1,720,988 research outputs found
Relationships among parasites, physiological stress and personality in the interactions between invasive alien and native species
Full text linkThe thesis explored the interactions between Invasive Alien Species (IAS) and native species in the light of potential effects of parasitic infections, physiological stress and personality on individual fitness (reproductive success/investment).
In particular, this study investigated the interspecific competition between the North American invasive Eastern grey squirrel (Sciurus carolinensis) and the native Eurasian red squirrel (Sciurus vulgaris), describing techniques and methods that successively have been applied to evaluate the relationships between personality, stress and parasite load.
Chapter 1 reported the validation of a method to measure physiological stress in Eurasian red squirrel; Chapter 2 showed the application of this method to evaluate physiological stress in the native species in co-occurrence with Eastern grey squirrels.
Chapter 3 presented estimates of personality of individual squirrels using indirect indices and their validation through correlation with direct personality measurements from arena tests. Chapter 4 examined the methods previously identified to explore the relationship between personality and parasite infections in Eastern grey squirrels.
Reproductive success/investment could be influenced by the cumulative effect of factors analysed above. Chapter 5 presented the application of a staining technique of uterine scars count to estimate fecundity in invasive squirrel populations. Finally, Chapter 6 examined the relationships between parasite load, physiological stress, reproductive success and/or investment and the potential mediatory role of personality
Measurement of fecal glucocorticoid metabolite levels in Eurasian red squirrels (Sciurus vulgaris): effects of captivity, sex, reproductive condition, and season
No full textThe causes and consequences of physiological stress in wildlife are of great interest in a wide range of biological disciplines including understanding how environmental changes affect species fate and persistence. In some areas, the Eurasian red squirrel (Sciurus vulgaris) faces local extinction because of the invasive Eastern gray squirrel (Sciurus carolinensis). Whether or not physiological stress is induced by the presence of invasive species or contributes to local declines in Eurasian red squirrels is unknown. Here, we develop an assay that can be used to quantify physiological stress in fecal samples from Eurasian red squirrels to eventually address these questions. We captured free-living squirrels (6 females, 11 males) and placed them into captivity for 48h. Fecal glucocorticoid metabolite (FGM) concentrations in female and male squirrels were significantly higher 24 and 32h after initial captivity with a lag time to peak excretion ranging from 24 to 36h. We measured FGM concentrations in free-living squirrels (37 females, 45 males) over a 3-year period. Lactating free-living squirrels had higher FGM concentrations compared to nonbreeding or pregnant squirrels but there were no differences in FGM concentrations in males with scrotal and abdominal testes. Free-living squirrels had the highest FGM concentrations in the winter and lowest in the summer (winter > autumn > summer). Squirrels kept in captivity for 4–48h had significantly higher FGM concentrations than free-living squirrels (111 fecal samples from 82 squirrels). FGM concentrations in captive but not wild squirrels were significantly repeatable. We found no sex differences and no association with body mass in FGM concentrations in captive or free-living squirrels. Our results indicate that this assay can accurately quantify physiological stress in Eurasian red squirrels, which may be useful for future studies to document how the invasive Eastern gray squirrel contributes to local extinction
Personality differences between native and invasive populations of the eastern gray squirrel
No full textInvasive alien species are a major threat to global biodiversity, thus recent work has aimed to identify traits of successful invaders to better inform management efforts and predictions of future invasions. Personality and intraspecific behavioral
variation are important characteristics that may mediate individuals’ and species’ invasion success. However, to the best of our knowledge, no study to date has looked at the personality differences between an invasive species in its native and
invasive ranges. Here, we filled this gap by studying the sociality and self-grooming behavior of eastern gray squirrels
(Sciurus carolinensis) in their native range in Northeastern USA and in their invasive range in Italy. We used the open field and mirror-image stimulation tests to assess the personality of 466 unique gray squirrels, including 271 individuals
from the native population and 195 from the invasive population. We found that both the distribution and the median value of sociality significantly differed between populations, with a higher median value of sociality among invasive squirrels,
while the distribution and median of self-grooming, a proxy for stress-coping ability, did not significantly differ between
populations. Overall, we demonstrate that certain personality traits differ between native and invasive populations, highlighting
the importance of considering intraspecific behavioral diversity for the prediction and management of invasive
alien species. We urge further work to elucidate the mechanisms behind such personality differences
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
Living on the edge : morphological and behavioral adaptations to a marginal high-elevation habitat in an arboreal mammal
Full text linkAbstract: Habitats are characterized by different local environmental conditions that influence both behavior and morphology of species, which can result in habitat-dependent phenotypic differences among animals living in heterogeneous environments. We studied 3 alpine populations of Eurasian red squirrels (Sciurus vulgaris), 1 living in a marginal high-elevation habitat at the edge of the species' altitudinal distribution, and 2 occurring in higher-quality habitats. Here, we investigated whether squirrels living in the marginal area differed in 2 morphological parameters (body size and body mass) and/or in the expression of 4 personality traits estimated with an open field test and a mirror image stimulation test (activity, exploration, activity-exploration, and social tendency). Furthermore, we tested whether within-individual variance of the traits (behavioral plasticity) was higher in the edge habitat. Male squirrels in the edge habitat were smaller and weighed less than in the other study areas, while among females, size-habitat relationships were less marked. These sex-specific patterns were explained by a strong association between body mass and reproductive success in female squirrels. Squirrels in the marginal habitat were more active, explorative, and had a more social personality than in the other habitats. However, in contrast to our predictions, behavioral plasticity was smaller in the marginal habitat, but only for the trait exploration. Our results suggest that animals choose the habitat that best fits their personality, and that habitat-related differences in selective pressures may shape animals' morphology
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
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