1,721,148 research outputs found
Wolves & the MHC: variability, hybridization and mate choice in the Italian wolf population
No full textIsolated small populations may experience low adaptability and increased extinction risks due to reduced genetic variability, especially if at important functional genes such as the Major Histocompatibility Complex (MHC). We investigated the variability of three class-II genes (DRB1, DQA1, DQB1) in the Italian wolf population, which was long isolated and is now expanding after a recent bottleneck. Compared to other populations, we still found a remarkable MHC variability, showing signatures of historical selection (high dN/dS ratio). The Italian wolves are known to hybridize with domestic dogs, and dog-derived MHC alleles were detected in some genetically-admixed individuals. Background microsatellite and MHC loci did not show reduced variability due to the recent bottleneck. Thus, the population recovery seems not to be threatened by reduced MHC variation nor by deep introgression of domestic dog alleles.
The observed variability could be also influenced by reproductive patterns, which can rely upon MHC similarity between mates. Based on pedigree data of wild-living packs, as reconstructed from extensive non-invasive genetic sampling, we tested the hypothesis of non-random mate choice in 26 breeding pairs. Results showed an unexpected prevalence of MHC-based assortative mating, with excess of peptide similarity between breeding pair members as compared to random expectations. Moreover, variation in both relatedness and heterozygosity showed significant positive correlations with fitness traits (total offspring, years as reproducers, mean offspring per year) deduced from pedigrees. These findings suggest possible advantages for breeders that are more related at the MHC, but not at the genetic background. This balance of general inbreeding avoidance, MHC-assortative mating and heterozygote advantage can reflect the social structure of the species, potentially maximizing the adaptation to the environmental pressures
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
Molecular phylogeography of European Sciurus vulgaris: refuge within refugia?
No full textThe red squirrel (Sciurus vulgaris) is a well-known forest animal distributed all over
Europe. Still, we are far from having a firm knowledge of the species’ phylogeography.
This study investigates the genetic differentiation of S. vulgaris across the species’ Eurasian
range, using sequence data from the mitochondrial DNA gene (D-loop, 252 base pairs, cytochrome
b, 359 base pairs), and eight variable autosomal microsatellite loci genotyped for 236
individuals. The results reveal the presence of two main mitochondrial phylogroups. The
first clade comprises the individuals from the region of Calabria in southern Italy, belonging
to the subspecies S. v. meridionalis, while the second clade contains the remainder of the studied
individuals. Bayesian analysis of microsatellite genotypes resulted in three main clusterings
corresponding to the three S. vulgaris subspecies: infuscatus, meridionalis and fuscoater.
Geographical distribution of mtDNA haplotypes and mismatch analysis suggest a common
refugium for the red squirrel across most of its present range from which expansion happened
rather rapidly. The genotype mixing of italicus with northern populations could be a residual
of postglacial expansion. The lack of mixing between the Calabrian lineage and the rest of
European red squirrel haplotypes can be seen as evidence for distinct histories throughout
the Pleistocene. Calabrian mtDNA probably diverged in an ice age contraction and
remained isolated from the neighbouring squirrel populations until very recent times
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
The role of food availability, human conflict and landscape features in wolf occupancy process
No full textDespite the recent positive trend of wolves, their conservation is still one of the most important priority in several European countries. The knowledge of mechanisms regulating population dynamics, territory occupancy, interactions with prey and human conflict is a prerequisite of
a proper wolf management both on regional and national spatial scale. During the last two decades, Apennine wolf population has played an important role in the recolonization process both on national and European scale. Italian wolf population was threatened reaching the lowest historical number in the recent past. One hundred wolves survived in few isolated areas of the South-Central Apennines between 1960’s and 1970’s. Afterwards, this population started to increase and expanded northwards. Wolf occupancy process was not continuous in the same extent in each part of the Italian range; recolonization of Tuscan-Emilia-Romagna Apennine by wolves occurred in less than ten years and since 1990’s this area is widespread inhabited by many wolf packs. The same phenomenon has been observed on Western Alps little time later.
Wolves crossed the Ligurian Apennine and recolonized the South-Western Alps at the beginning of 1990’s. Wolf presence rose quickly and the Western Alps were newly colonized by many wolf packs in few years. On the contrary, wolf occupancy process was slow in Liguria region.
Although, since 1987 the first wolf pack was confirmed in the eastern Ligurian Apennine, no wolf pack has been observed in the remaining regional territory till 1997. Moreover wolf presence in Ligurian Apennine is still extremely low despite the presence of available land, with only 6 packs recorded on the whole region (5343 km2). Thus, Liguria region represents a good opportunity to study wolf occurrence and persistence in relation to human and environmental variables as: landscape features, size and distribution of protected areas, prey availability and interactions
with human activities. This research was carried out from 2007 to 2012. The wolf predictive model, computed with Theoretic Information Approach and model selection, confirmed a high level of habitat suitability of the whole Liguria region (60.4%). Moreover Liguria region has a rich and abundant ungulate community composed by wild boar (annual harvest : n=15275), roe deer (regional population size : n=16116), chamois (regional population size : n=880), fallow
deer (regional population size: n=630) and free-grazing livestock (regional population size: sheep and goats=17301; cattle =1576). These data could produce a positive effect on wolf presence. On the other side, the low percentage of regional surface covered by protected areas
(4.7%) and the high consumption of livestock (44.9%vm) revealed by wolf scats analysis could
negatively influence the wolf presence. The high wolf-livestock conflict was also confirmed by many attacks and losses recorded (n. of attacks=196; n. of losses= 406), and by several wolves found dead during the study period (n = 12). Our results suggest that the distribution and size of protected areas and the high level of wolf-human conflict can play a key role in the occurrence and persistence of this species throughout the Liguria region
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