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1.
Stress may have consequences for the evolution of condition-dependentsexual traits. For example, stress may be related to sexualtraits through immune function, and sexual traits can reflecthow individuals bear the costs of stress-mediated immunosuppression.However, male traits may be directly associated with stress,and such traits would then indicate stress tolerance. Here,we present initial results for the relationship between physiologicalstress estimated by the levels of heat shock proteins (HSP60and HSP70) and heterophil/lymphocyte ratio and the elaborationof sexual traits, such as forehead and wing patch size and songfeatures in the collared flycatcher Ficedula albicollis. Malesproducing longer and more versatile songs had significantlyhigher levels of HSP70, but other traits were unrelated to stress.In general, effect sizes for the relationship between stressand sexual traits had broad confidence intervals and variedbetween being small and medium effects. Immunoglobulin levels,leukocyte abundance, haemoparasite prevalence, male age, anddate and time effects did not affect the relationship betweenstress and sexual traits. These preliminary results, servinga basis for further experimental studies indicate that the relationshipbetween sexual traits and stress does not seem to be strong,but stress may partially constrain the expression of some sexualtraits.  相似文献   
2.
Male birds use song to attract mates and deter other males,but in doing so, they also attract the attention of predatorsand parasites. Such viability costs are inherent in reliablesignals, potentially causing females to prefer mates that displayfrom the most exposed sites. However, viability costs of sexualsignals may be ameliorated by affecting the choice of microhabitat,which in turn may affect the design of song features that aremost efficiently transmitted in this microhabitat. We estimatedthe exposure of song posts (microsites used by males when singing)used by passerine birds in relation to prey selection by thesparrowhawk Accipiter nisus, by calculating the proportion ofmales that sang from song posts that were at the maximum levelof the vegetation, in an attempt to quantify the costs of sexualselection. We quantified prey susceptibility to predation asthe difference between the log-transformed observed number ofprey minus the log-transformed expected number of prey in theenvironment. This prey susceptibility index increased with increasingsong post exposure similarly in sexually dichromatic and monochromaticspecies, although the prey susceptibility index was relatedto sexual dichromatism. Song post exposure was dependent onhabitat, but comparative models controlling for the potentiallyconfounding effects of habitat, sexual dichromatism, hole nesting,coloniality, body mass, cognitive capacities, and flying abilitiesindicated that the relationship between the prey susceptibilityindex and song post exposure is strong. Path analyses of therelationship between song post exposure, sexual dichromatism,and prey susceptibility index revealed that selection actingon sexual dichromatism and song post exposure has secondaryimpact on prey susceptibility index. The opposite causal mechanismsby which predation affects sexual traits are less likely. Thesemodels suggest that female preference for high song posts ordichromatic plumage increases predation risk on an evolutionarytime scale.  相似文献   
3.
Identifying evolutionary and developmental mechanisms underlying consistent between‐individual differences in behaviour is the main goal in ‘animal personality studies’. Here, we explored whether activity and risk‐taking varied consistently between individuals and correlated to various – potentially fitness linked – male traits in Carpetan rock lizards (Iberolacerta cyreni). Lizards showed significant consistency within both behaviours, implying the presence of activity and risk‐taking personalities. However, there were no correlation between activity and risk‐taking, neither on the between‐ nor on the within‐individual levels, implying the absence of a behavioural syndrome. We found a strong link between the intensity of blood parasite (Haemogregarinidae) infection and risk‐taking: lizards with higher infection intensity took more risk. While we cannot distinguish cause from causative in the parasite intensity – risk‐taking correlation – our results are in line with the asset protection hypothesis predicting that individuals with lower future reproductive value should focus on the current reproductive event and take higher risk.  相似文献   
4.
Secondary sexual characters may have evolved in part to signalresistance to parasites. Avian song has been hypothesized tobe involved in this process, but the role of parasites in modulatingacoustic communication systems in birds remains largely unknown,owing to lack of experiments. We studied the relationship betweenparasitism, testosterone, song performance, and mating successin male collared flycatchers (Ficedula albicollis) by experimentallychallenging their immune system with a novel antigen. We predictedthat a challenge of the immune system would reduce song performance,and that this reduction would be conditional on the size ofa visual sexual signal, the forehead patch that was previouslyfound to reflect resistance. An antagonistic linkage betweentestosterone and immune function would predict that a challengeof the immune system should suppress testosterone level. Animmunological treatment by sheep red blood cells (SRBCs) triggereda decrease in body mass, testosterone level, and song rate,but other song traits were not significantly affected by theantigen challenge. Initial testosterone level was associatedwith forehead patch size and all song traits except song rate.SRBC injection caused stronger reduction in song rate amongmales with smaller forehead patches, and the change in songrate was also predictable by song features such as strophe complexityand length. We show that song rate and other song characteristicsmay be important cues in male-male competition and female choice.These results suggest that parasite-mediated sexual selectionhas contributed in shaping a complex acoustic communicationsystem in the collared flycatcher, and that testosterone mayplay an important role in this process. Parasitism may drivea multiple signaling mechanism involving acoustic and visualtraits with different signal function.  相似文献   
5.
Theory predicts that parents adjust the sex ratio of their brood to the sexually selected traits of their mate because the reproductive success of sons may be more dependent on inherited paternal attractiveness than that of daughters. Empirical studies vary in terms of whether they support the theory, and this variation has often been regarded as evidence against sex ratio adjustment or has been ascribed to methodological differences. Applying phylogenetic meta‐analyses, we aimed to find biological explanations for the variation observed in songbirds. In particular, we tested the role extra‐pair paternity, because infidelity occurs in the majority of these species and may reduce the adaptive value of adjusting brood sex ratio to the phenotype of the social mate. However, we found that the variation in effect sizes was unrelated to the proportion of extra‐pair paternity. Thus future studies should consider that mate quality dependent sex ratio adjustment may be driven by direct (material) rather than indirect (genetic) benefits. We also tested if the effect sizes are influenced by whether the focal male trait is indeed under sexual selection as it is assumed by the sex allocation theory. We found that for male traits with proven role in sexual selection, effect sizes significantly differed from the null expectation of random production of sons and daughters. For male traits with only presumed sexual role in sexual selection, the deviation from the null expectation was less convincing, and the effect sizes were significantly smaller. This result indicates that studies that neglect the assumptions of the hypotheses concerned, may lead to the underestimation of the mean effect size and, eventually, false conclusions.  相似文献   
6.
Several hypotheses predict that the major histocompatibility complex (MHC) drives mating preference in females. Olfactory, colour or morphological traits are often found as reliable signals of the MHC profile, but the role of avian song mediating MHC‐based female choice remains largely unexplored. We investigated the relationship between several MHC and acoustic features in the collared flycatcher (Ficedula albicollis), a European passerine with complex songs. We screened a fragment of the class IIB second exon of the MHC molecule, of which individuals harbour 4–15 alleles, while considerable sequence diversity is maintained at the population level. To make statistical inferences from a large number of comparisons, we adopted both null‐hypothesis testing and effect size framework in combination with randomization procedures. After controlling for potential confounding factors, neither MHC allelic diversity nor the presence of particular alleles was associated remarkably with the investigated qualitative and quantitative song traits. Furthermore, genetic similarity among males based on MHC sequences was not reflected by the similarity in their song based on syllable content. Overall, these results suggest that the relationship between features of song and the allelic composition and diversity of MHC is not strong in the studied species. However, a biologically motivated analysis revealed that individuals that harbour an MHC allele that impairs survival perform songs with broader frequency range. This finding suggests that certain aspects of the song may bear reliable information concerning the MHC profile of the individuals, which can be used by females to optimize mate choice.  相似文献   
7.
In a current procedure for periodontal tissue regeneration, enamel matrix derivative (EMD), which is the active component, is mixed with a propylene glycol alginate (PGA) gel carrier and applied directly to the periodontal defect. Exposure of EMD to physiological conditions then causes it to precipitate. However, environmental changes during manufacture and storage may result in modifications to the conformation of the EMD proteins, and eventually premature phase separation of the gel and a loss in therapeutic effectiveness. The present work relates to efforts to improve the stability of EMD-based formulations such as Emdogain through the incorporation of arginine, a well-known protein stabilizer, but one that to our knowledge has not so far been considered for this purpose. Representative EMD-buffer solutions with and without arginine were analyzed by 3D-dynamic light scattering, UV-Vis spectroscopy, transmission electron microscopy and Fourier transform infrared spectroscopy at different acidic pH and temperatures, T, in order to simulate the effect of pH variations and thermal stress during manufacture and storage. The results provided evidence that arginine may indeed stabilize EMD against irreversible aggregation with respect to variations in pH and T under these conditions. Moreover, stopped-flow transmittance measurements indicated arginine addition not to suppress precipitation of EMD from either the buffers or the PGA gel carrier when the pH was raised to 7, a fundamental requirement for dental applications.  相似文献   
8.
Intestinal mucosal damage was produced in rats by the s.c. administration of indomethacin (10 mg/kg). The number and severity of the small intestinal mucosal lesions was recorded. Different doses of prostacyclin (PGI2), 7-oxo-PGI2 and 17-aza-PGF2 alpha (0.25-0.5-1.00 mg/kg) were given i.p. at the time of administration of indomethacin. The effects of these compounds were studied on the number and severity of the small intestinal mucosal lesions. It was shown that (1) all tested compounds inhibited the number and severity of the intestinal mucosal lesions, however, to different extent; (2) the inhibition of the development of small intestinal mucosal damage displayed a dose-response relationship; (3) 17-aza-PGF2 alpha was found to have the most potent effect on the development of the intestinal lesions as well as on the development of gastric mucosal damage produced by ethanol.  相似文献   
9.
Avian brood parasites have evolved striking begging abilitythat often allows them to prevail over the host progeny in competitionfor parental resources. Host young are therefore selected bybrood parasites to evolve behavioral strategies that reducethe cost of parasitism. We tested the prediction that the intensityof nestling begging displays functioning to attract parentalcare increases across species with the frequency of parasitismby the brown-headed cowbird (Molothrus ater). This was expectedbecause host young should try to prevail over highly competitiveparasitic broodmates in scramble interactions, act more selfishlywhen frequency of parasitism is high because brood parasitesoften affect more severely host condition than conspecific broodmates,and discount the kin selection costs of subtracting resourcesto unrelated parasites. Across 31 North American host species,begging loudness positively covaried with parasitism rate inPasserines, and such effect was stronger in species with smallcompared with large clutches. Begging loudness increased withbrood parasitism and nest predation among the most suitablehost species. These results held after controlling for concomitantecological factors and for common ancestry effects. Our resultssupport the hypothesis that avian brood parasitism has playeda role in the evolution of begging behavior of host young.  相似文献   
10.
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