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1.
The estimation of individual fluctuating asymmetry (FA) is subject to large sampling variabilities. Heritability estimates, as well as correlations between developmental stability and any other individual character and/or between-trait correlations, are consequently biased downward if FA is used as an estimate of an individual''s ability to buffer its development against developmental noise. The estimation of the hypothetical repeatability, defined as the ratio of the between-individual component of variation in the unsigned FA divided by the total variance, allows correction for these biases such that patterns observed for FA can be translated to make inferences about the presumed underlying developmental stability. In this paper I show that previous estimates of this repeatability are incorrect. I provide a new method and show by means of simulations that the hypothetical repeatability is in most cases even lower than previously thought. This has important consequences for the analysis of FA with respect to statistical power and the interpretation of patterns in FA.  相似文献   

2.
Humans find symmetrical faces more attractive than are asymmetricalfaces. Evolutionary psychologists claim that our preferencefor symmetry can be explained in the context of mate choicebecause symmetry is an honest indicator of the genetic qualityof potential mates. These arguments assume that asymmetry inhuman faces is fluctuating asymmetry (FA), because this formof asymmetry can be revealing of developmental instability.However, no study has yet examined the characteristics of facialasymmetry. Here we provide the first detailed study of the patternsof asymmetry in human faces. We measured asymmetry in 35 facialtraits. Although some traits had distributions characteristicof FA, many had distributions that characterize directionalasymmetry (DA); on average, both men and women had right hemi-facedominance. For DA traits we used deviations from the mean asymmetryas a measure of developmental instability. Our measures of asymmetryaccounted for a moderate proportion of the variance in perceivedsymmetry. Importantly, only FAs and random deviations from DAcontributed to people's perception of symmetry. DA was not importantin symmetry judgments. Faces rated as symmetrical were alsorated as attractive. Random deviations from DA were weakly relatedto women's attractiveness judgments of men's faces. DAs didnot influence attractiveness judgments. Our data suggest thatpeople focus on aspects of facial asymmetry that may be revealingof developmental instability. Further studies that isolate FAfrom other forms of asymmetry are required to accurately assessthe influence of developmental instability on the quality ofindividuals and its potential role in mate preferences.  相似文献   

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Body size and morphology are key fitness-determining traits that can vary genotypically. They are likely to be important in social insect queens, which mate in swarms and found colonies independently, but genetic influences on queen morphology have been little investigated. Here, we show that the body size and morphology of queens are influenced by their genotype in the leaf-cutting ant Acromyrmex echinatior, a species in which certain lineages (patrilines) bias their development towards reproductive queens rather than sterile workers. We found no relationship between the queen-worker skew of patrilines and the size or morphology of queens, but there was a significant relationship with fluctuating asymmetry, which was greater in more queen-biased patrilines. Our results suggest that queen-biased patrilines do not incur a fitness cost in terms of body size, but may face more subtle costs in developmental stability. Such costs may constrain the evolution of royal cheating in social insects.  相似文献   

5.
Generally, immune system architecture varies with different environments, which presumably reflect different pathogen pressures. Specifically, populations from relatively disease-free, oceanic islands are expected to exhibit reorganized immune systems, which might be characterized by attenuated responses, given the costs of immune function. Some insular animals exhibit an 'island syndrome,' including increased susceptibility to disease, and some insular populations have declined when they failed to resist infection by introduced pathogens. I measured eight indices of immune function (haemolysis, haemagglutination, concentration of haptoglobin and concentration of five leukocyte types) in 15 phylogenetically matched pairs of bird populations from North America and from the islands of Hawaii, Bermuda and the Galápagos. Immune responses were not attenuated in insular birds, and several indices, including the concentration of plasma haptoglobin, were elevated. Thus, I find no support for the specific hypothesis that depauperate parasite communities and the costs of immune defences select for reduced immune function. Instead, I suggest that life on islands leads to an apparent reorganization of immune function, which is defined by increases in defences that are innate and inducible. These increases might signal that systems of acquired humoral immunity and immunological memory are less important or dysfunctional in island populations.  相似文献   

6.
1.?The growth period is an important determinant of fitness later in life through its effects on first-year survival and future reproduction. Choices by adult females about where to rear their offspring strongly affect growth rates and offspring fitness in geese. 2.?Individual female black brent (Branta bernicla nigricans) tend to raise their broods in the same areas each year, and these areas are consistently ranked with respect to growth rates of goslings. Therefore, some females consistently rear their broods on areas resulting in lower post-fledging fitness. 3.?We explore the potential that growth rates of offspring (and associated fitness consequences) are traded off against other vital rates influencing fitness of either adult females or goslings. Growth of goslings primarily influences fitness after fledging, so one hypothesis is that survival before fledging, which is influenced by predation, is traded off against growth rates and post-fledging survival. 4.?We estimated pre-fledging and post-fledging survival for goslings reared on areas used by broods from the Tutakoke River black brent colony. We examined recaptures, recoveries by hunters and resightings of brent marked as goslings with webtags and standard leg rings. These data were analyzed using capture-mark-recapture models in program mark to derive separate estimates of pre- and post-fledging survival for 18 cohorts (1987-2004) of black brent goslings across seven brood rearing areas (BRAs). 5.?Estimates of pre-fledging survival probability varied from 0·00?±?0·00 (mean?±?95% confidence interval) to 0·92?±?0·1; and estimates of post-fledging survival probability varied from 0·00?±?0·00 to 1·00?±?0·08. Substantial variation existed both among BRAs and years but post-fledging survival declined substantially during the study. 6.?Pre- and post-fledging survival were positively correlated, exhibiting a quadratic relationship (?(post-fledging survival) =?1·00 (±0·47)x-0·83 (±0·480)x(2) , where x?=?pre-fledging survival). Therefore, we did not find a trade-off between pre- and post-fledging survival in black brent goslings across BRAs, suggesting that factors other than foraging conditions and predation on goslings must influence selection of BRAs.  相似文献   

7.
Most of the studies on sunlight-induced pigmentation of skin are mainly focused on ultraviolet (UV) radiation-induced pigmentation and ways to prevent it. Recent studies have shown that the visible component of sunlight can also cause significant skin pigmentation. In the current study, the extent of pigmentation induced by UV and visible regions of sunlight in subjects with Fitzpatrick skin type IV-V was measured and compared with pigmentation induced by total sunlight. The immediate pigment darkening (IPD) induced by the visible fraction of sunlight is not significantly different from that induced by the UV fraction. However, the persistent pigment darkening (PPD) induced by visible fraction of sunlight in significantly lower than that induced by the UV fraction. The dose responses of IPD induced by UV, visible light and total sunlight suggest that both UV and visible light interact with the same precursor although UV is 25 times more efficient in inducing pigmentation per J cm(-2) of irradiation compared to visible radiation. The measured diffused reflection spectra and decay kinetics of UV and visible radiation-induced pigmentation are very similar, indicating that the nature of the transient and persistent species involved in both the processes are also likely to be same.  相似文献   

8.
Argyrophilic nucleolar organizing region associated proteins (AgNORs) play roles in cell proliferation and a variety of diseases. We attempted to determine whether decreased NOR protein synthesis causes human hair loss. We studied 21 healthy males who suffered hair loss on the frontal/vertex portion of the head. Hair root cells from normal and hair loss sites were stained for AgNOR. One hundred nuclei per site were evaluated and the AgNOR number and NORa/TNa proportions of individual cells were determined using a computer program. The cells from normal sites had significantly higher AgNOR counts than those from hair loss sites. Also, the cells from the normal sites had significantly higher NORa/TNa than cells from the hair loss sites. In the normal sites, the cells demonstrated more NOR protein synthesis than cells in hair loss sites. Therefore, decreased NOR protein synthesis appears to be related to hair loss in humans.  相似文献   

9.
Stimulation of human neutrophils with the chemoattractant N-formyl peptide caused rapid polymerization of F-actin as detected by right angle light scatter and 7-nitrobenz-2-oxa-1,3-diazol (NBD)-phallacidin staining of F-actin. After labeling neutrophils with 32P, exposure to N-formyl peptide induced a fast decrease of phosphatidylinositol 4-bisphosphate (PIP)2, a slow increase of phosphatidic acid, and a rapid rise of phosphatidylinositol 4-trisphosphate (PIP3). Formation of PIP3 as well as actin polymerization was near maximal at 10 s after stimulation. Half-maximal response and PIP3 formation at early time points resulted from stimulation of neutrophils with 0.01 nM N-formyl peptide or occupation of about 200 receptors. Sustained elevation of PIP3, prolonged right angle light scatter response, and F-actin formation required higher concentrations of N-formyl peptide, occupation of thousands of receptors, and high binding rates. When ligand binding was interrupted with an antagonist, F-actin rapidly depolymerized, transient light scatter response recovered immediately, and elevated [32P]PIP3 levels decayed toward initial values. However, recovery of [32P]PIP2 was not influenced by the antagonist. Based on the parallel time courses and dose response of [32P] PIP3, the right angle light scatter response, and F-actin polymerization, PIP3 is more likely than PIP2 to be involved in modulation of actin polymerization and depolymerization in vivo.  相似文献   

10.
Fluctuating asymmetry (FA), the deviation from the normal symmetrical condition of a morphological trait having specific morphological symmetry, increases in response to environmental and genetic stress, is related to phenotypic plasticity and is considered a tool for monitoring a species conservation status. However, FA–stress relations are dependent on measured traits or species‐specific characteristics such as mating system and habitat. This study investigates the relationships between FA, genetic diversity, population size, density and individual fitness traits (plant height, fruit and seed set), in the endemic Aquilegia thalictrifolia, a mixed breeder that is declining, but maintaining high levels of heterozygosity. Leaf and flower FA and other traits were investigated in 10 populations of A. thalictrifolia, the whole species range. As a result, we found similar patterns of FA in leaves and flowers between populations, indicating a homogenous level of stress between populations that differed for other traits. FA and the other traits were not related, including heterozygosity. Heterozygosity was not related to individual fitness traits with the exception of plant height. In accordance with other studies, we found that the role of FA as a tool for assessing the conservation status of a species or population should be reconsidered. However, we conclude that a low level of FA should not automatically be considered an indicator of good conservation status or low level of stress, because in species that evolved in highly stable environments it may indicate a scarce ability to plastically respond to environmental changes, as a consequence of environmental and genetic canalization. Further investigation of this point is needed.  相似文献   

11.
Maria Reuter 《Hydrobiologia》1991,227(1):221-227
The ultrastructure of the CNS (central nervous system) in three species of the Proseriata — Archiloa unipunctata (O. Fabricius), Bothriomolus balticus (Meixner), and Promonotus schultzei (Meixner) — was studied and compared to that of the lower flatworms Stenostomum leucops (Catenulida) and Microstomum lineare (Macrostomida) in material available from our previous studies. Conventional electron microscopical fixation was used for A. unipunctata and B. balticus; the tannic-acid-incubation method (TARI), a method that reveals especially nonsynaptic exocytotic release of neuronal substances, was applied in study of P. schultzei.In general, the ultrastructural features of neurons and nerve fibers were similar in proseriates and lower flatworms. A striking feature common to both groups was the secretory appearance of all neurons. A significant difference between them is the occurrence, in the proseriates, of wrapping of neurons by glial cells. Heterogeneity in the population of neuronal vesicles and in structure of synapses in the proseriates are probably advanced characters; by contrast, S. leucops has relatively homogeneous vesicles and simple synapses. A gradual advancement from the state in the catenulids through that in the macrostomids to the proseriates seems to be reflected in the differentiation of synapses and the variability of neuronal vesicles. This probably reflects differences in functional demands but also evolutionary advancement.  相似文献   

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Previous studies have shown an association between low concentration of serum cholesterol, as well as high concentration of serum cortisol, in suicide behavior. The aim of this study was to evaluate whether men after a violent suicide attempts have different serum cholesterol and cortisol concentrations than those who attempted suicide by non-violent methods. Venous blood samples were collected within 24 hours of admission, to study concentrations of serum cholesterol and cortisol. The sample consisted of 31 male subjects suffering from schizophrenia, admitted in a general hospital after suicide attempt, and was compared with 15 schizophrenic nonsuicidal male controls. Patients with a violent suicidal attempt were found to have significantly lower cholesterol levels and significantly higher cortisol level than patients with non-violent attempts and the control subjects. Our findings suggest that suicide attempts should not be considered a homogenous group. The hypothesis of an association of violent suicidal attempts and peripheral biological markers (cholesterol and cortisol) was supported by our findings.  相似文献   

14.
Twins provide a unique capacity to explore relative genetic and environmental contributions to brain development, but results are applicable to non‐twin populations only to the extent that twin and singleton brains are alike. A reason to suspect differences is that as a group twins are more likely than singletons to experience adverse prenatal and perinatal events that may affect brain development. We sought to assess whether this increased risk leads to differences in child or adolescent brain anatomy in twins who do not experience behavioral or neurological sequelae during the perinatal period. Brain MRI scans of 185 healthy pediatric twins (mean age = 11.0, SD = 3.6) were compared to scans of 167 age‐ and sex‐matched unrelated singletons on brain structures measured, which included gray and white matter lobar volumes, ventricular volume, and area of the corpus callosum. There were no significant differences between groups for any structure, despite sufficient power for low type II (i.e. false negative) error. The implications of these results are twofold: (1) within this age range and for these measures, it is appropriate to include healthy twins in studies of typical brain development, and (2) findings regarding heritability of brain structures obtained from twin studies can be generalized to non‐twin populations.  相似文献   

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Rate of grain filling in terms of dry mass accumulated per panicle per day was measured in field-grown rice in the dry season in the Philippines and compared to rates of light-saturated photosynthesis per unit leaf area (P(max)) measured at 350 micro l l(-1) CO(2) for 21 d after flowering. Five new plant type (tropical japonica) varieties (NPT) and one indica variety (IR72) were used and these gave some variation in rates and patterns of grain filling. A rapid grain-filling phase (RGFP) occurred approximately 10 d after flowering in most varieties. There was no consistent relationship in any variety between the rate of grain-filling and P(max) and chlorophyll content, both of which remained mostly unchanged throughout grain filling. Significant declines in the amount of total leaf protein and ribulose bisphosphate carboxylase-oxygenase (Rubisco) occurred, but these did not occur at the same time as the RGFP in all varieties. A decrease in the ratio of chlorophyll a/b preceded these changes and a transient rise in chlorophyll content was also observed in four varieties at this time. There was no significant change in leaf non-structural carbohydrate content during or following the RGFP. It is concluded that the decline in Rubisco and protein content in NPT was not reflected in photosynthetic activity. Hence in these field experiments Rubisco accumulated to a level in excess of photosynthetic requirements, serving as a store of nitrogen for grain filling.  相似文献   

17.
In recent years, there has been an increase in research to understand how global changes’ impacts on soil biota translate into altered ecosystem functioning. However, results vary between global change effects, soil taxa, and ecosystem processes studied, and a synthesis of relationships is lacking. Therefore, here we initiate such a synthesis to assess whether the effect size of global change drivers (elevated CO2, N deposition, and warming) on soil microbial abundance is related with the effect size of these drivers on ecosystem functioning (plant biomass, soil C cycle, and soil N cycle) using meta‐analysis and structural equation modeling. For N deposition and warming, the global change effect size on soil microbes was positively associated with the global change effect size on ecosystem functioning, and these relationships were consistent across taxa and ecosystem processes. However, for elevated CO2, such links were more taxon and ecosystem process specific. For example, fungal abundance responses to elevated CO2 were positively correlated with those of plant biomass but negatively with those of the N cycle. Our results go beyond previous assessments of the sensitivity of soil microbes and ecosystem processes to global change, and demonstrate the existence of general links between the responses of soil microbial abundance and ecosystem functioning. Further we identify critical areas for future research, specifically altered precipitation, soil fauna, soil community composition, and litter decomposition, that are need to better quantify the ecosystem consequences of global change impacts on soil biodiversity.  相似文献   

18.
Extinction and artificial reduction in the size of geographical ranges of many species have occurred extensively across the globe because of human activities. In particular, Australian mammals have suffered heavily in the last two hundred years, with the highest number of reported cases of mammal extinctions anywhere. In the present study, we investigated the extent to which human impact has affected contemporary macroecological patterns in Australian terrestrial mammals. After examining patterns relating to body size and range size among the contemporary mammal fauna, we removed the effects of the last two hundred years of human impact by exploring patterns in the pre‐European assemblage. This permitted us to determine whether contemporary macroecological patterns are distortions of pre‐European patterns. In contrast to the expected pattern of a significant positive relationship between body size and range size, our results showed no significant association for the complete fauna in both cross‐species and phylogenetic analyses, even when data were corrected for species extinctions and range reductions. Analyses within families and among species with the same dietary strategy revealed three significant positive relationships (Macropodidae, Peramelidae, and herbivores) and one significant negative relationship (insectivores) within the contemporary assemblage that disappeared when the pre‐European assemblage was analysed. A positive relationship also emerged in the pre‐European assemblage for the Vombatidae that was not apparent in the contemporary fauna. Thus, correcting for human impact revealed important distortions among contemporary macroecological relationships that have been brought about by human‐induced range reduction and extinction. These findings not only provide further evidence that the Australian continent presents a unique and valuable opportunity with which to test the generality of macroecological patterns, but they also have important ramifications for the analysis and interpretation of contemporary macroecological datasets.  相似文献   

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20.
"New pressor protein" (NPP) derived from normal human plasma is an extra renal enzyme that shares strong sequence homology with human coagulation beta-FXIIa. Under our bioassay conditions, human NPP (10-20 microl plasma equivalent/ approximately 300 g rat iv) can raise the systolic blood pressure (SBP) by 40-50 mmHg, the diastolic blood pressure (DBP) by 15-20 mmHg, and the heart rate (HR) by 70-90 beats/min. Plasma epinephrine (of adrenal medullary origin) and norepinephrine rise by about 50- and 10-fold, respectively. Because beta-FXIIa is not normally associated with pressor properties, we endeavored to substantiate that the hypertensive effects of impure NPP preparations used in our experiments are attributable to their content of beta-FXIIa. We carried out comparisons with highly purified (>90%) commercial human beta-FXIIa and found that by gel filtration (Sephadex G-100 and G-75), NPP bioactivity appeared in the approximately 30-kDa elution zone, consistent with the molecular mass of beta-FXIIa. Retention time using fast-protein liquid chromatography anion exchange chromatography was identical. Molecular mass and comigration were confirmed by SDS-PAGE gel electrophoresis, and the recovered approximately 30-kDa protein bands yielded beta-FXIIa fragments identified by mass spectrometry. Matched doses of the NPP preparations produced dose-response curves very similar to those elicited by beta-FXIIa with respect to increments of SBP, DBP, and HR, whereas plasma catecholamine increments were generally comparable. We propose that beta-FXIIa is substantially, if not exclusively, responsible for the observed effects of our NPP preparations and that this points to a novel axis connecting the FXII coagulation cascade and the sympathoadrenal gland to other cardiovascular regulatory mechanisms.  相似文献   

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