Independent sources of condition dependency and multiple pathways determine a composite trait: lessons from carotenoid‐based plumage colouration

Many colour ornaments are composite traits consisting of at least four components, which themselves may be more complex, determined by independent evolutionary pathways, and potentially being under different environmental control. To date, little evidence exists that several different components of colour elaboration are condition dependent and no direct evidence exists that different ornamental components are affected by different sources of variation. For example, in carotenoid‐based plumage colouration, one of the best‐known condition‐dependent ornaments, colour elaboration stems from both condition‐dependent pigment concentration and structural components. Some environmental flexibility of these components has been suggested, but specifically which and how they are affected remains unknown. Here, we tested whether multiple colour components may be condition dependent, by using a comprehensive 3 × 2 experimental design, in which we carotenoid supplemented and immune challenged great tit nestlings (Parus major) and quantified effects on different components of colouration. Plumage colouration was affected by an interaction between carotenoid availability and immune challenge. Path analyses showed that carotenoid supplementation increased plumage saturation via feather carotenoid concentration and via mechanisms unrelated to carotenoid deposition, while immune challenge affected feather length, but not carotenoid concentration. Thus, independent condition‐dependent pathways, affected by different sources of variation, determine colour elaboration. This provides opportunities for the evolution of multiple signals within components of ornamental traits. This finding indicates that the selective forces shaping the evolution of different components of a composite trait and the trait's signal content may be more complex than believed so far, and that holistic approaches are required for drawing comprehensive evolutionary conclusions.     

Physiological stress links parasites to carotenoid‐based colour signals

Vertebrates commonly use carotenoid‐based traits as social signals. These can reliably advertise current nutritional status and health because carotenoids must be acquired through the diet and their allocation to ornaments is traded‐off against other self‐maintenance needs. We propose that the coloration more generally reveals an individual’s ability to cope with stressful conditions. We tested this idea by manipulating the nematode parasite infection in free‐living red grouse (Lagopus lagopus scoticus) and examining the effects on body mass, carotenoid‐based coloration of a main social signal and the amount of corticosterone deposited in feathers grown during the experiment. We show that parasites increase stress and reduce carotenoid‐based coloration, and that the impact of parasites on coloration was associated with changes in corticosterone, more than changes in body mass. Carotenoid‐based coloration appears linked to physiological stress and could therefore reveal an individual’s ability to cope with stressors.     

Blood parasite infection differentially relates to carotenoid‐based plumage and bill color in the American goldfinch

Male and female American goldfinches (Spinus tristis) express condition‐dependent carotenoid‐based plumage and bill coloration. Plumage color is relatively static, as pigments incorporated into feathers during the spring molt cannot be mobilized thereafter. In contrast, bill color is dynamic, reflecting changes in condition over short time periods. Previous studies have shown that male and female ornaments, though similar in expression, are differentially related to measures of immunocompetence, suggesting that the relationship between ornamentation and parasite infection may differ between the sexes. In this study, we evaluate the relationship between condition‐dependent ornamentation (plumage and bill color) and blood parasite infection in male and female American goldfinches. We captured goldfinches after completion of the pre‐alternate molt and prior to the onset of nesting and assessed prevalence of Trypanosoma parasites via blood smears. Plumage color strongly predicted trypanosome infection: Birds with more colorful plumage were less likely to present infections. In contrast, we detected no relationship between infection and bill color, which in other studies has been shown to dynamically reflect current condition. Sex did not affect the relationship between infection status and either ornament. Together, these results suggest that physiological pathways linking carotenoid ornamentation and infection may vary even within a single species.     

Ultraviolet and carotenoid‐based coloration in the viviparous lizard Zootoca vivipara (Squamata: Lacertidae) in relation to age,sex, and morphology

Lizards display structural and pigment‐based colorations, and their visual system is sensitive to wavelengths of 300–700 nm. However, few studies in squamate reptiles have quantified interindividual colour variation that includes the structural ultraviolet (UV) component (300–400 nm). In the present study, we investigated variability of a ventral UV/yellow–red ornamentation in the common lizard Zootoca vivipara, including an analysis of spatial distribution, as well as sex and age differences. We also investigated whether the expression of coloration is related to body size and condition. Our analyses revealed two distinct patches: a gular patch with a strong UV reflectance and a belly patch with a dominant yellow–red reflectance. Males displayed a less saturated throat coloration with higher UV chroma and UV hue, and had a redder but duller belly coloration than females. Yearlings had less elaborate ornaments than adults, although they already displayed a yellow–red sexual dichromatism on the belly. UV sexual dichromatism was only apparent in adults as a result of a weaker UV reflectance in females, suggesting potential fitness costs of a bright UV coloration in that sex. Different colour traits were related to body size in both sexes, as well as to body condition in males. We discuss the potential evolutionary scenarios leading to the maintenance of this ornament in common lizards. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 128–141.     

Sex and age differences in reflectance and biochemistry of carotenoid‐based colour variation in the great tit Parus major

The plumage coloration in great tits (Parus major) is the subject of much behavioural and ecophysiological research, yet there is a lack of analyses of the natural colour variation and its mechanisms. We used reflectance spectrometry and high‐performance liquid chromatography to explore individual, sexual and age‐related variation in carotenoid coloration and pigmentation, paramount to the often presumed, but rarely substantiated, costs and ‘honesty’ of carotenoid displays. In adults, we found that sex was the strongest predictor of ‘brightness’ (higher in males) and of ‘hue’ (longer wavelength in females). There was no sex difference in ‘carotenoid chroma’ or carotenoid content of feathers which also was unrelated to adult age (1 or 2+ years) and condition. Similar patterns were revealed for nestlings. Regarding the biochemical ‘signal content’, ‘carotenoid chroma’, but not ‘hue’, was significantly related to the carotenoid content (lutein and zeaxanthin) of feathers. These results refute the previously assumed exaggeration of carotenoid pigmentation in male great tits, and question the condition‐dependence of carotenoid coloration in this species. However, the sexual dimorphism in total reflectance or ‘brightness’, most likely due to melanins rather than carotenoids, may have implications for signalling or other adaptive explanations that need to be explored. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 758–765.     

Effects of age‐based movement on the estimation of growth assuming random‐at‐age or random‐at‐length data

Simulation methods were used to generate paired data from a simulated population that included the age‐based process of movement and the length‐based process of gear selection. The age‐based process caused bias in the estimates of growth parameters assuming random at length, even when relatively few age classes were affected. Methods that assumed random at age were biased by the subsequent inclusion of the length‐based process of gear selection. Additional knowledge of the age structure of the sampled area is needed to ensure an unbiased estimate of the growth parameters when using the length‐conditional approach in the presence of age‐based movement. Estimates of the variability in the length‐at‐age relationship were better estimated with the length‐conditional than the traditional method even when the assumptions of random at length were violated. Inclusion of paired observations of length and associated age inside the population dynamics model may be the most appropriate way of estimating growth.     

Evolution of a conspicuous melanin‐based ornament in gulls Laridae

Melanin‐ and carotenoid‐based ornaments often signal different aspects of individual quality or similar components of quality under different environmental conditions and, thus, they may become evolutionarily integrated into a composite sexual trait. On the other hand, functionally and developmentally different characters (e.g. coloration characters of different developmental origin) are more likely to evolve independently from each other than more similar traits. Here, we examined evolutionary correlations between the occurrence of a conspicuous melanin‐based ornament (hood) and carotenoid‐based bare‐part ornaments within gull family. We also aimed to identify major ecological, life‐history and biogeographical predictors of hood occurrence and reconstruct evolutionary history of this ornament. We found that hood occurrence was associated with red or dark coloration of unfeathered traits (bill and legs), whereas combinations of hood with yellow carotenoid‐based coloration of integument were evolutionarily avoided. Also, hood occurrence correlated negatively with the occurrence of other melanin‐based plumage character (mantle). Breeding latitude and habitat were identified as major predictors of hood occurrence in gulls, as hoods were recorded more frequently in low‐latitude and inland (rather than marine) species. Finally, our analysis provided support for evolutionary lability in hood occurrence, with a dominance of transitions towards hood loss in the evolutionary history of gulls. The results of our study provide one of the first evidence for a correlated evolution of melanin‐ and carotenoid‐based ornaments in an avian lineage, which supports evolutionary modularity of developmentally and functionally different coloration traits.     

Corticosterone regulates multiple colour traits in Lacerta [Zootoca] vivipara males

Ornamental colours usually evolve as honest signals of quality, which is supported by the fact that they frequently depend on individual condition. It has generally been suggested that some, but not all types of ornamental colours are condition dependent, indicating that different evolutionary mechanisms underlie the evolution of multiple types of ornamental colours even when these are exhibited by the same species. Stress hormones, which negatively affect condition, have been shown to affect colour traits based on different pigments and structures, suggesting that they mediate condition dependence of multiple ornament types both among and within individuals. However, studies investigating effects of stress hormones on different ornament types within individuals are lacking, and thus, evidence for this hypothesis is scant. Here, we investigated whether corticosterone mediates condition dependence of multiple ornaments by manipulating corticosterone levels and body condition (via food availability) using a two‐factorial design and by assessing their effect on multiple colour traits in male common lizards. Corticosterone negatively affected ventral melanin‐ and carotenoid‐based coloration, whereas food availability did not affect coloration, despite its significant effect on body condition. The corticosterone effect on melanin‐ and carotenoid‐based coloration demonstrates the condition dependence of both ornaments. Moreover, corticosterone affected ventral coloration and had no effect on the nonsexually selected dorsal coloration, showing specific effects of corticosterone on ornamental ventral colours. This suggests that corticosterone simultaneously mediates condition dependence of multiple colour traits and that it therefore accounts for covariation among them, which may influence their evolution via correlational selection.     

Age Dimorphism in the Association between Growth‐Hormone Status and the Respiratory Quotient

Objective: To investigate the impact of age on the association between the respiratory quotient (RQ) and growth‐hormone (GH) secretion and to investigate the acute lipolytic response to an exogenous GH bolus. Research Methods and Procedures: A cross‐sectional study of 36 non‐obese healthy subjects (18 women and 18 men) from two age groups was used: “younger” (mean age, 29.5 years; range, 27 to 34 years) and “older” (mean age, 50.8 years; range, 47 to 59 years). Endogenous GH secretion by means of deconvolution analysis of 24‐hour serum GH concentrations was measured every 20 minutes. Resting RQ was measured after a 12‐hour overnight fast. The lipolytic response to an intravenous exogenous GH bolus (200 μg) was assessed by measuring serum levels of free fatty acids as well as changes in RQ. Additional measurements included body composition (regional computed tomography scan and DXA) and physical fitness (Vo ₂max). Results: Resting RQ did not differ between the two age groups: 0.81 ± 0.01 (young) vs. 0.82 ± 0.01 (older; not significant). Several estimates of GH release correlated positively with RQ in the younger group, whereas a negative correlation was detected in the older subjects [GH production rate (μg/liter × kg) vs. RQ: r = 0.62, p < 0.01 (younger); r = ?0.53; p = 0.02 (older)]. By regression analysis, 52% to 58% of the variation in RQ could be explained by GH status. After an exogenous GH bolus, the incremental response in nonesterified fatty acid was slightly higher in younger individuals (p = 0.09). Discussion: Resting RQ is significantly correlated with GH status. This association is positive in younger individuals and negative in older individuals. The lipolytic response to exogenous GH is moderately higher in younger compared with older individuals. GH status should be taken into account when investigating the residual variation in RQ.     

Individual quality and carotenoid‐based plumage ornaments in male red bishops (Euplectes orix): plumage is not all that counts

Males in many bird species develop elaborate carotenoid‐based plumage ornaments that play an important role as signals of individual quality in intra‐ or intersexual selection. In the present study, we investigated which of several factors related to male condition and health affect the brightness and coloration of the carotenoid‐based orange–red breeding plumage in males of the red bishop (Euplectes orix), a polygynous and sexually dimorphic weaverbird species. The study revealed a very complex pattern, with the relationships between plumage traits and both heterophil‐to‐lymphocyte ratio and blood parasite load varying considerably among seasons, suggesting a strong influence of environmental conditions. Furthermore, overall condition of males strongly affected the association pattern between plumage traits and other factors, with males in bad condition being forced to allocate resources away from plumage elaboration to body maintenance or the enhancement of immune functions, whereas males in good condition can afford to invest in plumage ornamentation without obvious detrimental effects on health. Thus, females cannot rely on plumage characteristics alone to gather information on male quality, but have to assess additional traits that advertise general male health status. Perhaps surprisingly, testosterone levels were not related to male plumage characteristics. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 384–397.     

Obesity and Overweight Prevalence in Polish 7‐ to 9‐Year‐Old Children

Objective: Secular trend in childhood obesity is a well‐known phenomenon, and it is important to monitor it in cross‐sectional studies. The study aim was to estimate prevalence of obesity and overweight in Polish 7‐ to 9‐year‐old children and to compare the results with a French study based on the same protocol. Research Methods and Procedures: The study was conducted in 2001 according to the protocol of the European Childhood Obesity Group. Height and weight were measured, and BMI was calculated to define nutritional status in a randomly selected group of 2916 (1445 girls and 1471 boys) primary school children. Obesity and overweight were estimated according to International Obesity Task Force references with curve for obesity and overweight passing through 30 and 25 kg/m² at age 18, respectively. Results: Overweight (including obesity) was found in 15.4% of Polish children (in 15.8% of girls and 15.0% of boys) and obesity in 3.6% (3.7% of girls and 3.6% of boys) compared with 18.1% of overweight and 3.8% of obese children in French study. There was no significant difference in nutrition status between Polish and French children except for higher frequency of overweight in French 9‐year‐old boys. The same trend of decreasing overweight through age classes was observed in both populations. Discussion: The prevalence of obesity and overweight (including obesity) in prepubertal children estimated in two European countries according to the same protocol and using the same references showed little differences between the two populations despite higher prevalence of obesity in Polish than French adults.     

Family‐based genome scan for age at onset of late‐onset Alzheimer's disease in whole exome sequencing data

Alzheimer's disease (AD) is a common and complex neurodegenerative disease. Age at onset (AAO) of AD is an important component phenotype with a genetic basis, and identification of genes in which variation affects AAO would contribute to identification of factors that affect timing of onset. Increase in AAO through prevention or therapeutic measures would have enormous benefits by delaying AD and its associated morbidities. In this paper, we performed a family‐based genome‐wide association study for AAO of late‐onset AD in whole exome sequence data generated in multigenerational families with multiple AD cases. We conducted single marker and gene‐based burden tests for common and rare variants, respectively. We combined association analyses with variance component linkage analysis, and with reference to prior studies, in order to enhance evidence of the identified genes. For variants and genes implicated by the association study, we performed a gene‐set enrichment analysis to identify potential novel pathways associated with AAO of AD. We found statistically significant association with AAO for three genes (WRN, NTN4 and LAMC3) with common associated variants, and for four genes (SLC8A3, SLC19A3, MADD and LRRK2) with multiple rare‐associated variants that have a plausible biological function related to AD. The genes we have identified are in pathways that are strong candidates for involvement in the development of AD pathology and may lead to a better understanding of AD pathogenesis.     

Insertion site‐based polymorphism markers open new perspectives for genome saturation and marker‐assisted selection in wheat

In wheat, the deployment of marker‐assisted selection has long been hampered by the lack of markers compatible with high‐throughput cost‐effective genotyping techniques. Recently, insertion site‐based polymorphism (ISBP) markers have appeared as very powerful new tools for genomics and genetic studies in hexaploid wheat. To demonstrate their possible use in wheat breeding programmes, we assessed their potential to meet the five main requirements for utilization in MAS: flexible and high‐throughput detection methods, low quantity and quality of DNA required, low cost per assay, tight link to target loci and high level of polymorphism in breeding material. Toward this aim, we developed a programme, IsbpFinder, for the automated design of ISBP markers and adapted three detection methods (melting curve analysis, SNaPshot^® Multiplex System and Illumina BeadArray technology) for high throughput and flexible detection of ISBP or ISBP‐derived SNP markers. We demonstrate that the high level of polymorphism of the ISBPs combined with cost‐effective genotyping methods can be used to efficiently saturate genetic maps, discriminate between elite cultivars, and design tightly linked diagnostic markers for virtually all target loci in the wheat genome. All together, our results suggest that ISBP markers have the potential to lead to a breakthrough in wheat marker‐assisted selection.     

Cross‐transmission of clinical Enterococcus faecium in relation to esp and antibiotic resistance

Aims: To investigate clonality among clinical Enterococcus faecium isolates and normal intestinal microflora isolates as well as cross‐transmission between patients in relation to the presence of the esp gene and antibiotic resistance. Methods and Results: Blood‐culture isolates (n = 101) deriving from tertiary, secondary and primary hospitals were analysed. Antibiotic susceptibility was investigated. Polymerase chain reaction and pulsed‐field gel electrophoresis were used for detection of esp and genotyping, respectively. Nearly half (43%) of the patients included were involved in a cross‐transmission event with Ent. faecium. These strains disseminated both within and between all hospitals. The antibiotic resistance and presence of esp were highest in isolates from the tertiary hospital. Isolates harbouring esp showed less genetic diversity compared with esp negative ones. Conclusions: Cross‐transmission with Ent. faecium between patients was readily detected, indicating that hospital‐adapted clones circulate within and between hospitals. Acquired characteristics, such as antibiotic resistance and esp, seem to accumulate in the isolates disseminating in the tertiary hospital. Significance and Impact of the Study: It is important to characterize Ent. faecium isolates causing infections and to determine the extent of dissemination in order to prevent further spread of these pathogens.     

Field‐based comparison of ligand and coactivator binding sites of nuclear receptors

A structure‐based comparison of the ligand‐binding domains of 35 nuclear receptors from five different subfamilies is presented. Their ligand and coactivator binding sites are characterized using knowledge‐based contact preference fields for hydrophobic and hydrophilic interactions implemented in the MOE modeling environment. Additionally, for polar knowledge‐based field points the preference for negative or positive electrostatic interactions is estimated using the Poisson‐Boltzmann equation. These molecular‐interaction fields are used to cluster the nuclear receptor family based on similarities of their binding sites. By analyzing the similarities and differences of hydrophobic and polar fields in binding pockets of related receptors it is possible to identify conserved interactions in ligand and coactivator binding pockets, which support e.g. design of specific ligands during lead optimization or virtual screening as docking filter. Examples of remarkable similarities between ligand binding sites of members from phylogenetically different nuclear receptor families (RXR, RAR, HNF4, NR5) and differences between closely related subtypes (LXR, RAR, TR) are discussed in more detail. Significant similarities and differences of coactivator binding sites are shown for NR3Cs, LXRs and PPARs. © 2009 Wiley Periodicals, Inc. Biopolymers 91: 884–894, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com