven enzymes analyzed. Trees of similar age and with common allozymes were found in clusters, suggesting that genetic structure existed in the stand. The genetic structure may have originated during establishment of several seedlings from common parents when openings were created in the canopy. Knowing that a genetic structure, such as that observed in this study, may exist in natural forests is important to foresters who are concerned with maintaining current levels of genetic variability in those forests. Evaluation of sampling strategies revealed that at least 50 randomly sampled trees would be required to correctly estimate allele frequencies, the number of alleles per locus, and heterozygosity in this stand. Smaller samples were likely to yield incorrect estimates by chance. To estimate polymorphism, between 100 and 250 trees would be needed. Reliable detection of deviations from allelic frequencies expected under the Hardy-Weinberg equilibrium required 25 to 425 randomly chosen trees, depending on allozyme frequencies for the enzyme in question. Differences in estimates for larger samples compared to smaller ones were due mainly to detection of additional low frequency alleles in the larger samples. These results indicate that cost and labor can be saved by selecting approximately ten percent of trees in a stand such as the one used in this study to obtain estimates for the first three measures, but more extensive and costly samples must be taken when estimating polymorphism and testing for deviation from the Hardy-Weinberg Equilibrium

    From endogenous to exogenous pattern formation: Invasive plant species changes the spatial distribution of a native ant

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    Invasive species are a significant threat to global biodiversity, but our understanding of how invasive species impact native communities across space and time remains limited. Based on observations in an old field in Southeast Michigan spanning 35 years, our study documents significant impacts of habitat change, likely driven by the invasion of the shrub, Elaeagnus umbellata, on the nest distribution patterns and population demographics of a native ant species, Formica obscuripes. Landcover change in aerial photographs indicates that E. umbellata expanded aggressively, transforming a large proportion of the original open field into dense shrubland. By comparing the ant’s landcover preferences before and after the invasion, we demonstrate that this species experienced a significant unfavorable change in its foraging areas. We also find that shrub landcover significantly moderates aggression between nests, suggesting nests are more related where there is more E. umbellata. This may represent a shift in reproductive strategy from queen flights, reported in the past, to asexual nest budding. Our results suggest that E. umbellata may affect the spatial distribution of F. obscuripes by shifting the drivers of nest pattern formation from an endogenous process (queen flights), which led to a uniform pattern, to a process that is both endogenous (nest budding) and exogenous (loss of preferred habitat), resulting in a significantly different clustered pattern. The number and sizes of F. obscuripes nests in our study site are projected to decrease in the next 40 years, although further study of this population’s colony structures is needed to understand the extent of this decrease. Elaeagnus umbellata is a common invasive shrub, and similar impacts on native species might occur in its invasive range, or in areas with similar shrub invasions.Invasive species are a threat to global biodiversity, but our understanding of how they impact native communities across space and time remains limited. We compared the spatial distribution of a population of native ant Formica obscuripes in SE Michigan between 1980 and 2015, during which the invasive shrub Elaeagnus umbellata changed the dominant landcover from open field to shrubland. Analyses of ant habitat preference and aggressivity suggest that this landcover change caused the nest pattern formation process to shift from endogenous (reproductive queen flights) that led to a uniform pattern, to both endogenous (nest budding) and exogenous (loss of preferred habitat), resulting in a significantly different clustered pattern. Results of a stage‐structured model suggest that the ant population may be declining. Elaeagnus umbellata is a common invasive shrub, and similar impacts on native species might occur in its invasive range, or in areas with similar shrub invasions.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136690/1/gcb13671.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136690/2/gcb13671_am.pd

    Autobiographical memory retrieval and appraisal in social anxiety disorder

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    The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.brat.2018.06.008 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Individuals with social anxiety disorder (SADs; n = 41) and healthy controls (HCs; n = 40) were administered the Waterloo Images and Memories Interview, in which they described mental images that they tend to experience in both anxiety-provoking and non-anxiety-provoking social situations. Participants then recalled, in as much detail as possible, specific autobiographical memories of salient aversive and non-aversive social experiences that they believed led to the formation of these images. Audio-recorded memory narratives were transcribed and coded based on the procedure of the Autobiographical Interview, which provides a precise measure of the degree of episodic detail contained within each memory. Participants also rated the subjective properties of their recalled memories. Results revealed that participants across the two groups retrieved equivalent rates of both aversive and non-aversive social memories. However, SAD participants' memories of aversive events contained significantly more episodic detail than those of HCs, suggesting that they may be more highly accessible. Moreover, participants with SAD appraised their memories of aversive experiences as more distressing and intrusive than HCs, and perceived them as having a significantly greater influence on their self-perception. In contrast, no group differences were observed for memories of non-aversive events. Findings have the potential to shed new light on autobiographical memory in SAD, with implications for psychotherapeutic intervention.Canada Research Chairs ProgramSocial Sciences and Humanities Research Council of CanadaCanadian Institutes of Health Researc

    Identification of stable reference genes for quantitative PCR in koalas

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    To better understand host and immune response to diseases, gene expression studies require identification of reference genes with stable expression for accurate normalisation. This study describes the identification and testing of reference genes with stable expression profiles in koala lymph node tissues across two genetically distinct koala populations. From the 25 most stable genes identified in transcriptome analysis, 11 genes were selected for verification using reverse transcription quantitative PCR, in addition to the commonly used ACTB and GAPDH genes. The expression data were analysed using stable genes statistical software - geNorm, BestKeeper, NormFinder, the comparative ΔCt method and RefFinder. All 13 genes showed relative stability in expression in koala lymph node tissues, however Tmem97 and Hmg20a were identified as the most stable genes across the two koala populations

    Might Depression, Psychosocial Adversity, and Limited Social Assets Explain Vulnerability to and Resistance against Violent Radicalisation?

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    BACKGROUND: This study tests whether depression, psychosocial adversity, and limited social assets offer protection or suggest vulnerability to the process of radicalisation. METHODS: A population sample of 608 men and women of Pakistani or Bangladeshi origin, of Muslim heritage, and aged 18-45 were recruited by quota sampling. Radicalisation was measured by 16 questions asking about sympathies for violent protest and terrorism. Cluster analysis of the 16 items generated three groups: most sympathetic (or most vulnerable), most condemning (most resistant), and a large intermediary group that acted as a reference group. Associations were calculated with depression (PHQ9), anxiety (GAD7), poor health, and psychosocial adversity (adverse life events, perceived discrimination, unemployment). We also investigated protective factors such as the number social contacts, social capital (trust, satisfaction, feeling safe), political engagement and religiosity. RESULTS: Those showing the most sympathy for violent protest and terrorism were more likely to report depression (PHQ9 score of 5 or more; RR = 5.43, 1.35 to 21.84) and to report religion to be important (less often said religion was fairly rather than very important; RR = 0.08, 0.01 to 0.48). Resistance to radicalisation measured by condemnation of violent protest and terrorism was associated with larger number of social contacts (per contact: RR = 1.52, 1.26 to 1.83), less social capital (RR = 0.63, 0.50 to 0.80), unavailability for work due to housekeeping or disability (RR = 8.81, 1.06 to 37.46), and not being born in the UK (RR = 0.22, 0.08 to 0.65). CONCLUSIONS: Vulnerability to radicalisation is characterised by depression but resistance to radicalisation shows a different profile of health and psychosocial variables. The paradoxical role of social capital warrants further investigation

    Who wants to talk to terrorists?

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    Interviewing terrorists or former terrorists has become an increasingly popular research method in terrorism studies. What terrorists say can shed light on motivations, decision-making processes and operational details that without first-hand testimony could only be inferred. In this chapter, a selection of these studies is reviewed alongside a consideration of global trends in terrorism and developments in terrorism research

    Une migration déqualifiante ?

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