A Cautionary Note on "A Cautionary Note on the Use of Ornstein Uhlenbeck Models in Macroevolutionary Studies".

Models based on the Ornstein-Uhlenbeck process have become standard for the comparative study of adaptation. Cooper et al. (2016) have cast doubt on this practice by claiming statistical problems with fitting Ornstein-Uhlenbeck models to comparative data. Specifically, they claim that statistical tests of Brownian motion may have too high Type I error rates and that such error rates are exacerbated by measurement error. In this note, we argue that these results have little relevance to the estimation of adaptation with Ornstein-Uhlenbeck models for three reasons. First, we point out that Cooper et al. (2016) did not consider the detection of distinct optima (e.g. for different environments), and therefore did not evaluate the standard test for adaptation. Second, we show that consideration of parameter estimates, and not just statistical significance, will usually lead to correct inferences about evolutionary dynamics. Third, we show that bias due to measurement error can be corrected for by standard methods. We conclude that Cooper et al. (2016) have not identified any statistical problems specific to Ornstein-Uhlenbeck models, and that their cautions against their use in comparative analyses are unfounded and misleading. [adaptation, Ornstein-Uhlenbeck model, phylogenetic comparative method.].

Seasonal but not sex-biased gene expression of the carotenoid ketolase, CYP2J19, in the sexually dichromatic southern red bishop (Euplectes orix).

Intense red colours in birds are often owing to ketocarotenoids (KCs). In many land birds, KCs are oxidized from dietary yellow precursors, presumably by the avian carotenoid ketolase CYP2J19, the regulation and constraints of which have important implications for condition-dependence and honest signalling of carotenoid colour displays. We investigated hepatic CYP2J19 gene expression in the seasonally and sexually dichromatic southern red bishop (Euplectes orix) in relation to season, sex, progression of the prenuptial moult, testis size, body condition, redness and circulating sex steroids. A coloration function of CYP2J19 is supported by a seasonal upregulation prior to and during the carotenoid-depositing stage of the male prenuptial moult. However, CYP2J19 expression was similarly high in females (which do not moult prenuptially), and remained high in males after moult, suggesting additional or alternative roles of hepatic CYP2J19 or its products, such as detoxification or antioxidant functions. In males, the CYP2J19 upregulation preceded and was unrelated to the rise in plasma testosterone, but was correlated with androstenedione, probably of adrenal origin and compatible with luteinizing hormone-induced and (in females) oestrogen-suppressed moult. Finally, contrary to ideas that carotenoid ketolation rate mediates honest signalling of male quality, CYP2J19 expression was not related to plumage redness or male body condition.

Diverse Wheat-Alien Introgression Lines as a Basis for Durable Resistance and Quality Characteristics in Bread Wheat.

Wheat productivity has been significantly improved worldwide through the incorporation of novel genes from various gene pools, not least from wild relatives of wheat, into the commonly cultivated bread and durum wheat. Here, we present and summarize results obtained from a diverse set of wheat-alien introgression lines with mainly introgressions of rye, but also of Leymus spp. and Thinopyrum junceiforme into bread-wheat (Triticum aestivum L.). From this material, lines carrying 2RL were found with good agronomic performance and multiple resistance not least towards several races of powdery mildew. A novel resistance gene, one of few showing resistance towards all today identified stem rust races, designated Sr59, was also found originating from 2RL. Lines with multiple introgressions from 4R, 5R, and 6R were found resistant towards the majority of the stripe rust races known today. Due to lack of agricultural adaptation in these lines, transfer of useful genes into more adapted wheat material is a necessity, work which is also in progress through crosses with the CSph1b mutant, to be able to only transfer small chromosome segments that carry the target gene. Furthermore, resistance towards Russian wheat aphid was found in lines having a substitution of 1R (1D) and translocations of 3DL.3RS and 5AL.5RS. The rye chromosomes 1R, 2R, and 6R were found responsible for resistance towards the Syrian Hessian fly. High levels of especially zinc was found in several lines obtained from crosses with Leymus racemosus and Leymus mollis, while also some lines with 1R, 2R, or 5R showed increased levels of minerals and in particular of iron and zinc. Moreover, lines with 1R, 2R, 3R, and Leymus spp. introgressions were also found to have a combination of high iron and zinc and low cadmium concentrations. High variation was found both in grain protein concentration and gluten strength, measured as %UPP, within the lines, indicating large variation in bread-making quality. Thus, our study emphasizes the impact that wheat-alien introgression lines can contribute to current wheat lines and shows large opportunities both to improve production, resistance, and quality. To obtain such improvements, novel plant breeding tools, as discussed in this paper, opens unique opportunities, to transfer suitable genes into the modern and adapted wheat cultivars.

Endless forms of sexual selection.

In recent years, the field of sexual selection has exploded, with advances in theoretical and empirical research complementing each other in exciting ways. This perspective piece is the product of a "stock-taking" workshop on sexual selection and sexual conflict. Our aim is to identify and deliberate on outstanding questions and to stimulate discussion rather than provide a comprehensive overview of the entire field. These questions are organized into four thematic sections we deem essential to the field. First we focus on the evolution of mate choice and mating systems. Variation in mate quality can generate both competition and choice in the opposite sex, with implications for the evolution of mating systems. Limitations on mate choice may dictate the importance of direct vs. indirect benefits in mating decisions and consequently, mating systems, especially with regard to polyandry. Second, we focus on how sender and receiver mechanisms shape signal design. Mediation of honest signal content likely depends on integration of temporally variable social and physiological costs that are challenging to measure. We view the neuroethology of sensory and cognitive receiver biases as the main key to signal form and the 'aesthetic sense' proposed by Darwin. Since a receiver bias is sufficient to both initiate and drive ornament or armament exaggeration, without a genetically correlated or even coevolving receiver, this may be the appropriate 'null model' of sexual selection. Thirdly, we focus on the genetic architecture of sexually selected traits. Despite advances in modern molecular techniques, the number and identity of genes underlying performance, display and secondary sexual traits remains largely unknown. In-depth investigations into the genetic basis of sexual dimorphism in the context of long-term field studies will reveal constraints and trajectories of sexually selected trait evolution. Finally, we focus on sexual selection and conflict as drivers of speciation. Population divergence and speciation are often influenced by an interplay between sexual and natural selection. The extent to which sexual selection promotes or counteracts population divergence may vary depending on the genetic architecture of traits as well as the covariance between mating competition and local adaptation. Additionally, post-copulatory processes, such as selection against heterospecific sperm, may influence the importance of sexual selection in speciation. We propose that efforts to resolve these four themes can catalyze conceptual progress in the field of sexual selection, and we offer potential avenues of research to advance this progress.

Evolution of CYP2J19, a gene involved in colour vision and red coloration in birds: positive selection in the face of conservation and pleiotropy.

BACKGROUND: Exaggerated signals, such as brilliant colours, are usually assumed to evolve through antagonistic coevolution between senders and receivers, but the underlying genetic mechanisms are rarely known. Here we explore a recently identified "redness gene", CYP2J19, that is highly interesting in this context since it encodes a carotenoid-modifying enzyme (a C4 ketolase involved in both colour signalling and colour discrimination in the red (long wavelength) spectral region.) RESULTS: A single full-length CYP2J19 was retrieved from 43 species out of 70 avian genomes examined, representing all major avian clades. In addition, CYP2J19 sequences from 13 species of weaverbirds (Ploceidae), seven of which have red C4-ketocarotenoid coloration were analysed. Despite the conserved retinal function and pleiotropy of CYP2J19, analyses indicate that the gene has been positively selected throughout the radiation of birds, including sites within functional domains described in related CYP (cytochrome P450) loci. Analyses of eight further CYP loci across 25 species show that positive selection is common in this gene family in birds. There was no evidence for a change in selection pressure on CYP2J19 following co-option for red coloration in the weaverbirds. CONCLUSIONS: The results presented here are consistent with an ancestral conserved function of CYP2J19 in the pigmentation of red retinal oil droplets used for colour vision, and its subsequent co-option for red integumentary coloration. The cause of positive selection on CYP2J19 is unclear, but may be partly related to compensatory mutations related to selection at the adjacent gene CYP2J40.

Expression of a carotenoid-modifying gene and evolution of red coloration in weaverbirds (Ploceidae).

Red carotenoid colours in birds are widely assumed to be sexually selected quality indicators, but this rests on a very incomplete understanding of genetic mechanisms and honesty-mediating costs. Recent progress was made by the implication of the gene CYP2J19 as an avian carotenoid ketolase, catalysing the synthesis of red C4-ketocarotenoids from yellow dietary precursors, and potentially a major mechanism behind red coloration in birds. Here, we investigate the role of CYP2J19 in the spectacular colour diversification of African weaverbirds (Ploceidae), represented by five genera and 16 species: eight red, seven yellow and one without carotenoid coloration. All species had a single copy of CYP2J19, unlike the duplication found in the zebra finch, with high expression in the retina, confirming its function in colouring red oil droplets. Expression was weak or undetected in skin and follicles of pigment-depositing feather buds, as well as in beaks and tarsi, including those of the red-billed quelea. In contrast, the hepatic (liver) expression of CYP2J19 was consistently higher (>14-fold) in seven species with C4-ketocarotenoid coloration than in species without (including one red species), an association strongly supported by a phylogenetic comparative analysis. The results suggest a critical role of the candidate ketolase, CYP2J19, in the evolution of red C4-ketocarotenoid colour variation in ploceids. As ancestral state reconstruction suggests that ketocarotenoid coloration has evolved twice in this group (once in Euplectes and once in the Quelea/Foudia clade), we argue that while CYP2J19 has retained its ancestral role in the retina, it has likely been co-opted for red coloration independently in the two lineages, via increased hepatic expression.

Seeing red to being red: conserved genetic mechanism for red cone oil droplets and co-option for red coloration in birds and turtles.

Avian ketocarotenoid pigments occur in both the red retinal oil droplets that contribute to colour vision and bright red coloration used in signalling. Turtles are the only other tetrapods with red retinal oil droplets, and some also display red carotenoid-based coloration. Recently, the CYP2J19 gene was strongly implicated in ketocarotenoid synthesis in birds. Here, we investigate CYP2J19 evolution in relation to colour vision and red coloration in reptiles using genomic and expression data. We show that turtles, but not crocodiles or lepidosaurs, possess a CYP2J19 orthologue, which arose via gene duplication before turtles and archosaurs split, and which is strongly and specifically expressed in the ketocarotenoid-containing retina and red integument. We infer that CYP2J19 initially functioned in colour vision in archelosaurs and conclude that red ketocarotenoid-based coloration evolved independently in birds and turtles via gene regulatory changes of CYP2J19 Our results suggest that red oil droplets contributed to colour vision in dinosaurs and pterosaurs.

Red Carotenoid Coloration in the Zebra Finch Is Controlled by a Cytochrome P450 Gene Cluster.

Bright-red colors in vertebrates are commonly involved in sexual, social, and interspecific signaling [1-8] and are largely produced by ketocarotenoid pigments. In land birds, ketocarotenoids such as astaxanthin are usually metabolically derived via ketolation of dietary yellow carotenoids [9, 10]. However, the molecular basis of this gene-environment mechanism has remained obscure. Here we use the yellowbeak mutation in the zebra finch (Taeniopygia guttata) to investigate the genetic basis of red coloration. Wild-type ketocarotenoids were absent in the beak and tarsus of yellowbeak birds. The yellowbeak mutation mapped to chromosome 8, close to a cluster of cytochrome P450 loci (CYP2J2-like) that are candidates for carotenoid ketolases. The wild-type zebra finch genome was found to have three intact genes in this cluster: CYP2J19A, CYP2J19B, and CYP2J40. In yellowbeak, there are multiple mutations: loss of a complete CYP2J19 gene, a modified remaining CYP2J19 gene (CYP2J19(yb)), and a non-synonymous SNP in CYP2J40. In wild-type birds, CYP2J19 loci are expressed in ketocarotenoid-containing tissues: CYP2J19A only in the retina and CYP2J19B in the beak and tarsus and to a variable extent in the retina. In contrast, expression of CYP2J19(yb) is barely detectable in the beak of yellowbeak birds. CYP2J40 has broad tissue expression and shows no differences between wild-type and yellowbeak. Our results indicate that CYP2J19 genes are strong candidates for the carotenoid ketolase and imply that ketolation occurs in the integument in zebra finches. Since cytochrome P450 enzymes include key detoxification enzymes, our results raise the intriguing possibility that red coloration may be an honest signal of detoxification ability.

Sources of Stem Rust Resistance in Wheat-Alien Introgression Lines.

Stem rust is one of the most devastating diseases of wheat. Widely virulent races of the pathogen in the Ug99 lineage (e.g., TTKSK) are threatening wheat production worldwide; therefore, there is an urgent need to enhance the diversity of resistance genes in the crop. The objectives of this study were to identify new sources of resistance in wheat-alien introgression derivatives from Secale cereale, Leymus mollis, L. racemosus, and Thinopyrum junceiforme, postulate genes conferring the resistance, and verify the postulated genes by use of molecular markers. From seedling tests conducted in the greenhouse, the presence of seven known stem rust resistance genes (Sr7b, Sr8a, Sr9d, Sr10, Sr31, Sr36, and SrSatu) was postulated in the wheat-alien introgression lines. More lines possessed a high level of resistance in the field compared with the number of lines that were resistant at the seedling stage. Three 2R (2D) wheat-rye substitution lines (SLU210, SLU238, and SLU239) seemed likely to possess new genes for resistance to stem rust based on their resistance pattern to 13 different stem rust races but the genes responsible could not be identified. Wheat-rye, wheat-L. racemosus, and wheat-L. mollis substitutions or translocations with single and multiple interchanges of chromosomes, in particular of the B and D chromosomes of wheat, were verified by a combination of genomic in situ hybridization and molecular markers. Thus, the present study identified novel resistance genes originating from different alien introgressions into the wheat genome of the evaluated lines. Such genes may prove useful in enhancing the diversity of stem rust resistance in wheat against widely virulent pathogen races such as those in the Ug99 lineage.

Phenolic compounds in blackcurrant (Ribes nigrum L.) leaves relative to leaf position and harvest date.

Blackcurrant leaves are an essential source of phenolic compounds and this study investigated their variation relative to leaf positions and harvest date. The phenolic content varied between harvest dates, although leaf position on the shoot and interactions also played an important role. The contents of quercetin-malonyl-glucoside, kaempferol-malonyl-glucoside isomer and kaempferol-malonyl-glucoside were higher than that of the other identified phenolic compounds, whereas epigallocatechin was the lowest for all investigated leaf positions and harvest dates. The content of several of the compounds was highest in June, while quercetin-glucoside, kaempferol-glucoside and total phenols, increased towards the end of the season. Leaf position influenced the content of myricetin-malonyl-glucoside, myricetin-malonyl-glucoside isomer, quercetin-malonyl-glucoside and kaempferol-glucoside at the end of the season. Knowledge relating to the influence of ontogenetic and harvest time on the content of specific phenolic compounds might contribute in tailoring functional foods or pharmaceutical products using blackcurrant leaves as natural ingredients.

Contribution of organically grown crops to human health.

An increasing interest in organic agriculture for food production is seen throughout the world and one key reason for this interest is the assumption that organic food consumption is beneficial to public health. The present paper focuses on the background of organic agriculture, important public health related compounds from crop food and variations in the amount of health related compounds in crops. In addition, influence of organic farming on health related compounds, on pesticide residues and heavy metals in crops, and relations between organic food and health biomarkers as well as in vitro studies are also the focus of the present paper. Nutritionally beneficial compounds of highest relevance for public health were micronutrients, especially Fe and Zn, and bioactive compounds such as carotenoids (including pro-vitamin A compounds), tocopherols (including vitamin E) and phenolic compounds. Extremely large variations in the contents of these compounds were seen, depending on genotype, climate, environment, farming conditions, harvest time, and part of the crop. Highest amounts seen were related to the choice of genotype and were also increased by genetic modification of the crop. Organic cultivation did not influence the content of most of the nutritional beneficial compounds, except the phenolic compounds that were increased with the amounts of pathogens. However, higher amounts of pesticide residues and in many cases also of heavy metals were seen in the conventionally produced crops compared to the organic ones. Animal studies as well as in vitro studies showed a clear indication of a beneficial effect of organic food/extracts as compared to conventional ones. Thus, consumption of organic food seems to be positive from a public health point of view, although the reasons are unclear, and synergistic effects between various constituents within the food are likely.

Phenols and ascorbic acid in black currants (Ribes nigrum L.): variation due to genotype, location, and year.

Black currant berries contain many biochemical compounds with proven or potential human health benefits. We studied the content of total and single polyphenols, ascorbic acid, soluble sugars, and titratable acidity for two advanced selections and three cultivars of black currant at two distant locations in Sweden (south: 56°06'N; north: 65°21'N) over a 3 year period. Regression analyses revealed the effect of genotype to be considerably larger than that of location and year. However, significant effects of location, year, and interactions were also revealed. A principal component analysis nevertheless separated the genotypes. The content of ascorbic acid, total phenols, total anthocyanins, and soluble sugars was highest in berries from the south, whereas the content of phenolic acids and titratable acidity was highest in berries from the north. The results show that selection of cultivars and production sites are important for cultivation of high-quality black currant raw material for health-promoting products.

An optimized method for analysis of phenolic compounds in buds, leaves, and fruits of black currant ( Ribes nigrum L.).

Although the fruits are the economic driver for the black currant industry, the buds and leaves are excellent sources of beneficial phenolic compounds that may contribute to the future value of the crop. In this study, extraction of phenolic compounds for different parts of the black currant plant was optimized, and an efficient method for their separation by HPLC was developed. This allowed the simultaneous quantification of a range of hydroxycinnamic acids, flavan-3-ols, flavonols, and anthocyanins by DAD following their identification by HPLC-ESI-MS(n). A total of 23 compounds were detected in the buds, 22 of which were found in fruit and leaves. To the best of our knowledge, this is the first report of flavonol glycosides of quercetin, myricetin, isorhamnetin, and kaempferol along with hydroxycinnamic acids such as neo-chlorogenic acid and chlorogenic acid in the buds. Additionally, we provide the first evidence of kaempferol-3-O-rutinoside in black currant leaves. This approach offers avenues for superior combined compositional identification and cultivar selection targeted at the generation of polyphenol-rich products derived from the whole crop and not just the fruit.

A phylogenetic comparative method for studying multivariate adaptation.

Phylogenetic comparative methods have been limited in the way they model adaptation. Although some progress has been made, there are still no methods that can fully account for coadaptation between traits. Based on Ornstein-Uhlenbeck (OU) models of adaptive evolution, we present a method, with R implementation, in which multiple traits evolve both in response to each other and, as in previous OU models, to fixed or randomly evolving predictor variables. We present the interpretation of the model parameters in terms of evolutionary and optimal regressions enabling the study of allometric and adaptive relationships between traits. To illustrate the method we reanalyze a data set of antler and body-size evolution in deer (Cervidae).

Tocopherols in rose hips (Rosa spp.) during ripening.

BACKGROUND: Rose hips are used as a food ingredient and in health products. They are rich in various bioactive compounds such as carotenoids and vitamin C, but data on their vitamin E content (tocopherols and tocotrienols) are limited. In this study, four different species of Rosa were analysed for tocopherol and tocotrienol content during ripening in three different years. RESULTS: Only α- and γ-tocopherol were found in the fleshy parts of the rose hips, and the tocopherol content and vitamin E activity varied depending on date of harvesting, species and year. The amount of vitamin E activity differed between species of Rosa and years, whereas the changes during ripening were relatively small. CONCLUSION: The choice of species must be considered if tocopherol content is to be optimised when rose hips are used as a food ingredient.

Volatile rapid sequence induction in morbidly obese patients.

BACKGROUND AND OBJECTIVE: The interest in bariatric surgery is growing. Morbidly obese patients have an increased risk of hypoxia and decreased blood pressure during rapid sequence induction (RSI). Alternate RSI methods that provide cardiovascular and respiratory stability are required. With this in mind, we evaluated a method for volatile RSI in morbidly obese patients. DESIGN: Observational study. METHODS: Thirty-four patients with mean BMI 42.4 kg m undergoing bariatric surgery (morbidly obese group) and 22 patients with mean BMI 25.6 kg m as a control group were included in the study. Anaesthesia was induced with sevoflurane, propofol, suxamethonium and alfentanil, designed to avoid respiratory and haemodynamic adverse events and to minimise depressing effect on the brain respiratory centre under ongoing RSI. Peripheral oxygen saturation (SpO2) and mean arterial blood pressure were registered before and after endotracheal intubation. In addition, two time periods were measured during RSI: spontaneous breathing time (SBT) and apnoea time. RESULTS: We found no significant differences between the groups. No periods of desaturation were detected. SpO2 was 100% before and after endotracheal intubation in all patients. Mean arterial pressure was maintained at a stable level in both groups. Mean SBT and apnoea time were 65.6 and 45.8 s in the morbidly obese group, and 70.7 and 47.7 s in the control group, respectively. CONCLUSION: A combination of sevoflurane, propofol, suxamethonium and alfentanil is a suitable method for RSI which maintains cardiovascular and respiratory stability in both morbidly obese and lean patients.

UV-deprived coloration reduces success in mate acquisition in male sand lizards (Lacerta agilis).

BACKGROUND: Recent work on animal signals has revealed a wide occurrence of UV signals in tetrapods, in particular birds, but also in lizards (and perhaps other Squamate reptiles). Our previous work on the Swedish sand lizard (Lacerta agilis) has verified, both in correlative selection analyses in the wild and with laboratory and field experiments, the importance of the green 'badge' on the body sides of adult males for securing mating opportunities, probably mostly through deterring rival males rather than attracting females. The role of UV in communication has, however, never been examined. METHODOLOGY/PRINCIPAL FINDINGS: Here we show that when measured immediately after spring skin shedding, there is also signaling in the UV. By UV-depriving the signal (reflectance) with sun block chemicals fixated with permeable, harmless spray dressing, we show that males in the control group (spray dressing only) had significantly higher success in mate acquisition than UV-deprived males. CONCLUSIONS/SIGNIFICANCE: These results suggest that at least two colour traits in sand lizards, badge area and UV, contribute to rival deterrence and/or female choice on UV characters, which elevates success in mate acquisition in UV intact male sand lizards.

General practitioners' reasoning about using mobile distance-spanning technology in home care and in nursing home care.

The trend for health care and nursing care turns from hospital to health care and nursing care at home. Studies have shown that health care professionals have no access to patient records in home and nursing home settings. Technological development creates opportunities for a host of mobile technology solutions. The aim of this study was to describe the reasoning among general practitioners (GPs) about the use of mobile distance-spanning technology (MDST) in care at home and in nursing homes. Seventeen GPs were divided in five groups for a group interview. The interviews were tape-recorded and transcribed verbatim. The qualitative content analysis resulted in four areas about the MDST, MDST has an impact on GPs' work, the nurses' profession, and the patient and the family, with nine adherent categories. The findings were interpreted and formulated in the theme: MDST should be used with caution. The results show quite a few expressions about the MDST as useful and valuable in health care at home and in nursing home settings; however, in every category, there were text that we interpreted as caution when using the MDST. The MDST cannot be used in all situations and cannot replace human meetings in health care and nursing care at home and in nursing homes. The MDST should primarily be a tool for the profession, and understanding the professions' reasoning about technology use in health care at home and in nursing home settings must be the base for implementing MDST.

Convergent evolution of red carotenoid coloration in widowbirds and bishops (Euplectes spp.).

Avian carotenoid-based signals are classic examples of sexually selected, condition-dependent threat displays or mate choice cues. In many species, male dominance or mating success is associated with redder (i.e., longer wavelength) color hues, suggesting that red colors are either more efficient or more reliable signals than yellow colors. Few studies, however, have investigated selection for redness in a macroevolutionary context. Here, we phylogenetically reconstruct the evolution of carotenoid coloration in the African widowbirds and bishops (Euplectes spp.), for which agonistic selection for redder hues, as well as pigmentary mechanisms, is well documented. Using reflectance spectrometry for objective color quantification, and accounting for phylogenetic uncertainty, we find that yellow plumage color is a retained ancestral state in Euplectes, and that red color hues have convergently evolved two or three times. Results are discussed in relation to a known diversity in pigment mechanisms, supporting independent origins of red color, and suggesting that agonistic selection and physiological constraints have interacted to generate color diversity in Euplectes.

Differential ability of carotenoid C4-oxygenation in yellow and red bishop species (Euplectes spp.).

Male breeding plumages of African widowbirds and bishops (Euplectes spp.) show striking variation in carotenoid-based plumage coloration, with saturated yellow or orange-red patches of different size. Yet, from observations and experiments, agonistic signaling appears to have been a generalized sexual selection pressure for redness in the genus. Recent results show that yellow and red widowbird colors derive from distinctly different pigment profiles, and suggest that species vary in their ability to metabolize ingested carotenoids. We used reflectance spectrometry and High Performance Liquid Chromatography (HPLC) to describe the species-specific colors and plumage carotenoids of the congeneric yellow-crowned bishop (E. afer) and southern red bishop (E. orix). Results show that the yellow rump color of E. afer primarily derives from direct-deposited, dietary yellow pigments, i.e. lutein and zeaxanthin. In the red breast of E. orix, these are complemented by smaller amounts of derived red C4-keto-carotenoids: mainly alpha-doradexanthin, but also beta-doradexanthin, canthaxanthin, astaxanthin and adonirubin. We also performed a diet supplementation experiment to investigate the relative importance of nutritional and metabolic constraints in determining the differential occurrence of C4-keto-carotenoids, and thus red plumage color, in the two species. Our results indicate that E. orix, but not E. afer, can manufacture red C4-keto-carotenoids (alpha-doradexanthin and canthaxanthin) from yellow dietary precursors (lutein and beta-carotene).