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No description available.

No description available.

Finding the genes that underlie variation in production and developmental traits has important economic applications. Incubation behaviour represents a loss of production in conventional breeds of chicken adapted to local conditions and was what motivated this thesis. The Mendelian traits of comb type, crest, Silkie and normal feathers, feathered leg, fibromelanosis, comb colour, skin and shank colour, feather colour and patterns are of interest because of the insight they give to genes and development and were also investigated in the thesis. We used White Leghorn and Silkie lines of chicken to detect the genetic loci controlling incubation behaviour and Mendelian traits using linkage based analysis in an F2 cross. The evidence for QTL affecting incubation status over the whole period on chromosome 5 was strong (P<0.05). After the addition of 218 new informative SNP markers across the genome including chromosome 5 the 95% confidence interval spanned a region around 45 cM having previously been 95 cM. Three other suggestive QTL for incubation status were found after the addition of SNP markers on chromosome 1, 18, 19, E22C19W28 at 70, 0, 1 and 13cM respectively. The mode of action of the incubation status QTL indicates that the White Leghorn allele was either promoting incubation behaviour or that heterozygotes have performance that exceeds the homozygotes except the QTL on chromosome 1 where the Silkie allele is promoting incubation behaviour as might be expected. A highly significant QTL (P<0.01) for early incubation behaviour (25-30 weeks) was found on chromosome 8 at 18 cM. This QTL has an additive effect with the possession of a Silkie allele increasing the likelihood of incubation behaviour. Other suggestive QTL for early incubation behaviour were found on chromosome 26 and 1 at 0 and 66cM respectively. For Mendelian traits, genome wide significant (P<0.01) genetic loci for comb type, crest type and feather type was found on chromosome 7 at 77cM, linkage group E22C19W28 at 7cM and on chromosome 3 at 169cM respectively. Significant genetic loci (P<0.01) for leg colour and skin colour were found on chromosome 20 at 56cM and 60cM respectively. In the present study, loci for all feather patterns were found on E22C19W28 even after removing animals carrying the dominant white alleles, suggesting dominant white or another allele at the locus was still influential. Comb type and incubation behaviour were investigated at the gene level. Thyroid stimulating hormone receptor (TSHR) is believed to be involved in the process of domestication and was found at the peak position of the most significant QTL on chromosome 5 for incubation behaviour. Functional exploration of Wnt genes as a candidate gene for comb type was investigated by in-situ hybridization in Silkie and White Leghorn embryos. The Wnt6 gene showed expression in the region of the presumptive comb development of embryos. In conclusion, for the first time genetic loci that explain maternal behaviour have been described. The coincidence of the incubation behaviour locus on chromosome 5 with the site of the strongest selective sweep in poultry, the TSHR, and the coincidence of QTL on chromosome 1 and 8 with thyroid hormone activity it would appear that the thyrotrophic axis may be critical to the loss of incubation behaviour and improved reproductive performance with domestication. Further analysis of these loci should be able to produce markers that can reduce the propensity for birds to incubate. Comb type marker might allow introgression of this trait to prevent comb damage in commercial hens.

The purpose of this study is to investigate the similarity in personality traits among students in the same major field of study and the difference in personality traits between students in different fields of major study. Investigation will also be made of the relationship between vocational interests of the subjects and their major fields of study.

The purpose of the present study is to investigate personality traits or trait clusters that will identify academic high and low achievers and differentiate the two.

La schizotypie est un trait de personnalité caractérisé par un niveau subclinique de symptômes de la schizophrénie, avec des caractéristiques dites positives (croyances et perceptions inhabituelles) ou négatives (retrait et anxiété sociale). Cette thèse a pour but de mieux comprendre comment la schizotypie s'articule avec d'autres dimensions psychopathologiques.Dans une première partie nous avons étudié les liens entre schizotypie et traits autistiques dans 2 populations d'étudiants scientifiques au moyen d'analyses par classification. Une première analyse sur la base des traits schizotypiques et autistiques a identifié 4 groupes avec des profils distincts, dont un cluster à haut niveau de traits. Cette combinaison de traits est associée à des signes de dégradation psychopathologique (symptômes anxieux et dépressifs, attachement insécurisé) et à de moindres performances académiques. Une deuxième étude propose une typologie des étudiants en fonction des traits schizotypique, autistique et cyclothymique. Cette typologie fait apparaître un cluster à hauts traits, avec un niveau élevé de symptômes de dépression et d'idéation suicidaire et de moindres résultats universitaires. Ces 2 études suggèrent donc que la combinaison de traits schizotypes et autistiques a une influence négative sur la réussite dans le domaine scientifique, en lien avec une comorbidité dépressive.La deuxième partie établit une typologie du jeune adulte afin de réexaminer le concept de "schizotypie saine", défini comme trait de schizotypie positive sans autre dimensions de la schizotypie. Nos résultats confirment que la shizotypie positive est associée à des bénéfices (e.g., qualité perçue des relations interpersonnelles) mais aussi à des traits de troubles de la personnalité et à des symptômes psychopathologiques, ce qui interpelle le concept de schizotypie saine. Dans une dernière étude nous avons identifié des biais illustrant l’impression que la schizotypie positive est plus saine qu’en réalité. / Schizotypy is a personality trait characterized by subclinical levels of schizophrenia symptoms, including positive (odd beliefs and unusual perceptions) or negative (withdrawal and social anxiety) features. This thesis aimed at a better understanding of how schizotypy articulates with other psychopathological dimensions.As a first part, we studied the links between schizotypy and autistic traits in 2 samples of scientific college students, using a cluster analysis. A first analysis based on schizotypal and autistic dimensions identified 4 groups with distinct profiles, including a cluster with high levels of traits. This combination of traits was associated with significant psychopathological degradation (anxiety and depressive symptoms, insecure attachment) and with lesser academic performances. A second study identified a typology of students based on schizotypal, autistic and cyclothymic traits. This typology showed a high traits cluster with elevated levels of depressive symptoms and suicidal ideations, and lesser academic results. These 2 studies thus suggest that association of schizotypal and autistic traits could impair success in scientific background, in relationship with a depressive comorbidity.The second part identified a typology of young adults aiming at reassessing the concept of "healthy schizotypy", defined as a trait of positive schizotypy without other schizotypal dimensions. Our results confirm that positive schizotypy is associated with benefits (e.g., perceived quality of interpersonal relations) but also with traits of personality disorders and psychopathological symptoms, which questions the concept of healthy schizotypy. In a last study we identified biases illustrating the impression that positive schizotypy may seem healthier than in reality.

Trait-based approaches are useful in ecological research because of their potential ability to predict species responses from patterns present in the community and to infer mechanisms driving community assembly. Current approaches for fishes are lacking traits across all five fundamental niche dimensions (i.e. habitat, life history, trophic, metabolic and defense). This study quantified a broad range of fish functional traits across all five niche dimensions (commonly used traits and novel traits), quantified intra- and interspecific variation for each trait, tested for relationships among traits within and among niche dimensions, tested for phylogenetic conservatism of traits and assessed trait-environment relationships for a subset of these traits under two different contexts. Approximately one third of the quantified traits exhibited greater intraspecific variation than interspecific variation and were not included in subsequent analyses. There were similarities between phylogeny and trait dendrograms for all traits, and habitat, metabolic and defense traits. The traits identified in chapter 2 were able to explain species responses during different flow periods in two intermittent streams as well as species-specific differences in host microbiome at the onset of drought in one intermittent stream. The novel traits identified in chapter 2 did contribute to our understanding of the community assembly dynamics in chapter 3.

Proefschrift--Letteren--Utrecht, 1976. / Bibliogr. p. 178-194.

Wing shape and echolocation are two novel adaptations in the Chiroptera and are strongly influenced by environmental conditions. Wing shape is influenced by environmental clutter. Shorter, broader wings allow for more maneuverable flight, and are advantageous for bats living in highly cluttered environments. Longer, narrower wings help bats to increase flight speed, and are best suited for bats living in more open environments. It is likely that wing shape is also influenced by temperature, given the potential for wings to act as thermoregulatory appendages. Wings provide a thermal gradient across their surfaces, dissipating excess heat from the body. However, the importance in thermoregulation in determining wing size is unknown. If thermoregulation is a strong selective pressure, bats in hotter, more arid regions should have larger wings. Environmental conditions also influence echolocation pulse design. Echolocation pulses must successfully reach a target and generate an audible echo despite atmospheric attenuation. High-duty cycle (HDC) pulses, calls with longer durations than the interval between them, are particularly useful in environments with high amount of environmental clutter. HDC echolocators use an acoustic fovea and Doppler shift compensation to detect the fluttering wings of insect prey in dense vegetation. However, the flexibility of these pulses is limited by the bat's acoustic fovea. Wing shape and echolocation combined form an adaptive complex, providing bats with a highly specialized system of foraging. Climate change poses an enormous risk to a bat's foraging success, because rising ambient temperatures are likely to change the selective pressures on wing size (due to the potential thermoregulatory benefits) as well as prey detection volumes of the bat's echolocation (because sound propagation is influenced by temperature). As an adaptive complex any selection on either wings or echolocation is likely to influence changes in the other, with consequences for the foraging efficiency of bats. The potential impact of climate change on the foraging efficiency of bats can be gauged by the bats' adaptive responses to different climatic conditions over their geographic range. I examined these two traits in different localities across the geographic range of the Cape horseshoe bat, R. capensis to determine if wing and echolocation parameters are adapted to current climatic conditions. I measured wing area and echolocation parameters at sites within the distribution of R. capensis that were representative of the different climates across its range. I measured wing areas using digital image analysis software, and I measured echolocation parameters using a microphone array system. Temperature was a predictor in the top fitting linear mixed effects models for both wing area and prey detection volume. For differences in wing area, body mass was the only significant explanatory variable. However, body mass may itself be influenced by environmental conditions. NDVI, latitude, and average winter minimum temperature significantly related to differences in prey detection volume. My results indicate geographic variation in both wing area and prey detection volume, an indication that these traits are adapted to local climate conditions. Geographic variation in wing area is a consequence of body mass, which may or may not be a function of climate. However, geographic variation in prey detection volume is directly influenced by the environment. Therefore, increases in ambient temperature due to human-induced climate change are likely to have an effect on the foraging efficiency of R. capensis.