			Home About us Contact

Diversity Surveys (diversity + survey)

Distribution by Scientific Domains

Life Sciences	80%

Selected Abstracts

Immigrants working with co-ethnics: Who are they and how do they fare?

INTERNATIONAL MIGRATION, Issue 2 2009
Feng Hou
Participation in ethnic economies has been regarded as an alternative avenue of economic adaptation for immigrants and minorities in major immigrant-receiving countries. This study examines one important dimension of ethnic economies: co-ethnic concentration at the workplace. Using a large national representative sample from Statistics Canada's 2002 Ethnic Diversity Survey, this study addresses four questions: (1) what is the level of co-ethnic concentration at the workplace for Canada's minority groups? (2) How do workers who share the same ethnicity with most of their co-workers differ from other workers in socio-demographic characteristics? (3) Is higher level of co-ethnic concentration at the workplace associated with lower earnings? (4) Is higher level of co-ethnic concentration at the workplace associated with higher levels of life satisfaction? The results show that only a small proportion of immigrants and the Canadian-born work in ethnically homogeneous settings. In Canada's eight largest metropolitan areas about 10 per cent of non-British/French immigrants share a same ethnic origin with the majority of their co-workers. The level is as high as 20 per cent among Chinese immigrants and 18 per cent among Portuguese immigrants. Among Canadian-born minority groups, the level of co-ethnic workplace concentration is about half the level for immigrants. Immigrant workers in ethnically concentrated settings have much lower educational levels and proficiency in English/French. Immigrant men who work mostly with co-ethnics on average earn about 33 per cent less than workers with few or none co-ethnic coworkers. About two thirds of this gap is attributable to differences in demographic and job characteristics. Meanwhile, immigrant workers in ethnically homogenous settings are less likely to report low levels of life satisfaction than other immigrant workers. Among the Canadian-born, co-ethnic concentration is not consistently associated with earnings and life satisfaction. [source]

Dominance of a clonal green sulfur bacterial population in a stratified lake

FEMS MICROBIOLOGY ECOLOGY, Issue 1 2009
Lea H. Gregersen
Abstract For many years, the chemocline of the meromictic Lake Cadagno, Switzerland, was dominated by purple sulfur bacteria. However, following a major community shift in recent years, green sulfur bacteria (GSB) have come to dominate. We investigated this community by performing microbial diversity surveys using FISH cell counting and population multilocus sequence typing [clone library sequence analysis of the small subunit (SSU) rRNA locus and two loci involved in photosynthesis in GSB: fmoA and csmCA]. All bacterial populations clearly stratified according to water column chemistry. The GSB population peaked in the chemocline (c. 8 × 106 GSB cells mL,1) and constituted about 50% of all cells in the anoxic zones of the water column. At least 99.5% of these GSB cells had SSU rRNA, fmoA, and csmCA sequences essentially identical to that of the previously isolated and genome-sequenced GSB Chlorobium clathratiforme strain BU-1 (DSM 5477). This ribotype was not detected in Lake Cadagno before the bloom of GSB. These observations suggest that the C. clathratiforme population that has stabilized in Lake Cadagno is clonal. We speculate that such a clonal bloom could be caused by environmental disturbance, mutational adaptation, or invasion. [source]

Universal primers and PCR of gut contents to study marine invertebrate diets

MOLECULAR ECOLOGY, Issue 3 2005
L. E. BLANKENSHIP
Abstract Determining the diets of marine invertebrates by gut content analysis is problematic. Many consumed organisms become unrecognizable once partly digested, while those with hard remains (e.g. diatom skeletons) may bias the analysis. Here, we adapt DNA-based methods similar to those used for microbial diversity surveys as a novel approach to study the diets of macrophagous (the deep-sea amphipods Scopelocheirus schellenbergi and Eurythenes gryllus) and microphagous (the bivalve Lucinoma aequizonata) feeders in the deep sea. Polymerase chain reaction (PCR) in conjunction with ,universal' primers amplified portions of the mitochondrial cytochrome c oxidase I (COI) gene for animals ingested by S. schellenbergi and E. gryllus and the 18S rRNA gene for lesser eukaryotes ingested by L. aequizonata. Amplified sequences were combined with sequences from GenBank to construct phylogenetic trees of ingested organisms. Our analyses indicate that S. schellenbergi, E. gryllus and L. aequizonata diets are considerably more diverse than previously thought, casting new light on the foraging strategies of these species. Finally, we discuss the strengths and weaknesses of this technique and its potential applicability to diet analyses of other invertebrates. [source]

Sampling within the genome for measuring within-population diversity: trade-offs between markers

MOLECULAR ECOLOGY, Issue 7 2002
S. Mariette
Abstract Experimental results of diversity estimates in a set of populations often exhibit contradictory patterns when different marker systems are used. Using simulations we identified potential causes for these discrepancies. These investigations aimed also to detect whether different sampling strategies of markers within the genome resulted in different estimates of the diversity at the whole genome level. The simulations consisted in generating a set of populations undergoing various evolutionary scenarios which differed by population size, migration rate and heterogeneity of gene flow. Population diversity was then computed for the whole genome and for subsets of loci corresponding to different marker techniques. Rank correlation between the two measures of diversity were investigated under different scenarios. We showed that the heterogeneity of genetic diversity either between loci (genomic heterogeneity, GH) or among populations (population heterogeneity, PH) varied greatly according to the evolutionary scenario considered. Furthermore, GH and PH were major determinants of the level of rank correlation between estimates of genetic diversities obtained using different kinds of markers. We found a strong positive relationship between the level of the correlation and PH, whatever the marker system. It was also shown that, when GH values were constantly low during generations, a reduced number of microsatellites was enough to predict the diversity of the whole genome, whereas when GH increased, more loci were needed to predict the diversity and amplified fragment length polymorphism markers would be more recommended in this case. Finally the results are discussed to recommend strategies for gene diversity surveys. [source]

Nested core collections maximizing genetic diversity in Arabidopsis thaliana

THE PLANT JOURNAL, Issue 1 2004
Heather I. McKhann
Summary The successful exploitation of natural genetic diversity requires a basic knowledge of the extent of the variation present in a species. To study natural variation in Arabidopsis thaliana, we defined nested core collections maximizing the diversity present among a worldwide set of 265 accessions. The core collections were generated based on DNA sequence data from a limited number of fragments evenly distributed in the genome and were shown to successfully capture the molecular diversity in other loci as well as the morphological diversity. The core collections are available to the scientific community and thus provide an important resource for the study of genetic variation and its functional consequences in Arabidopsis. Moreover, this strategy can be used in other species to provide a rational framework for undertaking diversity surveys, including single nucleotide polymorphism (SNP) discovery and phenotyping, allowing the utilization of genetic variation for the study of complex traits. [source]