BUSCADOR RECOLECTA

Sexual selection promotes the evolution of conspicuous animal ornaments. To evolve as signals, these traits must reliably express the “quality” of the bearer, an indicator of individual fitness. Direct estimates of individual fitness may include the contribution of longevity and fecundity. However, evidence of a correlation between the level of signal expression and these two fitness components are scarce, at least among vertebrates. Relative fitness is difficult to assess in the wild as age at death and extra-pair paternity rates are often unknown. Here, in captive male red-legged partridges, we show that carotenoid-based ornament expression, i.e., redness of the bill and eye rings, at the beginning of reproductive life predicts both longevity (1–7 years) and lifetime breeding output (offspring number and hatching success). The recently proposed link between the individual capacity to produce red (keto) carotenoid pigments and the efficiency of cell respiration could, ultimately, explain the correlation with lifespan and, indirectly, fecundity. Nonetheless, in males of avian species, carotenoid-based coloration in bare parts is also partially controlled by testosterone. We also manipulated androgen levels throughout life by treating males with testosterone or antiandrogen compounds. Treatments caused correlations between signal levels and both fitness components to disappear, thus making the signals unreliable. This suggests that the evolution of carotenoid-based sexual signals requires a tightly-controlled steroid metabolism., Financial support was obtained from the projects PII1I09-0271-5037, PII1C09-0128-4724, SBPLY/17/180501/000468 from the JCCM (co-financed with European Regional Development Fund –ERDF), CGL2009-10883-C02-02 from Ministerio de Ciencia e Innovación (MICIN, Spain) and CGL2015-69338-C2-2-P from Ministerio de Economía, Industria y Competitividad (MINECO). AC and LP-R were supported by a “Juan de la Cierva-formación” postdoctoral grant (MINECO, FJCI-2015-23536) and a SECTI postdoctoral contract from the University of Castilla-La Mancha (UCLM), respectively. AC is currently supported by a postdoctoral fellowship from Fundación Ramón Areces., Peer reviewed

Dataset (excel) containing the data used in the analyses of the accepted manuscript entitled: Testing the shared-pathway hypothesis in the carotenoid-based coloration of red crossbills. The article will be published in Evolution., Descriptions of each variable are included as comments on the name of the variable (first row). Readme file added., This is a dataset that allowed testing the shared-pathway hypothesis on the honest signaling based on animal colorations created by red ketocarotenoid pigments. The dataset includes levels of pigments and vitamins in blood and feathers as well as feather coloration in captive Eurasian crossbills under captivity., Ministerio de Economía y Competitividad, Ministerio de Ciencia e Innovación, Fundación Ramón Areces, Spain., No

Descriptions of each variable are included as comments on the name of the variable (first row). Readme file added., This is a dataset that allows testing the effect of a mito-targeted antioxidant (mitoTEMPO) and a thyroid hormone (T3) on the level of expression of the gene CYP2J19 in the bill tissue of male zebra finches, and also their impact on bill redness and circulating carotenoid levels., Ministerio de Economía y Competitividad, Ministerio de Ciencia e Innovación, Fundación Ramón Areces, Spain., Peer reviewed

Sexual steroids can play an important role as life-history organizers. In males, high circulating testosterone levels induce physiological/behavioral costs and benefits, leading to trade-offs. However, studies simultaneously testing the impact of these levels in both fitness components (survival and fecundity) during lifetime are scarce and limited to wild birds. To determine the mortality causes or hormonal manipulation impacts on male fertility is, nonetheless, a difficult task in free-ranging animals that could be easier in captivity. We longitudinally monitored captive red-legged partridges (Alectoris rufa) and exposed males to high exogenous testosterone levels, anti-androgens, or a control treatment during each breeding period throughout their lives. Theory predicts that individuals maintaining high androgen levels should obtain higher fitness returns via reproduction, but suffer reduced longevity. Testosterone-treated male partridges, accordingly, lived shorter compared to controls, since they were more prone to die from a natural bacterial infection. However, the same birds seemed to have a lower capacity to fertilize eggs, probably due to endocrine feedback reducing testicular mass. These results show that exogenous testosterone can exert unpredicted effects on fitness parameters. Therefore, caution must be taken when drawing conclusions from non-fully controlled experiments in the wild. Males treated with the androgen-receptor blocker flutamide did not outlive controls as predicted by the life-history trade-off theory, but their mates laid eggs with higher hatching success. The latter could be due to mechanisms improving sperm quality/quantity or influencing maternal investment in egg quality. Testosterone receptor activity/amount could thus be as relevant to fitness as testosterone levels., Open access funding provided by University of Turku (UTU) including Turku University Central Hospital. Financial support was obtained from the projects PII1I09-0271-5037, PII1C09-0128-4724, SBPLY/17/180501/000468 from the JCCM (co-financed with European Regional Development Fund-ERDF), CGL2009-10883-C02-02 from Ministerio de Ciencia e Innovación (MICIN, Spain), CGL2015-69338-C2-2-P from Ministerio de Economía, Industria y Competitividad (MINECO), and PID2019-109303GB-I00 from MICIN. AC and LP-R were supported by a “Juan de la Cierva-formación” postdoctoral grant (MINECO, FJCI-2015-23536) and a SECTI postdoctoral contract from the University of Castilla-La Mancha (UCLM), respectively. AC is currently supported by a postdoctoral fellowship from Fundación Ramón Areces. AAR-H is funded by a Marie Skłodowska-Curie grant (agreement 842085)., Peer reviewed

The mechanisms involved in the production of red carotenoid‐based ornaments of vertebrates are still poorly understood. These colorations often depend on enzymatic transformations (ketolation) of dietary yellow carotenoids, which could occur in the inner mitochondrial membrane (IMM). Thus, carotenoid ketolation and cell respiration could share biochemical pathways, favoring the evolution of ketocarotenoid‐based ornaments as reliable indices of individual quality under sexual selection. Captive male red crossbills (Loxia curvirostra Linnaeus) were exposed to redox‐active compounds designed to penetrate and act in the IMM: an ubiquinone (mitoQ) or a superoxide dismutase mimetic (mitoTEMPO). MitoQ can act as an antioxidant but also distort the IMM structure, increasing mitochondrial free radical production. MitoQ decreased yellow carotenoids and tocopherol levels in blood, perhaps by being consumed as antioxidants. Contrarily, mitoTEMPO‐treated birds rose circulating levels of the second most abundant ketocarotenoid in crossbills (i.e., canthaxanthin). It also increased feather total red ketocarotenoid concentration and redness, but only among those birds exhibiting a redder plumage at the start of the study, that is, supposedly high‐quality individuals. The fact that mitoTEMPO effects depended on original plumage color suggests that the red‐ketocarotenoid‐based ornaments indicate individual quality as mitochondrial function efficiency. The findings would thus support the shared pathway hypothesis., A.C. is supported by a postdoctoral fellowship from Fundación Ramón Areces. Financial support was obtained from the projects CGL2015‐69338‐C2‐2‐P and PID2019‐109303GB‐I00 from Ministerio de Economía, Industria y Competitividad (MINECO) and Ministerio de Ciencia e Innovación (MICINN), respectively (Spanish Government)., Peer reviewed

Financial support was obtained from projects CGL-2009-10883-C02-02, CGL2012-40229-C02-01 and CGL2015-69338-C2-2-P and PID2019-109303GB-I00 from Ministerio de Economía y Competitividad, MINECO, Spanish Government., Peer reviewed

[EN] Telomeres are repetitive DNA sequences at the end of chromosomes that protect them from degradation. They have been the focus of intense research because short telomeres would predict accelerated ageing and reduced longevity in vertebrates. Oxidative stress is considered a physiological driver of the telomere shortening and, consequently, short lifespan. Among molecules fighting against oxidative stress, glutathione is involved in many antioxidant pathways. Literature supports that oxidative stress may trigger a compensatory “hormetic” response increasing glutathione levels and telomere length. Here, we tested the link between total glutathione concentration and telomere length in captive birds (zebra finches; Taeniopygia guttata). Total glutathione levels were experimentally decreased during birds’ growth using a specific inhibitor of glutathione synthesis (buthionine sulfoximine; BSO). We monitored the birds’ reproductive performance in an outdoor aviary during the first month of life, and their longevity for almost 9 years. Among control individuals, erythrocyte glutathione levels during development positively predicted erythrocyte telomere length in adulthood. However, BSO-treated females, but not males, showed longer telomeres than control females in adulthood. This counterintuitive finding suggests that females mounted a compensatory response. Such compensation agrees with precedent findings in the same population where the BSO treatment increased growth and adult body mass in females but not males. BSO did not influence longevity or reproductive output in any sex. However, early glutathione levels and adult telomere length interactively predicted longevity only among control females. Those females with “naturally” low (non-manipulated) glutathione levels at the nestling age but capable of producing longer telomeres in adulthood seem to live longer. The results suggest that the capability to mount a hormetic response triggered by low early glutathione levels can improve fitness via telomere length. Overall, the results may indicate a sex-specific link between glutathione and telomere values. Telomerase activity and sexual steroids (estrogens) are good candidates to explain the sex-biased mechanism underlying the early-life impact of oxidative stress on adult telomere length., [ES] Los telómeros son secuencias repetitivas de ADN que se encuentran al final de los cromosomas protegiéndolos de la degradación. Los telómeros han sido foco de intensa investigación ya que tener telómeros cortos predice un envejecimiento acelerado y una longevidad reducida en vertebrados. El estrés oxidativo se considera causante del acortamiento de los telómeros y, consecuentemente, una corta esperanza de vida. Entre las moléculas que luchan contra el estrés oxidativo, el glutatión está relacionado con numerosas vías metabólicas de otros antioxidantes. La literatura defiende que el estrés oxidativo podría desencadenar una respuesta hormética compensatoria, aumentando los niveles de glutatión y la longitud de los telómeros. En este trabajo testamos la relación entre los niveles de glutatión y la longitud de los telómeros en aves en condiciones de cautividad (diamantes mandarines; Taeniopygia guttata). Los niveles de glutatión fueron reducidos experimentalmente durante el desarrollo de las aves usando un inhibidor específico de la síntesis de glutatión (Buthionina sufolximina; BSO). El desempeño reproductivo de estas aves fue monitoreado en un aviario exterior durante los primeros meses de vida y la longevidad durante casi nueve años. Entre los individuos controles, los niveles de glutatión durante el desarrollo predijeron positivamente la longitud de los telómeros a edad adulta. Sin embargo, las hembras tratadas con BSO, pero no los machos, mostraron telómeros más largos a edad adulta que las hembras controles. Este hallazgo aparentemente contradictorio sugiere que las hembras desarrollaron una respuesta compensatoria. Tal compensación concuerda con los hallazgos anteriores obtenidos en la misma población: las hembras tratadas con BSO vieron aumentado su peso corporal a edad adulta, resultado no encontrado entre los machos. El tratamiento con BSO no afectó la longevidad o el desempeño reproductivo de ningún sexo. Sin embargo, los niveles de glutatión durante el desarrollo y la longitud de los telómeros a edad adulta predijeron interactivamente la longevidad de las hembras controles. Aquellas hembras con niveles bajos “naturales” (no manipulados) de glutatión cuando eran pollos pero que pudieron producir telómeros más largos a edad adulta vivieron más. Este resultado sugiere que la capacidad de desarrollar una respuesta hormética desencadenada por niveles bajos de glutatión durante el desarrollo puede mejorar la eficacia biológica a través de la longitud de los telómeros. De manera general, los resultados indicarían una relación específica del sexo entre los valores de glutatión y de telómeros. La actividad de la enzima telomerasa y los esteroides sexuales (estrógenos) son buenos candidatos para explicar este mecanismo dependiente del sexo que impulsa el impacto del estrés oxidativo sufrido durante el desarrollo en la longitud de los telómeros de adultos., A.A.R.-H. was funded by a Formación de Personal de Investigación grant [BES-2010-035013; Ministerio de Economía y Competitividad, MINECO, Spanish Government] and was supported by the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska‐Curie grant agreement [842085] and by a postdoctoral contract María Zambrano (University of Castilla-La Mancha) from the Program of Requalification of the Spanish University System (Spanish Ministry of Universities) financed by the European Union—NextGenerationEU. Financial support was obtained from projects [CGL-2009-10883-C02-02, CGL2012-40229-C02-01 and CGL2015-69338-C2-2-P, and PID2019-109303GB-I00] from MINECO, (Spain)., Peer reviewed

Colorful ornaments have been the focus of sexual selection studies since the work of Darwin. Yellow to red coloration is often produced by carotenoid pigments. Different hypotheses have been formulated to explain the evolution of these traits as signals of individual quality. Many of these hypotheses involve the existence of a signal production cost. The carotenoids necessary for signaling can only be obtained from food. In this line, carotenoid-based signals could reveal an individual's capacity to find sufficient dietary pigments. However, the ingested carotenoids are often yellow and became transformed by the organism to produce pigments of more intense color (red ketocarotenoids). Biotransformation should involve oxidation reactions, although the exact mechanism is poorly known. We tested the hypothesis that carotenoid biotransformation could be costly because a certain level of oxidative stress is required to correctly perform the conversion. The carotenoid-based signals could thus reveal the efficiency of the owner in successfully managing this challenge. In a bird with ketocarotenoid-based ornaments (the red-legged partridge Alectoris rufa), the availability of different carotenoids in the diet (i.e. astaxanthin, zeaxanthin and lutein) and oxidative stress were manipulated. The carotenoid composition was analyzed and quantified in the ornaments, blood, liver and fat. A number of oxidative stress biomarkers were also measured in the same tissues. First, we found that color and pigment levels in the ornaments depended on food levels of those carotenoids used as substrates in biotransformation. Second, we found that birds exposed to mild levels of a free radical generator (diquat) developed redder bills and deposited higher amounts of ketocarotenoids (astaxanthin) in ornaments. Moreover, the same diquat-exposed birds also showed a weaker resistance to hemolysis when their erythrocytes were exposed to free radicals, with females also enduring higher oxidative damage in plasma lipids. Thus, higher color production would be linked to higher oxidative stress, supporting the biotransformation hypothesis. The recent discovery of an avian oxygenase enzyme involved in converting yellow to red carotenoids may support our results. Nonetheless, the effect could also depend on the abundance of specific substrate carotenoids in the diet. Birds fed with proportionally higher levels of zeaxanthin showed the reddest ornaments with the highest astaxanthin concentrations. Moreover, these birds tended to show the strongest diquat-mediated effect. Therefore, in the evolution of carotenoid-based sexual signals, a biotransformation cost derived from maintaining a well-adjusted redox machinery could coexist with a cost linked to carotenoid acquisition and allocation (i.e. a resource allocation trade-off)., Esther García-de Blas was supported by a predoctoral grant (JAE-PRE) from the Consejo Superior de Investigaciones Científicas (CSIC) co-financed by Fondo Social
Europeo (EU). This study was funded by Consejería de Educación y Ciencia, Junta de
Comunidades de Castilla la Mancha (project ref.: PII1I09-0271-5037) and Ministerio de
Economía y Competitividad (CGL2009-10883-C02-02 and CGL2015-69338-C2-2-P)
from the Spanish Government., Peer Reviewed

In the early 2000s, a new component of the cost of reproduction was proposed: oxidative stress. Since then the oxidative cost of reproduction hypothesis has, however, received mixed support. Different arguments have been provided to explain this. Among them, the lack of a life-history perspective on most experimental tests was suggested. We manipulated the levels of a key intracellular antioxidant (glutathione) in captive zebra finches (Taeniopygia guttata) during a short period of early life and subsequently tested the oxidative cost of reproduction. Birds were allowed to mate freely in an outdoor aviary for several months. We repeatedly enlarged or reduced their broods to increase or reduce, respectively, breeding effort. Birds whose glutathione levels were reduced during growth showed higher erythrocyte resistance to free radical-induced haemolysis when forced to rear enlarged broods. This supports the hypothesis predicting the occurrence of developing programmes matching early and adult environmental conditions to improve fitness. Moreover, adult males rearing enlarged broods endured higher plasma levels of lipid oxidative damage than control males, whereas adult females showed the opposite trend. As most previous studies reporting non-significant or opposite results used females only, we also discuss some sex-related particularities that may contribute to explain unexpected results., A.A.R.-H. was funded by a Formación de Personal de Investigación grant (BES-2010-035013; Ministerio de Economía y Competitividad, MINECO, Spanish Government). Financial support was obtained from projects CGL-2009-10883-C02-02, CGL2012-40229-C02-01 and CGL2015-69338-C2-2-P (MINECO, Spain)., Peer Reviewed

Pheomelanin is a sulphur-containing yellow-to-reddish pigment whose synthesis consumes the main intracellular antioxidant (glutathione; GSH) and its precursor cysteine. Cysteine used for pheomelanogenesis cannot be used for antioxidant protection. We tested whether the expression of Slc7a11, the gene regulating the transport of cysteine to melanocytes for pheomelanogenesis, is environmentally influenced when cysteine/GSH are most required for antioxidant protection. We found that zebra finches Taeniopygia guttata developing pheomelanin-pigmented feathers during a 12-day exposure to the pro-oxidant diquat dibromide downregulated the expression of Slc7a11 in feather melanocytes, but not the expression of other genes that affect pheomelanogenesis by mechanisms different from cysteine transport such as MC1R and Slc45a2. Accordingly, diquat-treated birds did not suffer increased oxidative stress. This indicates that some animals have evolved an adaptive epigenetic lability that avoids damage derived from pheomelanogenesis. This mechanism should be explored in human Slc7a11 to help combat some cancer types related to cysteine consumption., Financial support was obtained from a Investigador FCT Fellowship (ref. IF/00870/2012/CP0189/CT0009) from the Portuguese Foundation for Science and Technology and by a Ramón y Cajal Fellowship (ref. RYC-2012-10237) from the Spanish Ministry of Economy and Competitiveness (MINECO) to I.G., and from the projects CGL2012-40229-C02-01 and CGL2015-69338-C2-2-P, both from MINECO, to C.A.A., Peer Reviewed

The evolution of honest animal communication is mostly understood through the handicap principle, which is intrinsically dependent on the concept of individual quality: low-quality individuals are prevented from producing high-quality signals because, if they did so, they would pay greater production costs than high-quality individuals. We tested an alternative explanation for the black bib size of male house sparrows, Passer domesticus, an honest signal of quality the expression of which is negatively related to levels of the pigment pheomelanin in the constituent feathers. We previously showed that experimental depletion of cysteine, which participates in pheomelanogenesis, improves the phenotype (bibs larger than in controls) of high-quality males (birds with largest bibs initially) only. Here, we conducted an experiment under opposite conditions, increasing the availability of dietary cysteine, and obtained opposite results: deteriorated phenotypes (bibs smaller than in controls) were only expressed by high-quality birds. Some birds were also treated with the pro-oxidant diquat dibromide, and we found that the cellular resistance to free radicals of high-quality birds benefited more from the antioxidant activity of cysteine against diquat than that of lowquality birds. These findings support the existence of a mechanism uncoupling cysteine and pheomelanin in low-quality birds that confers on them a low sensitivity to variations in cysteine availability. This constitutes an explanation for the evolution of signal honesty that overcomes the limitations of the handicap principle, because it provides a specific definition of individual quality and because costs are no longer required to prevent low-quality individuals from producing large signals., I.G. was supported by a Marie Curie Intra-European Fellowship (PIEF-GA-2009-252145) within the Seventh Framework Programme and, during writing, by a Ramón y Cajal Fellowship (RYC-2012-10237) from the Ministerio de Economı́a y Competitividad (MINECO). Laboratory analyses were funded by Ministerio de Ciencia e Innovación (CGL2009-10883-C02-02 and CGL2015-69338-C2-2-P)., Peer Reviewed

Excel Dataset including "initial" and "final" values for red coloration, plasma carotenoids and vitamins of partridges treated with diquat or control (diquat row) and receiving different carotenoids in the diet (group). The dataset also includes values from terminal tissue samples (ornaments, liver, heart and fat) and the carotenoid and vitamin content in the egg yolk. Finally, it also includes initial values as residuals from mixed models controlling for random factors (e.g. lab session) and confounding covariates (red chip hue in leg pictures). These residuals were used as covariates in model testing experimental treatment effects on final values., Esther García-de Blas was supported by a predoctoral grant (JAE-PRE) from the Consejo Superior de Investigaciones Científicas (CSIC) co-financed by Fondo Social Europeo (EU). This study was funded by Consejería de Educación y Ciencia, Junta de Comunidades de Castilla la Mancha (project ref.: PII1I09-0271-5037) and Ministerio de Economía y Competitividad (CGL2009-10883-C02-02 and CGL2015-69338-C2-2-P) from the Spanish Government., No

The role of reproduction in increasing oxidative stress may be fundamental to understanding aging and the evolutionary trade-off between survival and fecundity. However, contradictory results among experimental studies have challenged the oxidative cost of reproduction. Limitations in experimental design may explain inconsistent findings. Nonetheless, some authors have argued that the hypothesis is founded on the faulty assumptions of an energy-based allocation trade-off and a direct positive link between metabolic rates and the production of reactive oxygen species (ROS) by the mitochondria. We propose that evolutionary trade-offs do not require the allocation of limiting resources and that reproduction may result in ROS-induced oxidative stress without increased mitochondrial ROS. We discuss the previously published oxidative-shielding hypothesis and propose two new hypotheses: hormesis and extortion for reproduction. These hypotheses aim to explain the counterintuitive results indicating that there is less oxidative damage in animals allowed to breed compared with those prevented from reproducing., Ana Angela Romero-Haro was funded by a Formación de Personal de Investigación grant (no. BES-2010-035013; Ministerio de Economía y Competitividad, MINECO, Spanish Government) and project nos. CGL2012-40229-C02-01 and CGL2015-69338-C2-2-P (MINECO, Spain)., Peer Reviewed

Carotenoids give color to conspicuous animal signals that are often the product of sexual selection. Knowledge of the mechanisms involved in carotenoid-based signaling is critical to understanding how these traits evolve. However, these mechanisms remain only partially understood. Carotenoids are usually viewed as scarce dietary antioxidants whose allocation to ornaments may trade off against health. This trade-off would ensure its reliability as a signal of individual quality. In the case of red (keto)carotenoids, the literature suggests that some species may show constraints in their uptake. Canthaxanthin is one of the most common ketocarotenoids in red ornaments of animals. It is often commercially used as a dietary supplement to obtain redder birds (e.g. poultry). We increased the dietary canthaxanthin levels in captive red-legged partridges (Alectoris rufa). This species shows red non-feathered parts mostly pigmented by another common ketocarotenoid: astaxanthin. We studied the impact on the uptake of carotenoids and vitamins and, finally, on coloration. We also tested the potential protective effect of canthaxanthin when exposing birds to a free radical generator (diquat). Canthaxanthin did not apparently protect birds from oxidative stress, but interfered with the absorption of yellow carotenoids (lutein and zeaxanthin). Zeaxanthin is a precursor of astaxanthin in enzymatic pathways, and their levels in tissues and eggs were lower in canthaxanthin-supplied birds. This led to lower astaxanthin levels in ornaments and paler coloration. As far as we know, this is the first report of a carotenoid supplementation decreasing animal coloration. The results have implications for understanding carotenoid-based signaling evolution, but also for improving husbandry/experimental procedures., E.G.-d.B. was supported by a predoctoral grant (JAE-PRE) from the Consejo Superior de Investigaciones Cientıficas (CSIC) co-financed by Fondo Social Europeo (EU). This study was funded by Consejerıa de Educacion y Ciencia, Junta de Comunidades de Castilla la Mancha (project ref.: PII1I09-0271-5037) and Ministerio de Economıa y Competitividad (CGL2009-10883-C02-02 and CGL2015-69338-C2-2-P) from the Spanish Government., Peer reviewed, Peer Reviewed

Dataset of the scientific article "Carotenoid-based coloration predicts both longevity and lifetime fecundity in male birds, but testosterone disrupts signal reliability"., Financial support was obtained from the projects PII1I09-0271-5037, PII1C09-0128-4724, SBPLY/17/180501/000468 from the JCCM (co-financed with European Regional Development Fund –ERDF) and CGL2009-10883-C02-02 and CGL2015-69338-C2-2-P from Ministerio de Ciencia e Innovación (MICIN, Spain). AC and LP-R were supported by a “Juan de la Cierva-formación” postdoctoral grant from Ministerio de Economía, Industria y Competitividad (MINECO, FJCI-2015-23536) and a SECTI postdoctoral contract from the University of Castilla-La Mancha (UCLM), respectively., Peer reviewed