Expression Of Secondary Sexual Characters Research Articles

Development of a Simple Morphometric Model to Identify Sex in Chinook Salmon Returning to Spawn in the Yukon River

AbstractChinook Salmon Oncorhynchus tshawytscha support major fisheries in the Yukon River in Canada and the United States. Demographic data, including length, age, and sex composition of annual runs underpin management programs tasked with meeting escapement goals and providing for various fisheries within the drainage. Numerous sampling projects along the river collect these data annually, most without sacrificing fish. However, substantial error can occur when assigning sex based on observations of secondary sexual characteristics, particularly early in the spawning migration. We sought to develop a quantitative method of analyzing morphology of Chinook Salmon in the Yukon River that would achieve ≥95% accuracy of sex assignment with live fish. We collected snout lengths (SL) and mid‐eye‐to‐fork lengths (MEF) from 2,342 known‐sex fish from six regions of the drainage ranging from 40 to 2,000 km upstream from the sea, including a collection from postspawning fish. We fit three logistic regression models to the data using MEF, the ratio of SL to MEF, and regional group as covariates, including interactions and quadratic terms. Model selection was made using Akaike information criterion and cross‐validation of prediction performance. Accuracy rates of the final quantitative model ranged from 79% for a lower Yukon River group to 92% for the postspawning group. Though short of our accuracy goal, the quantitative method may provide an improvement over existing methods of sex assignments in some regions of the drainage. Lower assignment rates in the lower river may reflect the mixed‐stock composition of the fishery, where samples include fish with both short and long migrations ahead of them. However, we speculate that Chinook Salmon migrating to upper Yukon River spawning areas minimize the expression of secondary sexual characteristics, such as SL in males, and instead allocate their energy reserves to accomplishing the long migrations.

Somatotypical features of the age dynamics of secondary sexual characteristics and functional parameters in city schoolchildren

Objective:to assess the constitutional features of the age dynamics of secondary sexual characteristics and functional parameters of city schoolchildren in the age range of 7–17 years.Materials and methods.The objects of the study were schoolchildren aged 7–17. The stages of the expression of secondary sexual characteristics were determined visually according to the scheme by J.M. Tanner. The functional parameters of the examined schoolchildren were assessed using the methods of dynamometry, spirometry; blood pressure and heart rates, as well as the time of simple sensorimotor reactions were measured.Results.As a result of the performed studies, it has been found that representatives of the hypersomnic types are ahead of other types to reveal the first stages of secondary sexual characteristics. Schoolchildren with the leptosomic morphotypes due to higher rates of their development have reached the definitive stages by the same age as those with the hypersomnic variants. The intensity of age-related changes in functional parameters (strength qualities, circulatory and respiratory systems, nervous system) in the studied objects depends on their body type.Conclusion.The stage and rate of puberty, as well as the development of functional parameters in city schoolchildren depends on their somatotype.

Diagnóstico radiológico del síndrome de interrupción del tallo hipofisario Neurohipófisis ectópica

Pituitary stalk disruption syndrome is a congenital anomaly characterized by neuroradiologic demonstration of an absent, interrupted, or hypoplastic pituitary stalk, aplastic/hypoplastic adenohypophysis, and ectopic neurohypophysis. This syndrome has been related to severe forms of congenital hypopituitarism, associated with multiple deficiencies of pituitary hormones. Perinatal signs and symptoms presented by patients include hypoglycemia in up to 61%, jaundice in 38%, micropenis in 77% and cholestasis in 19%, neonatal seizures occurred in 75% of children. During childhood, they tend to have short stature and a decrease in growth speed, as well as a delay in the expression of secondary sexual characteristics. In our clinical case, an adolescent patient was presented whose main clinical manifestations were delayed secondary sexual characteristics, the main findings were found in nuclear magnetic resonance, including absence of the pituitary stalk, ectopic neurohypophysis, located adjacent to the tuber cinereum and hypoplastic adenohypophys. Keywords: Sella turcica; pituitary stalk; neurohypophysis; adenohypophysis; hyperintense; magnetic resonance imaging

Parasitism affects variation in a male damselfly sexual ornament

Sexually selected ornaments in animals are costly, with parasitism often affecting the degree to which they are expressed. Male Calopteryx splendens damselflies exhibit melanised ‘wing spots’. Those possessing large spots are favoured by females but also have an increased likelihood of being attacked by Calopteryx virgo, a common sympatric competitor. Melanin is used to produce the wing spots, but it is also used in immune defence against parasites that commonly infect damselflies. A total of 261 C. splendens males were collected from 26 Finnish and Latvian populations, of which half were found to be sympatric with C. virgo. It was found that males which originated from populations in which eugregarine parasites were present had smaller wing spots than individuals from parasite-free populations. Contrary to previous studies, the wing spots of C. splendens males in populations sympatric with C. virgo were not found to be smaller than those in allopatric populations. Parasite presence in C. splendens was found to be strongly associated with populations sympatric with C. virgo. The results suggest that the presence of C. virgo may increase rates of parasitism in C. splendens, and show that parasitism is an important additional factor to interspecific aggression in determining variation in the sizes of the wing spots of C. splendens males. These findings highlight a lack of understanding on the determinants of the expression of secondary sexual characters and the processes of how parasitism affects hosts.

Viability and expression of sexual ornaments in the barn swallow Hirundo rustica: a meta-analysis.

Sexual selection results in the evolution of exaggerated secondary sexual characters that can entail a viability cost. However, in species where sexual ornaments honestly reflect individual quality, the viability cost of secondary sexual characters may be overwhelmed by variation in individual quality, leading to expect that individuals with the largest secondary sexual characters show higher, rather than lower viability. Here, we used meta-analyses to test whether such expected positive relationship between sexual ornamentation and viability exists in the barn swallow Hirundo rustica, which is one of the most studied model species of sexual selection under field conditions. We found a mean positive effect size of viability in relation to the expression of secondary sexual characters of 0.181 (CI: 0.084-0.278), indicating that in this species the more ornamented individuals are more viable, and therefore of high quality. Analyses of moderator variables showed similar effects in males and females, the H.r.rustica subspecies rather than others and tail length rather than other secondary sexual characters. Future research emphasis on other subspecies than the European one and secondary sexual characters than tail length may help identify the sources of heterogeneity in effect sizes.

Steroidogenesis by testis and accessory glands of the Lusitanian toadfish, Halobatrachus didactylus, during reproductive season

In teleost fish sex steroids are essential for gonadal function and have marked effects in reproductive and agonistic behavior and in the expression of secondary sexual characteristics. The Lusitanian toadfish, Halobatrachus didactylus, has two male morphotypes: type I males are territorial nest-holders and have large accessory glands while type II males are smaller, have a relatively large testis and small accessory glands. In the present study, the steroidogenic activity of the testis and accessory testicular glands of the Lusitanian toadfish were examined in vitro as well as their presence in urine. The testis of type I males produced 11-ketotestosterone (11KT) and 11β-hydroxy-4-androstene-3,17-dione (11βA) from tritiated 17-hydroxyprogesterone, while those of type II males produced testosterone (T) and 11β,17β-dihydroxy-4-andosten-3-one (11βT), but not 11KT. Additionally, the testis and accessory glands of both morphs produced mostly 5β,3α-reduced and 17,20α-hydroxylated metabolites. Type I, but not of type II, males synthesised 5β-reduced androgens in their accessory glands. The presence of 11βA exclusively in the urine of type I males during reproductive season suggests an association with maintenance of secondary sexual characteristics and behavior in this morph. The urine of both types of males contained two 5α-androstane and 5β-pregnane glucuronides. Among the latter steroids, those that are 17,21-dihydroxylated are potentially metabolites from cortisol and were found only in type I males during the spawning season. The diversity of metabolites produced by the testis and accessory glands and the presence of some in urine is suggestive of a potential role in chemical communication and reproductive behavior.

Endocrinological correlates of male bimaturism in wild Bornean orangutans.

Among primates, orangutans are unique in having pronounced male bimaturism leading to two fully adult morphs that differ in both physical appearance and behavior. While unflanged males have a female-like appearance, flanged males have the full suite of secondary sexual characteristics, including cheek flanges and a large throat sac. So far, hormonal correlates of arrested development in unflanged males and the expression of secondary sexual characteristics in flanged males have only been studied in zoo-housed individuals. In this study, we investigated fecal androgen and glucocorticoid metabolites as hormonal correlates of male bimaturism in 17 wild adult Bornean orangutans (Pongo pygmaeus) in Central Kalimantan, Indonesia. We predicted and found higher androgen levels in flanged males compared to unflanged males, probably due to ongoing strong competition among flanged males who meet too infrequently to establish a clear linear dominance hierarchy. Furthermore, we found no difference in fecal glucocorticoid metabolite concentrations between flanged and unflanged males, indicating that social stress is unlikely to explain arrested development in unflanged wild orangutans. The only actively developing male in our study showed significantly higher androgen levels during the period of development than later as a fully flanged male. This supports earlier findings from zoo studies that elevated androgen levels are associated with the development of secondary sexual characteristics.

Fathead minnow (Pimephales promelas) reproduction is impaired when exposed to a naphthenic acid extract

Previous studies have demonstrated that oil sands process-affected water (OSPW) impairs the reproduction of fish and that naphthenic acids (NAs), a natural constituent of oil sands, are suspected of being responsible. This study evaluates the potential impact of NAs on the reproduction of adult fathead minnows (Pimephales promelas) under laboratory conditions. Fathead minnows exposed to a 10mg/l naphthenic acid extract (NAE) for 21 days spawned fewer eggs and males had reduced expression of secondary sexual characteristics. Male fathead minnows exposed to a 5mg/l NAE had lower plasma levels of 11-ketotestosterone whereas those exposed to a 10mg/l NAE had lower concentrations of both testosterone and 11-ketotestosterone. Since OSPW also contains high concentrations of salts, this study also investigated whether they modify the toxicity of NAEs. Spawning was significantly reduced in fathead minnows exposed to a 10mg/l NAE alone and in combination with NaHCO3 (700mg/l), typical of concentrations in OSPW. Interestingly, the addition of NaHCO3 reduced the inhibitory effects of the NAE on the numbers of reproductive tubercles and plasma testosterone levels. Further studies showed that NaHCO3 acted by reducing the uptake of the NAE to the fish. NaHCO3 but not NaCl or Na2SO4 reduced the acute toxic effects of the NAE on fathead minnow embryo and larvae mortality. Collectively, these studies show that the NAs in OSPW have the potential to negatively affect reproduction in fathead minnows and that HCO3− reduces the acute and chronic toxicity of NAs.

Effects of Triclosan and Triclocarban, Two Ubiquitous Environmental Contaminants, on Anatomy, Physiology, and Behavior of the Fathead Minnow (Pimephales promelas)

Triclosan (TCS) and triclocarban (TCC) are two common antimicrobial agents found in many personal care products and subsequently are detected ubiquitously in wastewater effluent and receiving waters. Both compounds are of recent regulatory interest due to their omnipresence in the environment, including in humans. Although TCS and TCC have been suggested to be endocrine active, little information exists about their effects on organismal end points in development (growth, escape performance), anatomy (morphological indices, histology), physiology (vitellogenin), and behavior of exposed aquatic organisms. In this study, newly hatched fathead minnows were exposed for 12 days, and mature male and female fathead minnows (Pimephales promelas) were exposed for 21 days to environmentally realistic concentrations (nanograms per liter) of these two compounds singularly and in mixtures. At the end of the exposure, larvae were assessed for growth and predator-avoidance performance, and a subset of mature fish was assessed for plasma vitellogenin induction, expression of secondary sexual characteristics, relative size of liver and gonads, and histopathological changes to both organs. The remaining exposed mature fish were placed in breeding pairs of one male and one female minnow from the same treatment to assess their ability to defend a nest site and reproduce. Exposure to either antimicrobial compound, alone or as a mixture, caused no changes to larval fish, gonad size, or vitellogenin concentrations in mature fathead minnows. In contrast, decreased aggression was seen in adult male fathead minnows exposed to TCC (1.6 μg/l) or a mixture (560 ng/l TCS + 179 ng/l TCC and 1.6 μg/l TCS + 450 ng/l TCC). Decreased aggression would likely decrease their ability to defend and hold a nest site needed for spawning and reproduction. Substantial variability was found in the severity of observed effects within treatments, suggesting that environmentally realistic concentrations of these compounds may only affect particularly sensitive individuals.

Embryonic survival and larval predator-avoidance ability in mutually ornamented whitefish

Mutual ornamentation (i.e. the expression of secondary sexual characters) in both sexes is a relatively common but rarely studied phenomenon in the animal kingdom. In the present study, we investigated whether mutual ornamentation is indicative of offspring embryonic survival and predator-avoidance ability in whitefish. We crossed ten randomly selected females and ten randomly selected males in all possible combinations resulting in 100 sib groups, and hypothesized that fitness (measured as offspring survival) of elaborately ornamented parents would be higher in both sexes of whitefish. Parental effects were found in both studied traits: effects of female and female–male interaction were significant for the embryonic mortality, whereas only paternal effect was found for the offspring predator-avoidance ability. As expected, increasing number of the female breeding tubercles was associated with low embryonic mortality, although male ornamentation was not indicative of offspring survival. The present study, together with earlier data, clearly demonstrate that offspring fitness is affected by parental identity, and suggest that mutual ornamentation in this species may indicate the genetic quality of individuals in both sexes. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103, 593–601.

Preliminary data on the influence of rearing temperature on the growth and reproductive status of fathead minnows Pimephales promelas

An investigation into the influence of temperature on the growth and reproductive status of the fathead minnow Pimephales promelas revealed that, while there was no clear effect of treatment on sex differentiation, ovarian tissue from female fish reared under the highest temperature regime contained large amounts of undefined tissue containing no germ cells. Furthermore, both male and female fish exhibited differences in length mass, condition and somatic indices, and in the expression of secondary sexual characteristics. The patterns observed are discussed in the context of climate change.

Realistic nitrate concentration alters the expression of sexual traits and olfactory male attractiveness in newts

Summary The occurrence of endocrine disruption is increasing and may now affect most, if not all, ecosystems. Owing to its impact on survival and reproduction, it is increasingly important to consider this factor in ecological studies. The study of secondary sexual traits is of particular interest because they are under strong hormonal control and play a crucial role in mating. A neglected sub‐lethal effect of endocrine disruption is the reduction of male attractiveness, and the distortion of the sexual selection process. Nitrate is one of the most widespread endocrine disruptors because of its extensive use in agriculture. Studies, especially in amphibians, have mostly focused on early developmental stages, probably because these were considered critical for population dynamics. However, negative effects on adult survival or reproductive success may also affect population demography. We surveyed nitrate concentration in a large sample of ponds. We then exposed male palmate newts, Triturus helveticus, to high (75 mg L−1) but realistic concentration of sodium nitrate to investigate the effect of nitrate on the expression of secondary sexual traits and male attractiveness. Exposure to nitrate for 3 weeks was found to limit the expression of sexual traits and to reduce body growth; exposure for 10 days reduced male attractiveness. Female preferred males unexposed to nitrate in olfactory tests but not in visual tests. The expression of secondary sexual characteristics and body size is reduced in males exposed to realistic nitrate concentration. However, a drop in male attractiveness may first be caused by disruption of the production of olfactory cues. Depending on the frequency of contaminated breeding sites, the disruption of male ability to express sexual signals might affect the sexual selection process in palmate newts and eventually reduce population reproductive output. We discuss the ecological and evolutionary implications of this result.

Territorial behaviour and immunity are mediated by juvenile hormone: the physiological basis of honest signalling?

Summary 1. The role of the juvenile hormone (JH) as a potential mediator in the trade-off between male‐ male competition and immune response has not been tested, but its study could reveal a potential mechanism that mediates resource allocation between these two traits. 2. Controlling for body size, we tested whether males of the territorial damselfly Calopteryx virgo administrated with methoprene acid, an analog of the JH (JHa), compared to control males, increased their aggression and occupation time on territories but decreased their phenoloxidase (PO) activity (a key enzyme used during immune response after a bacterial challenge). We found an increase in aggression in JHa treated males compared to control males, but the opposite was found for PO activity. 3. As fat load and muscle mass are also important traits during a contest, we tested whether JHa males compared to control males showed more fat and muscle content 2 h after JHa administration. Our results did not show a significant difference between both male groups, suggesting that JHa only increased aggression. 4. These results and a review of other published articles, which have documented an effect of JH on a variety of functions in insects, suggest that JH may be a target of sexual selection: this hormone not only promotes the expression of secondary sexual characters but also seems condition-dependent and so its titers may indicate male condition.

The expression of secondary sexual characteristics in recruit- and repeat-spawning farmed and wild Atlantic cod (Gadus morhua)

Abstract Skjæraasen, J. E., Meager, J. J., and Karlsen, Ø. 2008. The expression of secondary sexual characteristics in recruit- and repeat-spawning farmed and wild Atlantic cod (Gadus morhua). – ICES Journal of Marine Science, 65: 1710–1716. We examined the expression of the two known secondary sexual characteristics of Atlantic cod, the pelvic fin and the drumming muscle, in farmed and wild cod stemming from the same population. Farmed and wild males had longer pelvic fins and larger drumming muscles than females, but wild cod had longer fins than farmed cod. The size of the drumming muscle of males was similar among wild and farmed cod, but farmed females had smaller muscles than their wild counterparts. Repeat-spawning wild males tended to invest less in drumming-muscle mass and more in pelvic-fin growth than recruit-spawning fish, whereas the reverse was true for farmed males. Males use pelvic fins to embrace females during ventral mounts, a key mating behaviour, and display them to other males during agonistic interactions. The drumming muscle is used by males to produce sound during courtship and aggressive displays, whereas females only use sound outside the spawning season, for agonistic and defensive behaviours that are unlikely to be as important in the farming environment. The results are discussed in the context of the reproductive success of farmed escapees in the wild.

Melanin- and carotenoid-dependent signals of great tits (Parus major) relate differently to metal pollution

Due to their high phenotypic plasticity, the expression of secondary sexual characteristics is particularly sensitive to stress. Here, we investigated the expression of two conspicuous visual signals in great tits (Parus major) in a metal pollution gradient. In three study sites with marked differences in metal contamination (mainly lead, cadmium, copper and zinc), we compared melanin and carotenoid colouration of great tits. While carotenoid colouration (yellow breast) was negatively related to metal pollution, the size of a melanin trait (breast stripe) was larger in the most polluted sites. Environmental pollutants not only affect the expression of conspicuous signals but may even enhance, directly or indirectly, a signal of male quality such as breast stripe. Our results also support the multiple messages hypothesis predicting that different signals highlight different aspects of geno- and phenotypic condition of the bearer.

Digit ratios, secondary sexual characters and condition in barn swallows Hirundo rustica

The second and fourth digit length ratio (2D:4D) is sexually dimorphic in many vertebrates. This ratio has been suggested to provide an estimate of steroid levels encountered during prenatal development, which may have organizational consequences for physiology and behavior of adults. However, recent studies showed that the relation between digit ratio and steroids seems inconsistent and may vary among species and populations. We tested the hypothesis that digit ratios would be correlated with the expression of secondary sexual characters, using the barn swallow (Hirundo rustica) as a model system. This was done by testing whether variation in 2D:4D ratio was correlated with tail length and features of song, which are important secondary sexual characters positively correlated with circulating steroid concentration in adult birds. Furthermore, we examined the prediction that male and female digit ratios would correlate with body mass in an antagonistic way. There was no significant sexual dimorphism in digit ratio, which may be due to low levels of sexual selection in this population. Adult right 2D:4D ratio was negatively linked to tail length but not to male song output. Moreover, right 2D:4D ratio was negatively correlated with body mass in male and positively in females. These results are consistent with high digit ratios reflecting low levels of testosterone in this bird species. Key words: bird song, digit ratio, Hirundo rustica, morphology, secondary sexual characters. [Behav Ecol]

Alternative male reproductive tactics and the immunocompetence handicap in the Azorean rock-pool blenny, Parablennius parvicornis

In the Azorean rock-pool blenny (Parablennius parvicornis) reproductively active males display alternative morphotypes, which differ in the expression of secondary sexual characters (SSC). Males expressing SSC, the M+ morphotype, have high androgen levels and compete for crevices that will be visited by females to spawn. M+ males holding nests court females and care for the eggs. Males with low expression of SSC, the M- morphotype, have low levels of androgens and reproduce by stealing fertilizations from the M+ males. Based on the hypothesis that androgens are immunosuppressive, we expected these morphotypes to differ in immunocompetence. To test this hypothesis, we conducted a field study in which we collected repeated blood samples to monitor leukocyte populations (blood smears), and to measure the primary antibody response of males that were experimentally challenged with a foreign non-pathogenic antigen (sheep red blood cells). Circulating levels of 11-ketotestosterone and testosterone were higher in M+ males than in M- males. Neither granulocyte nor thrombocyte counts did covariate with androgens or male tactic. In contrast, lymphocyte counts and humoral antibody response were negatively correlated with body size, and as expected, both were lower in M+ than in M- males. Interestingly, in M+ males androgen levels decreased after immunization, and this was less in nest-holder males than in M+ males that were floating around in the pools. Within each morphotype we found no relationship between androgens and immunocompetence. The latter result is not supportive for androgen regulated immunosuppression in M+ males. A possible alternative is enhancement of immunity in M- males. These males had relatively high levels of injuries in comparison with M+ males. High immunity might be a consequence of high infection rate because of such injuries.

Regulation of immunocompetence by different androgen metabolites in a blenny with alternative reproductive tactics

In Parablennius parvicornis, small reproductive males with relatively low expression of secondary sexual characters (M- morphotype) parasite on the parental investment of the larger nest-holder males which have fully developed secondary sexual characters (M+ morphotype). In comparison with M+ males, M- males have relatively low levels of androgens while having high blood cell percentages of lymphocytes and antigen responsiveness. Here we test the hypothesis that androgens are a causal factor for these differences in immunocompetence between morphotypes. After drawing an initial blood sample, males received a silastic implant containing either oil only (C), or oil with testosterone (T) or 11-ketotestosterone (KT). Males were re-caught 2 weeks later for drawing of the final blood sample. KT but not T induced the development of secondary sexual characters in M- males. M- males treated with KT showed lower swimming activity than the males treated with T or C implants, suggesting that KT also mediates behavioral changes in M- males. As expected, blood cell percentages of lymphocytes, but not of granulocytes, were higher in M- males than in M+ males. Overall, lymphocyte percentages increased in the C group which might have been a response to the surgery/treatment. In concordance with the hypothesis, lymphocyte percentages were suppressed in males treated with T in comparison with controls. However, no significant change was found in KT-treated males. This suggests that androgens modulate central, morphological and immunological traits by partly independent androgen mechanisms in P. parvicornis.

BATEMAN'S PRINCIPLE AND IMMUNITY: PHENOTYPICALLY PLASTIC REPRODUCTIVE STRATEGIES PREDICT CHANGES IN IMMUNOLOGICAL SEX DIFFERENCES

The sexes often differ in the reproductive trait limiting their fitness, an observation known as Bateman's principle. In many species, females are limited by their ability to produce eggs while males are limited by their ability to compete for and successfully fertilize those eggs. As well as promoting the evolution of sex-specific reproductive strategies, this difference may promote sex differences in other life-history traits due to their correlated effects. Sex differences in disease susceptibility and immune function are common. Two hypotheses based on Bateman's principle have been proposed to explain this pattern: that selection to prolong the period of egg production favors improved immune function in females, or that the expression of secondary sexual characteristics reduces immune function in males. Both hypotheses predict a relatively fixed pattern of reduced male immune function, at least in sexually mature individuals. An alternative hypothesis is that Bateman's principle does not dictate fixed patterns of reproductive investment, but favors phenotypically plastic reproductive strategies with males and females adaptively responding to variation in fitness-limiting resource availability. Under this hypothesis, neither sex is expected to possess intrinsically superior immune function, and immunological sex differences may vary in different environments. We demonstrate that sex-specific responses to experimental manipulation of fitness-limiting resources affects both the magnitude and direction of sex differences in immune function in Drosophila melanogaster. In the absence of sexual interactions and given abundant food, the immune function of adults was maximized in both sexes and there was no sex difference. Manipulation of food availability and sexual activity resulted in female-biased immune suppression when food was limited, and male-biased immune suppression when sexual activity was high and food was abundant. The immunological cost to males of increased sexual activity was found to be due in part to reduced time spent feeding. We suggest that for species similarly limited in their reproduction, phenotypic plasticity will be an important determinant of sex differences in immune function and other life-history traits.

CLIMATIC AND TEMPORAL EFFECTS ON THE EXPRESSION OF SECONDARY SEXUAL CHARACTERS: GENETIC AND ENVIRONMENTAL COMPONENTS

Despite great interest in sexual selection, relatively little is known in detail about the genetic and environmental determinants of secondary sexual characters in natural populations. Such information is important for determining the way in which populations may respond to sexual selection. We report analyses of genetic and large-scale environmental components of phenotypic variation of two secondary sexual plumage characters (forehead and wing patch size) in the collared flycatcher Ficedula albicollis over a 22-year period. We found significant heritability for both characters but little genetic covariance between the two. We found a positive association between forehead patch size and a large-scale climatic index, the North Atlantic Oscillation (NAO) index, but not for wing patch. This pattern was observed in both cross-sectional and longitudinal data suggesting that the population response to NAO index can be explained as the result of phenotypic plasticity. Heritability of forehead patch size for old males, calculated under favorable conditions (NAO index > or = median), was greater than that under unfavorable conditions (NAO index < median). These changes occurred because there were opposing changes in additive genetic variance (VA) and residual variance (VR) under favorable and unfavorable conditions, with VA increasing and VR decreasing in good environments. However, no such effect was detected for young birds, or for wing patch size in either age class. In addition to these environmental effects on both phenotypic and genetic variances, we found evidence for a significant decrease of forehead patch size over time in older birds. This change appears to be caused by a change in the sign of viability selection on forehead patch size, which is associated with a decline in the breeding value of multiple breeders. Our data thus reveal complex patterns of environmental influence on the expression of secondary sexual characters, which may have important implications for understanding selection and evolution of these characters.