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Understanding global biodiversity patterns is one of the main objectives of ecology. Spatial variation in species richness can be explained by several environmental factors. The relationships between species richness and environmental factors have been associated with latitudinal, longitudinal and elevational gradients. The number of species is determined by birth, death and migration rates of species in a given area. These rates are affected by abiotic and biotic factors acting at local and regional scales. Climatic seasonal variation may also influence biodiversity, directly through physiological limitations and indirectly through biotic interactions, vegetation structure and food availability. Climate and land use change are the main factors for landscape simplification and biotic homogenization. Thus, the study of community patterns across environmental gradients may help to predict the effect of projected environmental change.
I investigated how abiotic and biotic factors influence different facets of bird diversity across an elevational gradient. My study was conducted along an elevational gradient spanning 2000 m within and around Podocarpus National Park and San Francisco reserve on the southeastern slope of the Andes in Ecuador. The climate is humid tropical montane with a bimodal rain regime. The region is characterized by evergreen premontane forest at low elevations, evergreen lower montane forest at mid elevations and upper montane forest at high elevations. The elevational gradient has natural continuous forests within the protected reserves and fragmented forests surrounding the reserves in a matrix of cattle pastures. To monitor bird diversity, I placed nine 20-m radius point counts within 18 one-hectare plots, in continuous and fragmented forest at 1000, 2000 and 3000 m a.s.l. I recorded and identified all birds for 10 minutes within each point count. Bird communities were sampled eight times per plot, in the most humid season and in the least humid season of 2014 and 2015. To estimate flower and fruit availability, I recorded all plants with open flowers and ripe fruits within each point count. To obtain the relative invertebrate availability, I assessed understory invertebrate fresh biomass using a standardized sweep-netting design along 100-metre borders of each plot. Vertical vegetation heterogeneity was estimated at eight layers above the ground within each point count. Temperature for each plot was obtained using an air temperature regionalization tool and precipitation through remote sensing techniques and meteorological data.
In the first chapter of this thesis, I explored the effects of elevation, climate and vegetation structure on overall bird communities as well as on frugivorous and insectivorous birds. I found that elevation was mostly indirectly associated with bird diversity, jointly mediated via temperature, precipitation and vegetation structure. Additionally, elevation was directly and positively associated with both the overall bird community and with insectivores, but not with frugivores. My findings indicate a reduction of bird diversity due to climatic factors and vegetation structure with increasing elevation. However, the direct, positive effect of elevation suggests that bird diversity was higher than expected towards high elevations, probably due to spatial, biotic and evolutionary settings.
In the second chapter, I analysed the influence of climate and resource availability on temporal variation of bird communities. I found a higher bird diversity in the least humid season than in the most humid season. The seasonality of the bird communities was mainly driven by temperature and precipitation. While temperature had a significant positive effect at high elevations, precipitation had a significant negative effect at low elevations. Resource availability had no significant effect. My findings suggest that the temporal fluctuations in bird communities likely occur due to climate
constraints rather than due to resource limitations.
In the third chapter, I studied the effect of forest fragmentation on taxonomic and functional bird diversity. I found that taxonomic diversity was higher in fragmented compared to continuous forests, while functional diversity was negatively affected by fragmentation, but only at low elevations. The increase of taxonomic diversity in disturbed habitats suggests an increase of habitat generalists, which may compensate the loss of forest specialists. My findings suggest that taxonomic diversity can be uncoupled from functional diversity in diverse communities at low elevations.
My results show the effects of environmental factors on the spatio-temporal patterns of bird communities and the potentially uncoupled responses of taxonomic and functional diversity to forest fragmentation. My findings highlight that bird communities respond differently to abiotic and biotic factors across elevational gradients. Overall, my study helps to better understand the mechanisms that drive species communities in response to complex environmental conditions, which could be an essential contribution for the conservation of bird communities in the tropical Andes.
Background: Definitive chemoradiotherapy (CRT) is the primary treatment for non-metastatic anal squamous cell carcinoma (ASCC). Despite favorable treatment outcomes in general, failure rates up to 40% occur in locally advanced disease. For treatment escalation or de-escalation strategies easily assessable and valid biomarkers are needed.
Methods: We identified 125 patients with ASCC treated with standard CRT at our department. C-reactive protein (CRP) to albumin ratio (CAR) was calculated dividing baseline CRP by baseline albumin levels. We used maximally selected rank statistics to dichotomize patients to high and low risk groups. Associations of CAR with clinicopathologic parameters were evaluated and the prognostic impact was tested using univariate and multivariate cox regression analysis. In a subset of 78 patients, pretreatment tumor tissue was available and CD8+ tumor infiltrating lymphocytes (TILs) and p16INK4a status were scored by immunohistochemistry and correlated with CAR.
Results: Advanced T-stage and male gender were significantly associated with higher baseline CAR. Using the calculated cutoff of 0.117, a high baseline CAR was also associated with worse locoregional control (p = 0.002), distant metastasis-free survival (p = 0.01), disease-free survival (DFS, p = 0.002) and overall survival (OS, p < 0.001). A combined risk score incorporating N-stage and CAR, termed N-CAR score, was associated with worse outcome across all endpoints and in multivariate analysis independent of T-stage and Gender (HR 4.27, p = 0.003). In the subset of 78 patients, a strong infiltration with intratumoral CD8+ TIL was associated with a significantly lower CAR (p = 0.007). CAR is an easily accessible biomarker that is associated with DFS. Our study revealed a possible link between chronic systemic inflammation and an impaired intratumoral immune response.
Ataxia telangiectasia (A-T) is a devastating multi-system disorder characterized by progressive cerebellar ataxia, immunodeficiency, genetic instability, premature aging and growth retardation. Due to better care the patients get older than in the past and new disease entities like disturbed glucose tolerance and liver disease emerge. The objective of the present investigation is to determine the evolution of liver disease and its relation to age and neurological deterioration. The study included 67 patients aged 1 to 38 years with classical A-T. At least two measurements of liver enzymes were performed within a minimum interval of 6 months in 56 patients. The median follow-up period was 4 years (1–16 years). A total of 316 liver enzyme measurements were performed. For analysis, patients were divided into two age groups (Group 1: <12 years; group 2: ≥12 years). In addition, ultrasound of the liver and Klockgether Ataxia Score (KAS) were analyzed. We found significantly higher levels of alpha-fetoprotein (AFP) (226,8 ± 20.87 ng/ml vs. 565,1 ± 24.3 ng/ml, p < 0.0001), and liver enzymes like ALT (23.52 ± 0.77 IU/L vs. 87.83 ± 5.31 IU/L, p < 0.0001) in patients in group 2. In addition, we could show a significant correlation between age and AFP, GGT, and KAS. Ultrasound revealed hepatic steatosis in 11/19 (57.9%) patients in group 2. One female patient aged 37 years died due to a hepato-cellular carcinoma (HCC). Liver disease is present in the majority of older A-T patients. Structural changes, non-alcoholic fatty liver disease and fibrosis are frequent findings. Progress of liver disease is concomitant to neurological deterioration.
Stress often has a negative influence on sports performance. Stress-induced decreases in performance can be especially disastrous for risk sports athletes, who often put their life at risk when practicing their sport. Therefore, it is of great importance to identify protective factors in stressful situations in risk sports. On average, risk sports athletes score extremely high on the personality trait sensation seeking. At the same time, theoretical considerations about dispositional mindfulness suggest that mindful athletes can handle stress more effectively. The main goal of this experiment is to examine the influence of sensation seeking and mindfulness on the stress response to a risk sport-specific stressor. To induce stress, 88 male students completed the Heidelberg Risk Sport-Specific Stress Test (HRSST) which utilizes fear of falling as the stressful event during a climbing exercise. Psychological (anxiety) and physiological (cortisol) responses were measured at multiple time points before and after the HRSST to determine the severity of the stress response. In reaction to the stressor, a significant increase in self-reported state anxiety, but no significant increase in cortisol were observed. The mindfulness subscale external observation correlated positively with anxiety in the climbing wall, sensation seeking and the anxiety scales after the jump correlated negatively and sensation seeking predicted anxiety subscales after the jump in hierarchical regression analyses. However, mindfulness did not predict anxiety measures. Neither sensation seeking nor mindfulness correlated significantly with cortisol levels. The results suggest that high sensation seekers perceive a risk sport-specific stressor as less stressful. The missing physiological response might be explained by the Cross-Stressor-Adaptation-Hypothesis and particularities of the sample. Good internal observers might be especially aware of their need of stimulation and new experiences, which in turn might explain the higher experience-seeking scores. Future studies should further examine the role of mindfulness in stressful situations and the interaction of its subscales with sensation seeking. The current experiment offers new possibilities for adjoining research fields at the interface between sports sciences, psychology and medicine: The findings can be transferred to high risk professions such as police officers, firefighters and military forces (e.g., for selection processes or for interventions).