Age-specific variation of resistance to oxidative stress in the greater flamingo (Phoenicopterus ruber roseus)

Birds exhibit exceptional longevity and are thus regarded as a convenient model to study the intrinsic mechanisms of aging. The oxidative stress theory of aging suggests that individuals age because molecules, cells, tissues, organs, and, ultimately, animals accumulate oxidative damage over time. Accumulation of damage progressively reduces the level of antioxidant defences that are expected to decline with age. To test this theory, we measured the resistance of red blood cells to free radical attack in a captive population of greater flamingo (Phoenicopterus ruber roseus) of known age ranging from 0.3 to 45 years. We observed a convex relationship with young adults (12-20 years old) having greater resistance to oxidative stress than immature flamingos (5 months old) and old flamingos (30-45 years old). Our results suggest that the antioxidant detoxifying system must go through a maturation process before being completely functional. It then declines in older adults, supporting the oxidative theory of aging. Oxidative stress could hence play a significant role in shaping the pattern of senescence in a very long-lived bird species.

Plant functional and phylogenetic turnover correlate with climate and land use in the Western Swiss Alps

Understanding the relative importance of historical and environmental processes in the structure and composition of communities is one of the longest quests in ecological research. Increasingly, researchers are relying on the functional and phylogenetic β-diversity of natural communities to provide concise explanations on the mechanistic basis of community assembly and the drivers of trait variation among species. The present study investigated how plant functional and phylogenetic β-diversity change along key environmental and spatial gradients in the Western Swiss Alps. Methods Using the quadratic diversity measure based on six functional traits: specific leaf area (SLA), leaf dry matter content (LDMC), plant height (H), leaf carbon content (C), leaf nitrogen content (N), and leaf carbon to nitrogen content (C/N) alongside a species-resolved phylogenetic tree, we relate variations in climate, spatial geographic, land use and soil gradients to plant functional and phylogenetic turnover in mountain communities of the Western Swiss Alps. Important findings Our study highlights two main points. First, climate and land use factors play an important role in mountain plant community turnover. Second, the overlap between plant functional and phylogenetic turnover along these gradients correlates with the low phylogenetic signal in traits, suggesting that in mountain landscapes, trait lability is likely an important factor in driving plant community assembly. Overall, we demonstrate the importance of climate and land use factors in plant functional and phylogenetic community turnover, and provide valuable complementary insights into understanding patterns of β-diversity along several ecological gradients.

Geographical and altitudinal population genetic structure of two dung fly species with contrasting mobility and temperature preference.

Local adaptation of populations requires some degree of spatio-temporal isolation. Previous studies of the two dung fly species Scathophaga stercoraria and Sepsis cynipsea have revealed low levels of geographic and altitudinal genetic differentiation in quantitative life history and morphological traits, but instead high degrees of phenotypic plasticity. These patterns suggest that gene flow is extensive despite considerable geographic barriers and large spatio-temporal variation in selection on body size and related traits. In this study we addressed this hypothesis by investigating genetic differentiation of dung fly populations throughout Switzerland based on the same 10 electrophoretic loci in each species. Overall, we found no significant geographic differentiation of populations for either species. This is inconsistent with the higher rates of gene flow expected due to better flying capacity of the larger S. stercoraria. However, heterozygote deficiencies within populations indicated structuring on a finer scale, seen for several loci in S. cynipsea, and for the locus PGM (Phosphoglucomutase) in S. stercoraria. Additionally, S. cynipsea showed a tendency towards a greater gene diversity at higher altitudes, mediated primarily by the locus MDH (malate dehydrogenase), at which a second allele was only present in populations above 1000 m. This may be caused by increased environmental stress at higher altitudes in this warm-adapted species. MDH might thus be a candidate locus subject to thermal selection in this species, but this remains to be corroborated by direct evidence. In S. stercoraria, no altitudinal variation was found.

Bioinformatics-driven identification and examination of candidate genes for non-alcoholic fatty liver disease.

ObjectiveCandidate genes for non-alcoholic fatty liver disease (NAFLD) identified by a bioinformatics approach were examined for variant associations to quantitative traits of NAFLD-related phenotypes.Research Design and MethodsBy integrating public database text mining, trans-organism protein-protein interaction transferal, and information on liver protein expression a protein-protein interaction network was constructed and from this a smaller isolated interactome was identified. Five genes from this interactome were selected for genetic analysis. Twenty-one tag single-nucleotide polymorphisms (SNPs) which captured all common variation in these genes were genotyped in 10,196 Danes, and analyzed for association with NAFLD-related quantitative traits, type 2 diabetes (T2D), central obesity, and WHO-defined metabolic syndrome (MetS).Results273 genes were included in the protein-protein interaction analysis and EHHADH, ECHS1, HADHA, HADHB, and ACADL were selected for further examination. A total of 10 nominal statistical significant associations (P<0.05) to quantitative metabolic traits were identified. Also, the case-control study showed associations between variation in the five genes and T2D, central obesity, and MetS, respectively. Bonferroni adjustments for multiple testing negated all associations.ConclusionsUsing a bioinformatics approach we identified five candidate genes for NAFLD. However, we failed to provide evidence of associations with major effects between SNPs in these five genes and NAFLD-related quantitative traits, T2D, central obesity, and MetS.

Karyotypic variation between wood mouse species: banded chromosomes of Apodemus alpicola and A-microps

The banding pattern (G-, C-, AgNOR-staining) was described in karyotypes of Apodemus alpicola Heinrich, 1952 and A. microps Kratochvil et Rosicky, 1952 collected from the Alps and central Europe, Distinct differences between the two species were revealed in the distribution of C-heterochromatic regions in autosomes and the sex chromosomes, and the distribution of nucleolar organizer regions (NORs). Extensive variation in the distribution pattern of C-heterochromatin and NORs obviously exists among the wood mice of the subgenus Sylvaemus, and individual species can be distinguished according to a specific variation pattern. However, it seems premature to designate individual karyotypic forms as separate species, because the extent of overall geographical interpopulation variation is still not sufficiently known.

Pulse pressure variation-guided fluid therapy after cardiac surgery: A pilot before-and-after trial.

PURPOSE: The aim of this study is to study the feasibility, safety, and physiological effects of pulse pressure variation (PPV)-guided fluid therapy in patients after cardiac surgery. MATERIALS AND METHODS: We conducted a pilot prospective before-and-after study during mandatory ventilation after cardiac surgery in a tertiary intensive care unit. We introduced a protocol to deliver a fluid bolus for a PPV ≥13% for at least >10 minutes during the intervention period. RESULTS: We studied 45 control patients and 53 intervention patients. During the intervention period, clinicians administered a fluid bolus on 79% of the defined PPV trigger episodes. Median total fluid intake was similar between 2 groups during mandatory ventilation (1297 mL [interquartile range 549-1968] vs 1481 mL [807-2563]; P = .17) and the first 24 hours (3046 mL [interquartile range 2317-3982] vs 3017 mL [2192-4028]; P = .73). After adjusting for several baseline factors, PPV-guided fluid management significantly increased fluid intake during mandatory ventilation (P = .004) but not during the first 24 hours (P = .47). Pulse pressure variation-guided fluid therapy, however, did not significantly affect hemodynamic, renal, and metabolic variables. No serious adverse events were noted. CONCLUSIONS: Pulse pressure variation-guided fluid management was feasible and safe during mandatory ventilation after cardiac surgery. However, its advantages may be clinically small.

Potential hosts number in cuckoo bees (Psithyrus subgen.) increases toward higher elevations

In severe and variable conditions, specialized resource selection strategies should be less fre‐ quent because extinction risks increase for species that depend on a single and unstable resource. Psithyrus (Bombus subgenus Psithyrus) are bumblebee parasites that usurp Bombus nests and display inter‐specific variation in the number of hosts they parasitize. Using a phylogenetic comparative frame‐ work, we show that Psithyrus species at higher elevations display a higher number of hosts species com‐ pared with species restricted to lower elevations. Species inhabiting high elevations also cover a larger temperature range, suggesting that species able to occur in colder conditions may benefit from recruit‐ ment from populations occurring in warmer conditions. Our results provide evidence for an 'altitudinal niche breadth hypothesis' in parasitic species, showing a decrease in the parasites' specialization along the elevational gradient, and also suggesting that Rapoport's rule might apply to Psithyrus.

A genome-to-genome analysis of associations between human genetic variation, HIV-1 sequence diversity, and viral control.

HIV-1 sequence diversity is affected by selection pressures arising from host genomic factors. Using paired human and viral data from 1071 individuals, we ran >3000 genome-wide scans, testing for associations between host DNA polymorphisms, HIV-1 sequence variation and plasma viral load (VL), while considering human and viral population structure. We observed significant human SNP associations to a total of 48 HIV-1 amino acid variants (p<2.4 × 10(-12)). All associated SNPs mapped to the HLA class I region. Clinical relevance of host and pathogen variation was assessed using VL results. We identified two critical advantages to the use of viral variation for identifying host factors: (1) association signals are much stronger for HIV-1 sequence variants than VL, reflecting the 'intermediate phenotype' nature of viral variation; (2) association testing can be run without any clinical data. The proposed genome-to-genome approach highlights sites of genomic conflict and is a strategy generally applicable to studies of host-pathogen interaction. DOI:http://dx.doi.org/10.7554/eLife.01123.001.

Association of genetic variation with systolic and diastolic blood pressure among African Americans: the Candidate Gene Association Resource study.

The prevalence of hypertension in African Americans (AAs) is higher than in other US groups; yet, few have performed genome-wide association studies (GWASs) in AA. Among people of European descent, GWASs have identified genetic variants at 13 loci that are associated with blood pressure. It is unknown if these variants confer susceptibility in people of African ancestry. Here, we examined genome-wide and candidate gene associations with systolic blood pressure (SBP) and diastolic blood pressure (DBP) using the Candidate Gene Association Resource (CARe) consortium consisting of 8591 AAs. Genotypes included genome-wide single-nucleotide polymorphism (SNP) data utilizing the Affymetrix 6.0 array with imputation to 2.5 million HapMap SNPs and candidate gene SNP data utilizing a 50K cardiovascular gene-centric array (ITMAT-Broad-CARe [IBC] array). For Affymetrix data, the strongest signal for DBP was rs10474346 (P= 3.6 × 10(-8)) located near GPR98 and ARRDC3. For SBP, the strongest signal was rs2258119 in C21orf91 (P= 4.7 × 10(-8)). The top IBC association for SBP was rs2012318 (P= 6.4 × 10(-6)) near SLC25A42 and for DBP was rs2523586 (P= 1.3 × 10(-6)) near HLA-B. None of the top variants replicated in additional AA (n = 11 882) or European-American (n = 69 899) cohorts. We replicated previously reported European-American blood pressure SNPs in our AA samples (SH2B3, P= 0.009; TBX3-TBX5, P= 0.03; and CSK-ULK3, P= 0.0004). These genetic loci represent the best evidence of genetic influences on SBP and DBP in AAs to date. More broadly, this work supports that notion that blood pressure among AAs is a trait with genetic underpinnings but also with significant complexity.

Lack of seasonal variation in cardiovascular mortality in a country near the equator

Introduction: Mortality from cardiovascular disease (CVD) varies according to seasons in countries that are located far away from the equator, likely linked to concomitant seasonal variation in underlying CVD risk factors. We assessed temporal variation in CVD mortality in the Seychelles, a small island state situated near the equator and where the climate is virtually constant throughout the year. Seychelles is one of the few countries located near the equator where all deaths are registered. Methods: We recoded all deaths along broad causes, including CVD (n=5643), stroke (2112) and myocardial infarction (MI, 804). Stroke and MI were considered as the cause of death if the diagnosis appeared in any of the four fields for underlying causes of death in the death certificates. In view of the small size of the population, we pooled all deaths (n=13'163) between 1989 and 2010. Results: Mortality for all CVD, stroke and MI did not systematically vary according to month or season (chi square >0.05). A lack of variation was also observed within sex and age categories. Conclusion: The lack of seasonal variation in CVD mortality in a country located near the equator is consistent with the hypothesis that seasonal variation in CVD decreases along decreasing a country's latitude.

Population demography of an endangered lizard, the Blue Mountains Water Skink.

BACKGROUND: Information on the age structure within populations of an endangered species can facilitate effective management. The Blue Mountains Water Skink (Eulamprus leuraensis) is a viviparous scincid lizard that is restricted to < 40 isolated montane swamps in south-eastern Australia. We used skeletochronology of phalanges (corroborated by mark-recapture data) to estimate ages of 222 individuals from 13 populations. RESULTS: These lizards grow rapidly, from neonatal size (30 mm snout-vent length) to adult size (about 70 mm SVL) within two to three years. Fecundity is low (mean 2.9 offspring per litter) and is affected by maternal body length and age. Offspring quality may decline with maternal age, based upon captive-born neonates (older females gave birth to slower offspring). In contrast to its broadly sympatric (and abundant) congener E. tympanum, E. leuraensis is short-lived (maximum 6 years, vs 15 years for E. tympanum). Litter size and offspring size are similar in the two species, but female E. leuraensis reproduce annually whereas many E. tympanum produce litters biennially. Thus, a low survival rate (rather than delayed maturation or low annual fecundity) is the key reason why E. leuraensis is endangered. Our 13 populations exhibited similar growth rates and population age structures despite substantial variation in elevation, geographic location and swamp size. However, larger populations (based on a genetic estimate of effective population size) contained older lizards, and thus a wider variance in ages. CONCLUSION: Our study suggests that low adult survival rates, as well as specialisation on a rare and fragmented habitat type (montane swamps) contribute to the endangered status of the Blue Mountains Water Skink.

Going the distance: human population genetics in a clinal world.

Global human genetic variation is greatly influenced by geography, with genetic differentiation between populations increasing with geographic distance and within-population diversity decreasing with distance from Africa. In fact, these 'clines' can explain most of the variation in human populations. Despite this, population genetics inferences often rely on models that do not take geography into account, which could result in misleading conclusions when working at global geographic scales. Geographically explicit approaches have great potential for the study of human population genetics. Here, we discuss the most promising avenues of research in the context of human settlement history and the detection of genomic elements under natural selection. We also review recent technical advances and address the challenges of integrating geography and genetics.

Ontogeny of Sleeping in Color - Linking melanism to sleep architecture and rhythmicity variation in wild barn owl nestlings

The function of sleep remains unknown. To gain insight into the function of sleep in natural conditions, I assessed variation in sleep architecture and its link with fitness-related phenotypic traits. I considered melanin-based coloration because its underlying genetic basis is very well known giving an opportunity to examine whether some genes pleiotropically regulate both coloration and sleep. The melanocortin system is known to generate covariation between melanin-based coloration and other phenotypes like behaviour, physiology and life history traits. I investigated whether this system of genes could participate in the co-expression of coloration and sleep. I carried out a study with nestling barn owls (Tyto alba) in order to tackle the potential link between variation in color traits and the ontogeny of sleep under natural conditions. For this I established a suitable method for recording the brain activity (electroencephalogram) of owls in nature. Birds are especially interesting, because they convergently evolved sleep states similar to those exhibited by mammals. As in mammals, I found that in owlets time spent in rapid eye movement (REM) sleep declines with age, a relationship thought to eflect developmental changes in the brain. Thus this developmental trajectory appears to reflect a fundamental feature of sleep. Additionally, I discovered an association between a gene involved in melanism expressed in the feather follicles (proprotein convertase subtilisin/kexin type 2, PCSK2) and the age-related changes in sleep in the brain. Nestlings with higher expression levels of PCSK2 showed a more precocial pattern of sleep development and a higher degree of melanin-based coloration compared to nestlings with lower PCSK2 expression. Also sleep architecture and the development of rhythmicity in brain and physical activity was related to plumage traits of the nestlings and their biological parents. This pattern during ontogeny might reflect differences in life l history strategies, antipredator behaviour and developmental pace. Therefore, differently colored individuals may differentially deal with trade-offs between the costs and benefits of sleep which in turn lead to differences in brain organization and ultimately fitness. These results should stimulate evolutionary biologists to consider sleep as a major life history trait. Résumé La fonction du sommeil reste inconnue. Afin d'acquérir une meilleur compréhension de la fonction du sommeil dans les conditions naturelles, j'ai analysé la variation dans l'architecture du sommeil et son lien avec d'autres traits phénotypiques liés au succès reproducteur (fitness). J'ai choisi et examiné la coloration mélanique, car ses bases génétiques sont bien connues et il est ainsi possible d'étudier si certains gènes, de façon pléiotropique régulent à la fois la coloration et le sommeil. J'ai exploré si ce système génétique était impliqué dans la co-expression de la coloration et du sommeil. J'ai effectué mon étude sur des poussins de chouette effraie (Tyto alba) en condition naturelle, pour rechercher ce lien potentiel entre la variation de la coloration et l'ontogenèse du sommeil. Dans ce but, j'ai établi une méthodologie permettant d'enregistrer l'activité cérébrale (électroencéphalogramme) des chouettes dans la nature. Les oiseaux sont particulièrement intéressants car ils ont développé, par évolution convergente, des phases de sommeil similaires à celles des mammifères. De manière semblable à ce qui a été montré chez les mammifères, j'ai découvert que le temps passé dans le sommeil paradoxal diminue avec l'âge des poussins. On pense que ceci est dû aux changements développementaux au niveau du cerveau. Cette trajectoire développementale semble refléter une caractéristique fondamentale du sommeil. J'ai également découvert une association entre l'un des gènes impliqué dans le mélanisme, exprimé dans les follicules plumeux (proprotein convertase subtilisin/kexin type 2, PCSK2), et les changements dans la structure du sommeil avec l'âge. Les poussins ayant un niveau d'expression génétique élevé de la PCSK2 présentent une structure du sommeil plus précoce et un taux de coloration dû à la mélanine plus élevé que des poussins avec un niveau d'expression moindre de la PCSK2. L'architecture du sommeil et le développement de la rythmicité dans le cerveau ainsi que l'activité physique sont également liés à la coloration des plumes des poussins et pourraient ainsi refléter des différences de stratégies d'histoire de vie, de comportements anti-prédateur et de vitesses développementales. Ainsi, des individus de coloration différente sembleraient traiter différemment les coûts et les bénéfices du sommeil, ce qui aurait des conséquences sur l'organisation cérébrale et pour finir, sur le succès reproducteur. Ces résultats devraient encourager les biologistes évolutionnistes à considérer le sommeil comme un important trait d'histoire de vie. Zusammenfassung Die Funktion von Schlaf ist noch unbekannt. Um mehr Einsicht in diese unter natürlichen Bedingungen zu bekommen, habe ich die Variation in der Schlafarchitektur und die Verknüpfung mit phänotypischen Merkmalen, die mit der Fitness zusammenhängen, studiert. Ich habe mir melanin-basierte Färbung angesehen, da die zugrunde liegende genetische Basis bekannt ist und somit die Möglichkeit gegeben ist, zu untersuchen, ob einige Gene beides regulieren, Färbung und Schlaf. Das melanocortin System generiert eine Kovariation zwischen melanin-basierter Färbung und anderen phänotypischer Merkmale wie Verhalten, Physiologie und Überlebensstrategien. Ich habe untersucht, ob dieses Gensystem an einer gleichzeitigen Steuerung von Färbung und Schlaf beteiligt ist. Dazu habe ich Schleiereulen (Tyto alba) studiert um einen möglichen Zusammenhang zwischen der Variation in der Pigmentierung und der Entwicklung des Schlafs unter natürlichen Bedingungen zu entdecken. Für diese Studie entwickelte ich eine Methode um die Gehirnaktivität (Elektroenzephalogramm) bei Eulen in der Natur aufzunehmen. Vögel sind besonders interessant, da sie die gleichen Schlafstadien aufweisen wie Säugetiere und diese unabhängig konvergent entwickelt haben. Genauso wie bei Säugetieren nahm die Dauer des sogenannten ,,rapid eye movement" (REM) - Schlafes mit zunehmendem Alter ab. Es wird angenommen, dass dieser Zusammenhang die Entwicklung des Gehirns widerspiegelt. Daher scheint dieses Entwicklungsmuster ein fundamentaler Aspekt von Schlaf zu sein. Zusätzlich entdeckte ich einen Zusammenhang zwischen der Aktivität eines Gens in den Federfollikeln (proprotein convertase subtilisin/kexin type 2, PCSK2), das für die Ausprägung schwarzer Punkte auf den Federn der Eulen verantwortlich ist, und den altersabhängigen Änderungen im Schlafmuster im Gehirn. Küken mit höherer Aktivität von PCSK2 zeigten eine frühreifere Schlafentwicklung und eine dunklere Färbung als Küken mit niedriger PCSK2 Aktivität. Die Architekture des Schlafes und die Entwicklung der Rhythmik im Gehirn und die der physischen Aktivität ist mit der Färbung des Gefieders von den Küken und ihren Eltern verknüpft. Dieses Muster während der Entwicklung kann Unterschiede in Überlebensstrategien, Feindabwehrverhalten und in der Entwicklungsgeschwindigkeit reflektieren. Unterschiedlich gefärbte Individuen könnten unterschiedliche Strategien haben um zwischen den Kosten und Nutzen von Schlaf zu entscheiden, was zu Unterschieden in der Gehirnstruktur führen kann und letztendlich zur Fitness. Diese Ergebnisse sollten Evolutionsbiologen stimulieren Schlaf als einen wichtigen Bestandteil des Lebens zu behandeln.