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Strong Differentiation (strong + differentiation)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Life history and population size variability in a relict plant.

DIVERSITY AND DISTRIBUTIONS, Issue 1 2008
Different routes towards long-term persistence
ABSTRACT A central tenet of conservation biology is that population size affects the persistence of populations. However, many narrow endemic species combine small population ranges and sizes with long persistence, thereby challenging this tenet. I examined the performance of three different-sized populations of Petrocoptis pseudoviscosa (Caryophyllaceae), a palaeoendemic rupicolous herb distributed along a small valley in the Spanish Pyrenees. Reproductive and demographic parameters were recorded over 6 years, and deterministic and stochastic matrix models were constructed to explore population dynamics and extinction risk. Populations differed greatly in structure, fecundity, recruitment, survival rate, and life span. Strong differentiation in life-history parameters and their temporal variability resulted in differential population vulnerability under current conditions and simulated global changes such as habitat fragmentation or higher climatic fluctuations. This study provides insights into the capacity of narrow endemics to survive both at extreme environmental conditions and at small population sizes. When dealing with species conservation, the population size,extinction risk relationship may be too simplistic for ancient, ecologically restricted organisms, and some knowledge of life history may be most important to assess their future. [source]

SINE insertion polymorphism on the X chromosome differentiates Anopheles gambiae molecular forms

INSECT MOLECULAR BIOLOGY, Issue 4 2005
M. J. Barnes
Abstract Polymorphic SINE insertions can be useful markers for assessing population structure and differentiation. Maque is a family of SINE elements which, based on bioinformatic analysis, was suggested to have been active recently in Anopheles gambiae, the major vector of malaria. Here, we report the development of polymorphic Maque insertions as population genetic markers in A. gambiae, and the use of these markers to better characterize divergence on the X chromosome between A. gambiae M and S molecular forms in populations from Burkina Faso and Mali. Our data are consistent with the recent activity of Maque. Phylogenetic analysis suggests that at least two recently active lineages may have a role in mediating genome evolution. We found differences in element insertion frequency and sequence between the M and S populations analysed. Significant differentiation was observed between these two groups across a 6 Mb region at the proximal (centromeric) end of the X chromosome. Locus-specific FST values ranged from 0.14 to 1.00 in this region, yet were not significantly different from zero in more distal locations on the X chromosome; the trend was consistent in populations from both geographical locales suggesting that differentiation is not due to local adaptation. Strong differentiation between M and S at the proximal end of the X chromosome, but not outside this region, suggests the action of selection counteracting limited gene flow between these taxa and supports their characterization as incipient species. [source]

LIBERALIZATION OF EUROPEAN TELECOMMUNICATIONS: SECTORAL DYNAMICS AND STRUCTURAL MUTATIONS

ANNALS OF PUBLIC AND COOPERATIVE ECONOMICS, Issue 3 2007
Philippe BANCE
ABSTRACT,:,This contribution intends to draw up an assessment of structural changes in the telecommunications sector impelled by the European policy of liberalization. Deep transformations with contrasted results have occurred. A strong differentiation in offer of services and a considerable fall in cost appears. After a strong growth, however, investment sharply decreased with the financial crisis. Employment has become a variable of adjustment for companies subjected to strong risks due to the economic situation. Lastly, the assertion of the universal service of telecommunications is accompanied by an important reduction of public service missions. [source]

Genetic differentiation among the Maculinea species (Lepidoptera: Lycaenidae) in eastern Central Europe

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2007
KATALIN PECSENYE
The present study aimed to analyse the level of genetic variation in the eastern Central European (Slovenia, Hungary, and Romania/Transylvania) populations of the Large Blues (Maculinea) to analyse the pattern of differentiation both between and within the species. One objective was to compare the level of differentiation between the two disputed species (Maculinea alcon and Maculinea rebeli) with that among the other species. Imagos were collected from 23 localities in eastern Central Europe in 2002. Enzyme polymorphism was analysed using polyacrylamide gel electrophoresis. Fourteen enzyme loci were studied in all samples. In the analysis of the data, F -statistics and Nei's genetic distances were calculated and a dendrogram (unweighted pair group method with arithmetic mean) was constructed on the basis of the distance matrix. A multivariate analysis of variance was performed to study the pattern of genetic differentiation among the samples. Principal component analysis analysis was also carried out using the allele frequency data of the samples. Our results indicated that the large blues are generally less polymorphic than other European lycaenid butterflies studied. At the same time, the level of genetic differentiation was high, even among local populations within the species. A low level of genetic variation within the populations coupled with strong differentiation among them implies the effect of genetic drift. Strong genetic differentiation of four Maculinea species (M. alcon, Maculinea teleius, Maculinea nausithous, and Maculinea arion) was confirmed. Significant differentiation was not found between M. alcon and M. rebeli. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 11,21. [source]