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Anders Pape Moller - One of the best experts on this subject based on the ideXlab platform.
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A meta-analysis of Fluctuating Asymmetry in relation to heterozygosity
Heredity, 1999Co-Authors: Leif Asbjørn Vøllestad, Kjetil Hindar, Anders Pape MollerAbstract:Fluctuating Asymmetry, the random departure from perfect bilateral symmetry, is a common measure of developmental instability that has been hypothesized to be inversely correlated with heterozygosity. Although this claim has been widely repeated, several studies have reported no such association. Therefore, we test the generality of this association, using meta-analysis, by converting test statistics for the relationship between heterozygosity (H) and Fluctuating Asymmetry (FA) into a common effect size, the Pearson’s product-moment correlation coefficient. We have analysed a database containing 41 studies with a total of 118 individual samples. Overall we found an unweighted mean negative effect size; r =−0.09 (i.e. a negative correlation between H and FA). Significant heterogeneity in effect size was mainly caused by a difference between ectothermic and endothermic animals, and to a lesser extent by the use of different study designs (i.e. within-population vs. among-populations). Mean effect size for endothermic animals was positive and significantly different from the mean effect size for ectothermic animals. Only for within-population studies of ectothermic animals did we find a significantly negative effect size ( r =−0.23 ± 0.09). The distribution of effect sizes in relation to sample size provided little evidence for patterns typical of those produced by publication bias. Our analysis suggests, at best, only a weak association between H and FA, and heterozygosity seems to explain only a very small amount of the variation in developmental instability among individuals and populations ( r ^2=0.01 for the total material).
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sexual selection in the barn swallow hirundo rustica iv patterns of Fluctuating Asymmetry and selection against Asymmetry
Evolution, 1994Co-Authors: Anders Pape MollerAbstract:-The patterns of variation in Fluctuating Asymmetry were studied in four morphological characters of the barn swallow Hirundo rustica. The level of absolute and relative Asymmetry was larger in the secondary sexual character "outer tail length" than in three nonsexual morphological traits (wing, central tail, and tarsus length). The extent of individual Asymmetry in outer tail length was negatively correlated with tail-ornament size, whereas the relationship between Asymmetry of all other morphological characters and their size was flat or U-shaped. Asymmetry in outer tail length was unrelated to Asymmetry in other morphological characters, whereas asymmetries in the length of wing, central tail, and tarsus were positively correlated. Male barn swallows exhibited larger Asymmetry in outer tail length than females. Asymmetry of most morphological traits exhibited intermediate repeatabilities between years, with the exception of male and female outer tail length, which were highly repeatable. Tail Asymmetry of offspring weakly, though significantly, resembled that of their parents. Asymmetry in wing and outer tail length was also significantly related to several fitness components. Male barn swallows that acquired a mate were less asymmetric in wing and outer tail length than unmated males. Females with more asymmetrical tails laid eggs significantly later. Annual reproductive success was unrelated to Fluctuating Asymmetry. Male barn swallows that survived were less asymmetric in wing and outer tail length than nonsurvivors, whereas female survivors were less asymmetric in outer tail length than nonsurvivors. These results suggest that levels of Fluctuating Asymmetry in barn swallows are associated with differences in fitness.
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Fluctuating Asymmetry and sexual selection
Genetica, 1993Co-Authors: Anders Pape Moller, Andrew PomiankowskiAbstract:Fluctuating Asymmetry occurs when an individual is unable to undergo identical development on both sides of a bilaterally symmetrical trait. Fluctuating Asymmetry measures the sensitivity of development to a wide array of genetic and environmental stresses. We propose that Fluctuating Asymmetry is used in many signalling contexts for assessment of an individual's ability to cope with its environment. We hypothesize that Fluctuating Asymmetry is used in sexual selection, both in fighting and mate choice, and in competition for access to resources. Evidence is reviewed showing that the patterns of Fluctuating Asymmetry in secondary sexual characters differ from those seen in other morphological traits. Secondary sexual characters show much higher levels of Fluctuating Asymmetry. Also, there is often a negative relationship between Fluctuating Asymmetry and the absolute size of ornaments, whereas the relationship is typically U-shaped in other morphological traits. The common negative relationship between Fluctuating Asymmetry and ornament size suggests that many ornaments reliably reflect individual quality.
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parasites differentially increase the degree of Fluctuating Asymmetry in secondary sexual characters
Journal of Evolutionary Biology, 1992Co-Authors: Anders Pape MollerAbstract:The degree of Fluctuating Asymmetry has been demonstrated to reflect the ability of individuals to cope with different kinds of environmental stress (Parsons 1990). Parasites and diseases are one kind of environmental stress which most individuals encounter during their lifetime. Parasites have also been suggested to play an important role in sexual selection and the development of ornaments, since the full expression of ornaments may reflect the ability of hosts to cope with the debilitating effects of parasites. Here I report for the first time that a parasite, the haematophagous tropical fowl mite Ornithonyssus bursa (Macronyssidae, Gamasida), directly affects the degree of Fluctuating Asymmetry in a secondary sexual character of its host, the elongated tail of the swallow Hirundo rustica (Aves: Hirundinidae). I experimentally manipulated the mite load of swallow nests during one season by either increasing or reducing the number of mites, or keeping nests as controls. The degree of Fluctuating Asymmetry was measured in the subsequent year after the swallows had grown new tail ornaments under the altered parasite regime. The degree of Fluctuating Asymmetry was larger at increasing levels of parasites for male tail length, but not for the length of the shortest tail feather or wing length or for tail and wing length in females. These results suggest that the degree of Fluctuating Asymmetry in tail ornaments, but not in other feather traits, reliably reveals the level of parasite infestation. This has important implications for the ability of conspecifics to use the size and the expression of ornaments in assessment of phenotypic quality and thus in sexual selection.
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patterns of Fluctuating Asymmetry in weapons evidence for reliable signalling of quality in beetle horns and bird spurs
Proceedings of The Royal Society B: Biological Sciences, 1992Co-Authors: Anders Pape MollerAbstract:Fluctuating Asymmetry is an epigenetic measure of the ability of individuals to undergo identical development of a usually bilaterally symmetrical character on both sides of the body. Horns of beetles and spurs of birds are elaborate structures usually restricted to or enlarged in individuals of the limited sex and frequently used in intrasexual combat. Individuals with large horns usually win fights against individuals with small horns which suggests that horn size may reliably signal male fighting ability. A comparative study of the patterns of Fluctuating Asymmetry in horns of beetles and spurs of birds showed that the degree of Asymmetry in these secondary sex traits was considerably larger than in elytra and wing length, which are apparently not subjected to sexual selection. There was a negative relationship between the degree of Asymmetry and size of the secondary sex trait while the relationship for elytra and wing length was flat or U-shaped. This demonstrates that horn and spur size may reliably reflect male quality as determined by the degree of Fluctuating Asymmetry.
Dan Cogălniceanu - One of the best experts on this subject based on the ideXlab platform.
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Using digital images in the study of Fluctuating Asymmetry in the spur-thighed tortoise Testudo graeca
TURKISH JOURNAL OF ZOOLOGY, 2013Co-Authors: Gabriel Buică, Dan CogălniceanuAbstract:Fluctuating Asymmetry has been proposed as a useful noninvasive tool for detecting the influence of the environment on body development. In the present study, we used digital images to estimate the Fluctuating Asymmetry of the plastron in an isolated Testudo graeca population in Dobrogea, Romania. We extracted data from the photos regarding the area, height, and width of 3 plastron scutes. A total of 155 adult tortoises analysed showed reduced variation in plastron Asymmetry and no significant relationship was detected between Fluctuating Asymmetry and sex or body size. We suggest that Fluctuating Asymmetry may be an individual trait, with no predictive value at the population level.
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Fluctuating Asymmetry in the Eurasian Spur-Thighed Tortoise, Testudo graeca ibera Linneaus, 1758 (Testudines: Testudinidae)
Chelonian Conservation and Biology, 2012Co-Authors: Raluca Ioana Băncilă, Rodica Plăiaşu, Marian Tudor, Ciprian Samoilă, Dan CogălniceanuAbstract:Abstract We studied plastron-shaped Asymmetry of the Eurasian Spur-Thighed Tortoise, Testudo graeca ibera, as related to life stage, gender, and distribution. Our analyses of 523 individuals showed that Fluctuating Asymmetry (FA) in plastron shape varied with gender (males exhibited higher levels of FA than did females) and across populations, whereas life stage had no significant effect. Although we could not identify the potential sources of variation responsible for the observed patterns of developmental instability, our study shows the value of FA as a method for studies of developmental instability in turtles.
Randy Thornhill - One of the best experts on this subject based on the ideXlab platform.
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jamaican symmetry project long term study of Fluctuating Asymmetry in rural jamaican children
Human Biology, 1999Co-Authors: Robert Trivers, Randy Thornhill, John T Manning, D N Singh, M McguireAbstract:Fluctuating Asymmetry, small deviations from perfect bilateral symmetry, is negatively correlated with health and positively correlated with sexual selection in human adults, but the accumulation, persistence, and fitness implications of asymmetries during childhood are largely unknown. Here, we introduce the Jamaican Symmetry Project, a long-term study of Fluctuating Asymmetry and its physical and behavioral correlates in rural Jamaican children. The project is based on an initial sample of 285 children (156 boys and 129 girls), aged 5 to 11 years. We describe the design of the project and the methodology of measuring 10 paired morphometric traits. All traits except hand width showed Fluctuating Asymmetry. Fluctuating asymmetries of the legs tended to be related and were less than half as great as Fluctuating asymmetries of the arms and ears. Therefore the legs may show high developmental stability resulting from selection for mechanical efficiency. A Fluctuating Asymmetry composite score revealed that boys have significantly lower Fluctuating Asymmetry than girls and that this effect resides mainly in the elbows. There were significant positive relationships between composite Fluctuating Asymmetry and age, height, and weight, but multiple regression analyses showed that age was negatively related to Fluctuating Asymmetry, whereas body size was positively correlated. These findings are compared with results from recent English studies.
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Fluctuating Asymmetry and psychometric intelligence
Proceedings of The Royal Society B: Biological Sciences, 1997Co-Authors: F B Furlow, Steven W Gangestad, T Armijoprewitt, Randy ThornhillAbstract:Little is known about the genetic nature of human psychometric intelligence (IQ), but it is widely assumed that IQ's heritability is at loci for intelligence per se. We present evidence consistent with a hypothesis that interindividual IQ differences are partly due to heritable vulnerabilities to environmental sources of developmental stress, an indirect genetic mechanism for the heritability of IQ. Using Fluctuating Asymmetry (FA) of the body (the Asymmetry resulting from errors in the development of normally symmetrical bilateral traits under stressful conditions), we estimated the relative developmental instability of 112 undergraduates and administered to them Cattell's culture fair intelligence test (CFIT). A subsequent replication on 128 students was performed. In both samples, FA correlated negatively and significantly with CFIT scores. We propose two non-mutually exclusive physiological explanations for this correlation. First, external body FA may correlate negatively with the developmental integrity of the brain. Second, individual energy budget allocations and/or low metabolic efficiency in high-FA individuals may lower IQ scores. We review the data on IQ in light of our findings and conclude that improving developmental quality may increase average IQ in future generations.
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the evolutionary psychology of extrapair sex the role of Fluctuating Asymmetry
Evolution and Human Behavior, 1997Co-Authors: Steven W Gangestad, Randy ThornhillAbstract:Abstract This study explored evolutionary hypotheses concerning extrapair sex (or EPCs: extrapair copulations). Based on recent notions about sexual selection, we predicted that (a) men's number of EPCs would correlate negatively with their Fluctuating Asymmetry, a measure of the extent to which developmental design is imprecisely expressed, and (b) men's number of times having been an EPC partner of a woman would negatively correlate with their Fluctuating Asymmetry. In a sample of college heterosexual couples, both hypotheses were supported. In addition, men's physical attractiveness independently predicted how often they had been an EPC partner. Women's anxious attachment style positively covaried with their number of EPC partners, whereas their avoidant attachment style negatively covaried with their number of EPC partners.
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human female orgasm and mate Fluctuating Asymmetry
Animal Behaviour, 1995Co-Authors: Randy Thornhill, Steven W Gangestad, Randall ComerAbstract:Abstract Human, Homo sapiens , female orgasm is not necessary for conception; hence it seems reasonable to hypothesize that orgasm is an adaptation for manipulating the outcome of sperm competition resulting from facultative polyandry. If heritable differences in male viability existed in the evolutionary past, selection could have favoured female adaptations (e.g. orgasm) that biased sperm competition in favour of males possessing heritable fitness indicators. Accumulating evidence suggests that low Fluctuating Asymmetry is a sexually selected male feature in a variety of species, including humans, possibly because it is a marker of genetic quality. Based on these notions, the proportion of a woman's copulations associated with orgasm is predicted to be associated with her partner's Fluctuating Asymmetry. A questionnaire study of 86 sexually active heterosexual couples supported this prediction. Women with partners possessing low Fluctuating Asymmetry and their partners reported significantly more copulatory female orgasms that were reported by women with partners possessing high Fluctuating Asymmetry and their partners, even with many potential confounding variables controlled. The findings are used to examine hypotheses for female orgasm other than selective sperm retention.
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human Fluctuating Asymmetry and sexual behavior
Psychological Science, 1994Co-Authors: Randy Thornhill, Steven W GangestadAbstract:This report presents evidence that sexual selection may favor developmental stability (i e, the absence of Fluctuating Asymmetry) in humans Subtle, heritable asymmetries in seven nonfacial human body traits correlated negatively with number of self-reported, lifetime sex partners and correlated positively with self-reported age at first copulation in a college student sample These relationships remained statistically significant when age, marital status, body height, ethnicity, physical anomalies associated with early prenatal development, and physical attractiveness were statistically controlled The strength of the relationships did not differ significantly as a function of sex It is unlikely that the relationships are generated by false self-reporting of sexual experience
Steven W Gangestad - One of the best experts on this subject based on the ideXlab platform.
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men s oxidative stress Fluctuating Asymmetry and physical attractiveness
Animal Behaviour, 2010Co-Authors: Steven W Gangestad, Leslie A Merriman, Melissa Emery ThompsonAbstract:Aerobic organisms naturally create reactive oxygen species (ROS) as by-products of energy production. These substances can damage DNA and tissue, and probably are major causes of mutation, ageing and a host of diseases. Oxidative stress occurs when an organism produces an overabundance of ROS relative to ROS-neutralizing antioxidants. In this study, we examined the hypotheses that individual differences in oxidative stress are associated with Fluctuating Asymmetry and with perceived mate quality. We measured urinary biomarkers of oxidative stress (8-hydroxy-2′-deoxyguanosine (8-OHdG) and malondialdehyde (MDA)) in a sample of healthy, young men and tested their association with Fluctuating Asymmetry and physical attractiveness. A composite measure of oxidative stress correlated positively with FA and negatively with physical attractiveness (with exposure to toxins, smoking, and their interaction statistically controlled for). Follow-up analyses yielded associations of oxidative stress with both healthy and masculine appearance. No association was mediated by cortisol or testosterone. These findings may yield insights into previously unidentified factors that affect the development of phenotypic features under sexual selection and contribute to the shape of human life histories, and have potential implications for other species as well.
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Fluctuating Asymmetry sociosexuality and intrasexual competitive tactics
Journal of Personality and Social Psychology, 1999Co-Authors: Jeffry A Simpson, Steven W Gangestad, Niels P Christensen, Kira LeckAbstract:Heterosexual men and women were told they were competing with another same-sex individual for a date with an attractive opposite-sex interviewer. After answering 6 questions, participants were asked to tell the competitor why the interviewer should choose them over the competitor. Participants' videotaped behavior was coded for different behavioral tactics. Men who were more symmetrical and who had a more unrestricted sociosexual orientation were more likely to use direct competition tactics than were less symmetrical and restricted men. Restricted men accentuated their positive personal qualities, presenting themselves as "nice guys." Structural equation modeling revealed that Fluctuating Asymmetry (FA) was directly associated with the use of direct competition tactics. However, the link between FA and presenting oneself as a nice guy was mediated through sociosexuality. No effects were found for women.
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Fluctuating Asymmetry and psychometric intelligence
Proceedings of The Royal Society B: Biological Sciences, 1997Co-Authors: F B Furlow, Steven W Gangestad, T Armijoprewitt, Randy ThornhillAbstract:Little is known about the genetic nature of human psychometric intelligence (IQ), but it is widely assumed that IQ's heritability is at loci for intelligence per se. We present evidence consistent with a hypothesis that interindividual IQ differences are partly due to heritable vulnerabilities to environmental sources of developmental stress, an indirect genetic mechanism for the heritability of IQ. Using Fluctuating Asymmetry (FA) of the body (the Asymmetry resulting from errors in the development of normally symmetrical bilateral traits under stressful conditions), we estimated the relative developmental instability of 112 undergraduates and administered to them Cattell's culture fair intelligence test (CFIT). A subsequent replication on 128 students was performed. In both samples, FA correlated negatively and significantly with CFIT scores. We propose two non-mutually exclusive physiological explanations for this correlation. First, external body FA may correlate negatively with the developmental integrity of the brain. Second, individual energy budget allocations and/or low metabolic efficiency in high-FA individuals may lower IQ scores. We review the data on IQ in light of our findings and conclude that improving developmental quality may increase average IQ in future generations.
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the evolutionary psychology of extrapair sex the role of Fluctuating Asymmetry
Evolution and Human Behavior, 1997Co-Authors: Steven W Gangestad, Randy ThornhillAbstract:Abstract This study explored evolutionary hypotheses concerning extrapair sex (or EPCs: extrapair copulations). Based on recent notions about sexual selection, we predicted that (a) men's number of EPCs would correlate negatively with their Fluctuating Asymmetry, a measure of the extent to which developmental design is imprecisely expressed, and (b) men's number of times having been an EPC partner of a woman would negatively correlate with their Fluctuating Asymmetry. In a sample of college heterosexual couples, both hypotheses were supported. In addition, men's physical attractiveness independently predicted how often they had been an EPC partner. Women's anxious attachment style positively covaried with their number of EPC partners, whereas their avoidant attachment style negatively covaried with their number of EPC partners.
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human female orgasm and mate Fluctuating Asymmetry
Animal Behaviour, 1995Co-Authors: Randy Thornhill, Steven W Gangestad, Randall ComerAbstract:Abstract Human, Homo sapiens , female orgasm is not necessary for conception; hence it seems reasonable to hypothesize that orgasm is an adaptation for manipulating the outcome of sperm competition resulting from facultative polyandry. If heritable differences in male viability existed in the evolutionary past, selection could have favoured female adaptations (e.g. orgasm) that biased sperm competition in favour of males possessing heritable fitness indicators. Accumulating evidence suggests that low Fluctuating Asymmetry is a sexually selected male feature in a variety of species, including humans, possibly because it is a marker of genetic quality. Based on these notions, the proportion of a woman's copulations associated with orgasm is predicted to be associated with her partner's Fluctuating Asymmetry. A questionnaire study of 86 sexually active heterosexual couples supported this prediction. Women with partners possessing low Fluctuating Asymmetry and their partners reported significantly more copulatory female orgasms that were reported by women with partners possessing high Fluctuating Asymmetry and their partners, even with many potential confounding variables controlled. The findings are used to examine hypotheses for female orgasm other than selective sperm retention.
Stefan Van Dongen - One of the best experts on this subject based on the ideXlab platform.
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Fluctuating Asymmetry and sexual dimorphism in human facial morphology a multi variate study
Symmetry, 2021Co-Authors: Omid Ekrami, Peter Claes, Ellen Van Assche, Mark D Shriver, Seth M Weinberg, Mary L Marazita, Susan Walsh, Stefan Van DongenAbstract:(1) Background: Fluctuating Asymmetry is often used as an indicator of developmental instability, and is proposed as a signal of genetic quality. The display of prominent masculine phenotypic features, which are a direct result of high androgen levels, is also believed to be a sign of genetic quality, as these hormones may act as immunosuppressants. Fluctuating Asymmetry and masculinity are therefore expected to covary. However, there is lack of strong evidence in the literature regarding this hypothesis. (2) Materials and methods: In this study, we examined a large dataset of high-density 3D facial scans of 1260 adults (630 males and 630 females). We mapped a high-density 3D facial mask onto the facial scans in order to obtain a high number of quasi-landmarks on the faces. Multi-dimensional measures of Fluctuating Asymmetry were extracted from the landmarks using Principal Component Analysis, and masculinity/femininity scores were obtained for each face using Partial Least Squares. The possible correlation between these two qualities was then examined using Pearson’s coefficient and Canonical Correlation Analysis. (3) Results: We found no correlation between Fluctuating Asymmetry and masculinity in men. However, a weak but significant correlation was found between average Fluctuating Asymmetry and masculinity in women, in which feminine faces had higher levels of Fluctuating Asymmetry on average. This correlation could possibly point to genetic quality as an underlying mechanism for both Asymmetry and masculinity; however, it might also be driven by other fitness or life history traits, such as fertility. (4) Conclusions: Our results question the idea that Fluctuating Asymmetry and masculinity should be (more strongly) correlated in men, which is in line with the recent literature. Future studies should possibly focus more on the evolutionary relevance of the observed correlation in women.
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environmental stress increases skeletal Fluctuating Asymmetry in the moor frog rana arvalis
Oecologia, 2007Co-Authors: Fredrik Soderman, Stefan Van Dongen, Susanna Pakkasmaa, Juha MerilaAbstract:Whether Fluctuating Asymmetry (FA) provides a useful metric indicator of the degree of environmental stress experienced by populations is still a contentious issue. We investigated whether the degr ...
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Fluctuating Asymmetry as an indicator of fitness can we bridge the gap between studies
Biological Reviews, 2002Co-Authors: Luc Lens, Stefan Van Dongen, Salit Kark, Erik MatthysenAbstract:There is growing evidence from both experimental and non-experimental studies that Fluctuating Asymmetry does not consistently index stress or fitness. The widely held ‐ yet poorly substantiated ‐ belief that Fluctuating Asymmetry can act as a universal measure of developmental stability and predictor of stressmediated changes in fitness, therefore staggers. Yet attempts to understand why the reported relationships between Fluctuating Asymmetry, stress and fitness are so heterogeneous ‐ i.e. whether the associations are truly weak or non-existent or whether they become confounded during different stages of the analytical pathways ‐ remain surprisingly scarce. Hence, we attempt to disentangle these causes, by reviewing the various statistical and conceptual factors that are suspected to confound potential relationships between Fluctuating Asymmetry, stress and fitness. Two main categories of factors are discerned: those associated with the estimation of developmental stability through Fluctuating Asymmetry, and those associated with the effects of genotype and environment on developmental stability. Next, we describe a series of statistical tools that have recently been developed to help reduce this noise. We argue that the current lack of a theoretical framework that predicts if and when relationships with developmental stability can be expected, urges for further theoretical and empirical research, such as on the genetic architecture of developmental stability in stressed populations. If the underlying developmental mechanisms are better understood, statistical patterns of Asymmetry variation may become a biologically meaningful tool.
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How repeatable is the estimation of developmental stability by Fluctuating Asymmetry
Proceedings of the Royal Society of London. Series B: Biological Sciences, 1998Co-Authors: Stefan Van DongenAbstract: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.