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HIGH GENE-FLOW BETWEEN DIANTHUS SYLVESTRIS POPULATIONS FROM SERPENTINE AND LIMESTONE SUGGESTS AN OLIGOGENIC NATURE OF LOCAL ADAPTATION
No full textLocal adaptation and gene flow are the two sides of the same coin: while gene flow tends to homogenize the allele
frequencies, decreasing the variability between populations, local adaptation acts selecting and promoting those
alleles better performing in each environment, thus increasing differences among populations. In the ecological
speciation, local adaptation has a central role in initiating population divergence as natural selection on traits that
confer ecological divergence could also produce, as a by-product, divergent selection on the traits that confer
reproductive isolation, such as, for instance, flowering time differences (1). However, although divergent selection
can favour reproductive isolation at a local scale, incipient divergence can be prevented by the homogenising
effect of gene flow between adjacent populations, maintaining species cohesion (2). Investigations into transient
stages in the continuum between local adaptation and incipient speciation are integral to speciation research.
Serpentine soils represent an excellent system for investigating the contribution of local adaptation to plant speciation
as indirectly testified by the striking levels of endemism and the distinctive flora they possess relative to
surrounding areas. The main characteristics of serpentine soils, defined “serpentine syndrome”, are low amounts
of calcium opposed to high amounts of magnesium, relatively high concentrations of nickel, chromium and other
heavy metals, and low water retention (3). Thus, adaptation to serpentine soils can contribute indirectly to pre- or
post-zygotic reproductive barriers that genetically isolate serpentine populations from non-serpentine relatives.
Additionally, the patchy distribution of serpentine soils can contribute to the geographic isolation of populations
by limiting the homogenizing effect of inter-population gene flow. Here we investigated the amount of gene-flow
and genetic divergence among populations of Dianthus sylvestris (Caryophyllaceae) occurring both on serpentine
outcrops and adjacent limestone sites in order to highlight if local adaptation enhanced the genetic divergence
among populations.
Plants from serpentine outcrops and calcareous soils were collected from populations of north-centre of Italy
and levels of population divergence and genetic connection were determined with molecular markers. Alleles of
10 microsatellites loci (SSR) derived from an EST library were characterized. All populations showed an high
percentage of polymorphic loci (ranging from 71% to 100%) and the distribution of allele frequencies showed
no significant differences among populations. Similarly allele richness was comparable among populations of
serpentine and limestone. The M-ratio approach ruled out that the populations, even if small in size, have been
subject to recent bottleneck, although the positive values of the inbreeding index (0.172<Fis<0.2894) suggest the
occurrence of crosses among related individuals. Both ANOVA (86% of the variability within populations, 14%
between populations) and the low values of differentiation among populations (mean Fst= 0.119, among populations)
confirmed the low overall genetic differentiation with the notable exception of a single population from
Val di Susa, which showed higher values of Fst (mean Fst = 0.3194, between Val di Susa and other populations).
In particular the locus DSL16 was found more strongly differentiated than expected by chance (Fst = 0.713,
p≤0.05), consistent with a scenario of divergent selection. Nevertheless this locus was not found as outlier in
any Fst estimation between serpentine and limestone populations. Bayesian (STRUCTURE) and multivariate approach
(PCoA) ruled out that populations of limestone and serpentine soils cluster in two genetically differentiated
groups and Mantel test did not identify a significant correlation with geographic distance. Thus, in contrast
with several previous studies, D. sylvestris does not show any evident genetic differentiation among populations
from serpentine and limestone. Instead, these likely behave as a meta-population, with the intensity of gene flow
apparently masking any potential effect of local adaptation. This suggests, for D. sylvestris, that adaptation to
serpentine soil may have an oligogenic basis, such as that local divergence in the few genes conferring adaptation
can be maintained in spite of extensive gene-flow among demes
Local adaptation and gene flow in serpentine and limestone populations of D. sylvestris
Full text linkPatchy distribution and stressful conditions of environment can induce the emergence of locally adapted phenotypes. Evolutionary theory supports that local adaptation is drown by strength of divergent selection to favor the genotype that better performs in a specific habitat. Nevertheless, adaptation could occur also via phenotypic plasticity that allows individuals to rapidly change their phenotypic response to environment and this ability may even slow down the effect of adaptive genetic divergence.
Plants from serpentine represent a typical model for studying local adaptation to soil type as selection in this environment is very intense and leads to the evolution of locally adapted populations, a phenomenon known as “serpentine syndrome”. Dianthus sylvestris Wulfen (Caryophyllaceae) is frequently found both on serpentine and limestone bedrocks along Apennine chain.
Here we investigated populations of D. sylvestris in North-Center of Italy in order to clarify if phenotypic variation among populations of D. sylvestris, on both serpentine and limestone soils, could be defined as an example of local adaptation or is due to strong phenotypic plasticity. We used a molecular approach based on EST SSR marker to infer on genetic diversity and populations structure. Moreover, to verify if serpentine populations are locally adapteted we use an ecologiac approach based on transplanting field experiment and morphological and physiological measurements.
Population genetic analyses showed a high percentage of polymorphic loci (ranging from 71% to 100%) and the distribution of allele frequencies showed no significant differences among populations from the two soil types. Similarly, allele richness was comparable among populations of serpentine and limestone. Both ANOVA and the low values of differentiation among populations (mean Fst= 0.119, among populations) confirmed the low overall genetic differentiation. Bayesian (STRUCTURE) and multivariate approach (PCoA) ruled out that populations from limestone and serpentine soils cluster in two genetically differentiated groups, even if according to Mantel test, subdivision was on geographic distribution more than on edaphic base. Thus, no evident genetic differentiation among D. sylvestris populations from serpentine and limestone was found with neutral markers.
To determine the contribution of selective factors and/or phenotypic plasticity to local adaptation of D. sylvestris to serpentine, from populations already examined in the genetic analysis, we estimated the metal content in plant aerial parts, collected data on morphological traits, and performed field reciprocal transplantations. High metal content (Ni, Cr) in plants aerial part confirmed, as in previous studies, the bioaccumulation of heavy metals in D. sylvestris plants from serpentine soils. In these plants, several morphological traits were found statistically decreased when compared to plants from limestone so highlighting that serpentine is a less permissive habitat than limestone. However, most of the morphological differences disappeared in transplanted individuals suggesting a large contribution of phenotypic plasticity in determining the observed morphological divergences. Nevertheless, in transplanted plants from serpentine soil to limestone, a two-way ANOVA resulted in a significant difference in biomass with an effect of the original soil on the transplanting soil. Significant differences were also found in flowering time, as plants from serpentine, when transplanted on limestone, flowered before than resident limestone plants. These differences, persisting independently from the original soil type, should have genetic bases. Thus genetic differentiation of populations of D. sylvestris is occurred at least in a few selected loci determining different affinity for the two habitats. This divergence is maintained among populations from different soil types even in the face of extensive gene flow as observed at neutral loci
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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