Showing papers on "Fluctuating asymmetry published in 2021"

Nature, Nurture, and Noise: Developmental Instability, Fluctuating Asymmetry, and the Causes of Phenotypic Variation

Abstract: Phenotypic variation arises from genetic and environmental variation, as well as random aspects of development. The genetic (nature) and environmental (nurture) components of this variation have been appreciated since at least 1900. The random developmental component (noise) has taken longer for quantitative geneticists to appreciate. Here, I sketch the historical development of the concepts of random developmental noise and developmental instability, and its quantification via fluctuating asymmetry. The unsung pioneers in this story are Hugo DeVries (fluctuating variation, 1909), C. H. Danforth (random variation between monozygotic twins, 1919), and Sewall Wright (random developmental variation in piebald guinea pigs, 1920). The first pioneering study of fluctuating asymmetry, by Sumner and Huestis in 1921, is seldom mentioned, possibly because it failed to connect the observed random asymmetry with random developmental variation. This early work was then synthesized by Boris Astaurov in 1930 and Wilhelm Ludwig in 1932, and then popularized by Drosophila geneticists beginning with Kenneth Mather in 1953. Population phenogeneticists are still trying to understand the origins and behavior of random developmental variation. Some of the developmental noise represents true stochastic behavior of molecules and cells, while some represents deterministic chaos, nonlinear feedback, and symmetry breaking.

Self-Perceived Facial Attractiveness, Fluctuating Asymmetry, and Minor Ailments Predict Mental Health Outcomes

Abstract: Phenotypic markers associated with developmental stability such as fluctuating asymmetry, facial attractiveness, and reports of minor ailments can also act as indicators of overall physical health. However, few studies have assessed whether these markers might also be cues of mental health. We tested whether self- and other-perceived facial attractiveness, fluctuating asymmetry, and minor ailments are associated with psychopathological symptoms in a mixed sample of 358 college students, controlling for the effects of body mass index, age, and sex. We applied the Symptom Checklist-90-Revised (SCL-90-R) questionnaire to assess psychopathological symptoms, a battery of questionnaires about self-perceptions of facial attractiveness, and gathered information about the number of previous minor ailments as well as demographic data. Other-perceived attractiveness was assessed by an independent mixed sample of 109 subjects. Subjects’ facial fluctuating asymmetry was determined by geometric morphometrics. The results revealed that in both men and women, higher self-perceived attractiveness and fewer minor ailments predicted lower scores of Somatization, Obsessive–Compulsive, Interpersonal Sensitivity, Depression, Anxiety, Phobic Anxiety, Paranoid Ideation, Psychoticism, and a General Psychopathology Index. Higher facial fluctuating asymmetry was associated with higher Interpersonal Sensitivity, but did not contribute to its prediction when controlling for the other studied variables. The observed strong associations between self-perceived attractiveness, minor ailments, and psychopathology indicate common developmental pathways between physiological and psychological symptomatology which may reflect broader life history (co)variation between genetics, developmental environment, and psychophysiological functioning.

Exploring directional and fluctuating asymmetry in the human palate during growth

Abstract: OBJECTIVES Palate morphology is constantly changing throughout an individual's lifespan, yet its asymmetry during growth is still little understood. In this research, we focus on the study of palate morphology by using 3D geometric morphometric approaches to observe changes at different stages of life, and to quantify the impact of directional and fluctuating asymmetry on different areas at different growth stages. MATERIALS AND METHODS The sample consists of 183 individuals (1-72 years) from two identified human skeletal collections of 19th and early 20th Century Italian contexts. A 3D-template of 41 (semi)landmarks was applied on digital palate models to observe morphological variation during growth. RESULTS Asymmetrical components of the morphological structure appears multidirectional on the entire palate surface in individuals <2 years old and become oriented (opposite bilateral direction) between 2 and 6 years of age. Specifically, directional asymmetry differentially impacts palate morphology at different stages of growth. Both the anterior and posterior palate are affected by mild alterations in the first year of life, while between 2 and 6 years asymmetry is segregated in the anterior area, and moderate asymmetry affects the entire palatal surface up to 12 years of age. Our results show that stability of the masticatory system seems to be reached around 13-35 years first by females and then males. From 36 years on both sexes show similar asymmetry on the anterior area. Regarding fluctuating asymmetry, inter-individual variability is mostly visible up to 12 years of age, after which only directional trends can be clearly observed at a group level. DISCUSSION Morphological structure appears instable during the first year of life and acquires an opposite asymmetric bilateral direction between 2 and 6 years of age. This condition has been also documented in adults; when paired with vertical alteration, anterior/posterior asymmetry seems to characterize palate morphology, which is probably due to mechanical factors during the lifespan. Fluctuating asymmetry is predominant in the first period of life due to a plausible relationship with the strength of morphological instability of the masticatory system. Directional asymmetry, on the other hand, shows that the patterning of group-level morphological change might be explained as a functional response to differential inputs (physiological forces, nutritive and non-nutritive habits, para-masticatory activity as well as the development of speech) in different growth stages. This research has implications with respect to medical and evolutionary fields. In medicine, palate morphology should be considered when planning orthodontic and surgical procedures as it could affect the outcome. As far as an evolutionary perspective is concerned the dominance of directional asymmetries in the masticatory system could provide information on dietary and cultural habits as well as pathological conditions in our ancestors.

Early life malnutrition and fluctuating asymmetry in the rat bony labyrinth

Abstract: Maternal malnutrition during gestation and lactation is known to have adverse effects on offspring. We evaluate the impact of maternal diet on offspring bony labyrinth morphology. The bony labyrinth develops early and is thought to be stable to protect vital sensory organs within. For these reasons, bony labyrinth morphology has been used extensively to assess locomotion, hearing function, and phylogeny in primates and numerous other taxa. While variation related to these parameters has been documented, there is still a component of intraspecific variation that is unexplained. Although the labyrinthine developmental window is small, it may provide the opportunity for developmental instability to produce corresponding shape differences, as measured by fluctuating asymmetry (FA). We hypothesized that (a) offspring with poor maternal diet would exhibit increased FA, but (b) no unilateral shape difference. To test these hypotheses, we used two groups of rats (Rattus norvegicus; Crl:WI[Han] strain), one control group and one group exposed to a isocaloric, protein-restricted maternal diet during gestation and suckling. Individuals were sampled at weaning, sexual maturity, and old age. A Procrustes analysis of variance identified statistically significant FA in all diet-age subgroups. No differences in level of FA were identified among the subgroups, rejecting our first hypothesis. A principal components analysis identified no unilateral shape differences, supporting our second hypothesis. These results indicate that bony labyrinth morphology is remarkably stable and likely protected from a poor maternal diet during development. In light of this result, other factors must be explored to explain intraspecific variation in labyrinthine shape.

Fluctuating Asymmetry and Sexual Dimorphism in Human Facial Morphology: A Multi-Variate Study

Abstract: (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

A Pre-registered Meta-analysis Based on Three Empirical Studies Reveals No Association Between Prenatal (Amniotic) Cortisol Exposure and Fluctuating Asymmetry in Human Infants

Abstract: Developmental instability (DI) reflects an organism’s inability to develop an ideal phenotype when challenged by genetic and environmental insults. DI can be estimated via the proxy measure of fluctuating asymmetry (FA), i.e., the small random deviations from perfect bilateral symmetry observed in the morphology of paired traits. The mechanisms involved in the genesis of FA in human populations are relatively unknown, though animal research indicates that hormonal processes may be involved. As maternal stress during pregnancy is detrimental to various developmental processes, elevated prenatal cortisol may represent a causal factor in the subsequent emergence of an asymmetrical phenotype. The main purpose of this pre-registered meta-analysis based on three empirical studies was to investigate whether mid-trimester amniotic cortisol levels predict subsequent FA in finger lengths of infants from Germany, Portugal, and the UK. No statistically significant relationships were observed, and meta-analytic combination of the effect size estimates yielded a null result. We did, however, detect significant positive correlations between the cortisol present in the amniotic fluid and maternal plasma in the Portuguese cohort, and observed that FA in the German cohort was significantly lower at 70-months than at either 9- or 20-months. Taken together, the current findings run contrary to animal research showing that elevated prenatal corticosterone exposure leads to increased FA. However, this may be because a single cortisol assay obtained via amniocentesis is an inadequate proxy for average gestational exposure, and/or that prenatal cortisol levels at an earlier (i.e., first rather than second trimester) stage of pregnancy is what explains variance in subsequent FA.

Fluctuating asymmetry, a marker of poor growth quality, is associated with adult male metabolic rate.

Abstract: Objectives Life history theory, a branch of evolutionary theory, predicts the existence of trade-offs in energetic allocation between competing physiological functions. The core metabolic cost of self-maintenance, measured by resting metabolic rate (RMR), represents a large component of human daily energy expenditure. Despite strong selective pressures for energetic frugality and high observed interindividual variation in RMR, the link between RMR and energetic allocation to life-history traits remains understudied in humans. Materials In a sample of 105 (m = 57, f = 48), we investigated the relationship between adult RMR and investment in growth quality, as measured by fluctuating asymmetry (FA). Results Measurement of RMR and FA in university rowers revealed a significant positive correlation amongst males (n = 57, r = 0.344, p = 0.005, 1-tailed; standardized 95% CI, 0.090 to 0.598). Convincing evidence for a correlation among females was not found (n = 48, r = 0.142, p = 0.169, 1-tailed, standardized 95% CI, -0.152 to 0.435). Discussion The data suggest that low-quality asymmetrical growth is associated with later-life metabolic inefficiencies in males. Energetic investment in processes (likely concerning the stress-response) unrelated to growth during childhood may thereby trade-off against adult metabolic efficiency. We suggest that the presence of a relationship between RMR and FA in males but not females may be explained by the additional metabolic strain associated with larger body size and increased male muscularity, which may amplify the inefficiencies arising from low-quality growth.

The Fluctuating Asymmetry of the Butterfly Wing Pattern Does Not Change along an Industrial Pollution Gradient

Abstract: The rapid and selective responses to changes in habitat structure and climate have made butterflies valuable environmental indicators. In this study, we asked whether the decline in butterfly populations near the copper-nickel smelter in Monchegorsk in northwestern Russia is accompanied by phenotypic stress responses to toxic pollutants, expressed as a decrease in body size and an increase in fluctuating asymmetry. We measured the concentrations of nickel and copper, forewing length, and fluctuating asymmetry in two elements of wing patterns in Boloria euphrosyne, Plebejus idas, and Agriades optilete collected 1–65 km from Monchegorsk. Body metal concentrations increased toward the smelter, confirming the local origin of the collected butterflies. The wings of butterflies from the most polluted sites were 5–8% shorter than those in unpolluted localities, suggesting adverse effects of pollution on butterfly fitness due to larval feeding on contaminated plants. However, fluctuating asymmetry averaged across two hindwing spots did not change systematically with pollution, thereby questioning the use of fluctuating asymmetry as an indicator of habitat quality in butterfly conservation projects.

Fluctuating Asymmetry and Stress in Macaca fuscata: Does Captivity Affect Morphology?

Abstract: Fluctuating Asymmetry (FA) in morphology is used as a proxy for developmental instability in response to stress factors. FA has important implications for understanding the impact of differential environments and stressors on the skeletal phenotype. Here, we explore FA in the mandibular morphology of wild and captive Macaca fuscata to detect differences induced by the captive environment. We use two different approaches in Geometric Morphometrics to characterise the degree and patterns of FA and Directional Asymmetry (DA) based on 3D mandibular landmarks. Our results show that the wild and captive groups exhibit morphological dissimilarities in the symmetric component of shape while no significant degree of asymmetry (fluctuating or directional) was detected. Based on our results and on previous literature on the subject, we suggest that (I) captivity is likely to affect the mandibular morphology of M. fuscata; (II) FA may not be a suitable indicator to detect stress in the conditions analysed; and that (III) the mandible may not be the ideal region to study asymmetry because of its functional nature.

Evaluation of fluctuating asymmetry and sexual dimorphism of Channa striata using landmark-based geometric morphometric analysis from Agusan Marsh and Lake Mainit in Caraga Region, Philippines

Abstract: . Saura EBD, Falcasantos GC, Andante RJM, Munda LC, Alimorong MM, Hernando BJ. 2021. Evaluation of fluctuating asymmetry and sexual dimorphism of Channa striata using landmark-based geometric morphometric analysis from Agusan Marsh and Lake Mainit in Caraga Region, Philippines. Nusantara Bioscience 13: 100-110. Evaluation was conducted to determine the impact of ecological condition to Channa striata using fluctuating asymmetry (FA) employing the landmark-based geometric morphometric analysis, using TPS software, SAGE, PAST-Hotellings Test, including Physico-chemical analysis, cyanide and four base metals. Results of Physico-chemical analysis of the two habitats showed Agusan marsh with low oxygen level (3.37-4.55) and high in Iron and TDS as compared to DENR Standards. The statistical results showed high variations (p < 0.0001) on left and right-side having percentage of 79.22% in Agusan Marsh and 72.35% in Lake Mainit which is relatively high Fluctuating Asymmetry. In terms of sex, Agusan marsh had 84.27% and 85.41% FA in males and females while Lake Mainit having 85.12% and 80.89% in males and females. The fairly similar percentage of Fluctuating Asymmetry confirms no sexual dimorphism and no shape differences between male and female, and no peculiar characters to distinguished between sexes based on the 17 landmark points. Present study concluded that FA observed in the snout tip was due to breeding behavior, the landmark points in cephalic, pectoral, and caudal region were associated with burrowing and mobility factors within the lateral line system in these fishes which thrive in high turbid habitat and low oxygen. Furthermore, it was found that the level of FA tends to increase in disturbed environs.

Assessments of bilateral asymmetry with application in human skull analysis.

Abstract: As a common feature, bilateral symmetry of biological forms is ubiquitous, but in fact rarely exact. In a setting of analytic geometry, bilateral symmetry is defined with respect to a point, line or plane, and the well-known notions of fluctuating asymmetry, directional asymmetry and antisymmetry are recast. A meticulous scheme for asymmetry assessments is proposed and explicit solutions to them are derived. An investigation into observational errors of points representing the geometric structure of an object offers a baseline reference for asymmetry assessment of the object. The proposed assessments are applicable to individual, part or all point pairs at both individual and collective levels. The exact relationship between the developed treatments and the widely used Procrustes method in asymmetry assessment is examined. An application of the proposed assessments to a large collection of human skull data in the form of 3D landmark coordinates finds: (a) asymmetry of most skulls is not fluctuating, but directional if measured about a plane fitted to shared landmarks or side landmarks for balancing; (b) asymmetry becomes completely fluctuating if one side of a skull could be slightly rotated and translated with respect to the other side; (c) female skulls are more asymmetric than male skulls. The methodology developed in this study is rigorous and transparent, and lays an analytical base for investigation of structural symmetries and asymmetries in a wide range of biological and medical applications.

Does fluctuating asymmetry of wing traits capture relative environmental stress in a lepidopteran

Abstract: Fluctuating asymmetry (FA) is hypothesized to be a useful predictor of population canalization, especially for organisms at risk from environmental change.Identification of traits that meet statistical criteria as FA measures remains a challenge.Here, a laboratory experiment subjected immature butterflies (Vanessa cardui) to diet and temperature conditions of varying stress levels. Variation in dietary macronutrient ratio (protein: carbohydrate) and rearing temperature (optimal: 25°C; elevated: 32°C) was introduced as stressors. Temperature and nutrition are key variables influencing ectotherm growth and fitness and so are likely to be important stressors that influence FA.Individuals subjected to stressful conditions were predicted to show elevated FA of three wing size traits, as well as increased mortality and decreased adult body size.Trait FA did not vary across treatments. Instead, treatment levels impacted viability: The combined incidence of pupal death and expression of significant wing malformations increased in treatment levels designated as stressful. Variation in adult dry mass also reflected predicted stress levels. Results suggest that individuals predicted to display increased FA either died or displayed gross developmental aberrations.This experiment illustrates important constraints on the investigation of FA, including selection of appropriate traits and identification of appropriate levels of stressors to avoid elevated mortality. The latter concern brings into question the utility of FA as an indicator of stress in vulnerable, natural populations, where stress levels cannot be controlled, and mortality and fitness effects are often not quantifiable.

Bilateral Asymmetry and Shape of Lamina Plantago major L

Abstract: The aim of the work was to answer the question whether pollution by vehicles and the geographical location of populations affect the asymmetry and shape of the leaf plate Plantago major. The Generalized Procrustes Analysis was provided and the difference in the variance of paired landmarks was indicated. Based on vector coordinates, the symmetry and asymmetry covariance matrices of two types were created, and canonical covariance analysis was performed. The difference was found using the distances between the centers of the coordinate sets, the so-called Mahalanobis distances. The overall pool of leaves showed the presence of fluctuating asymmetry at the level of leaf blades in roadside populations. In the control, a mixture of two types of asymmetry: fluctuating and directional was traced. Canonical variation analysis showed the difference between the center of sets (p <0.0001). A correlation was obtained between the symmetric and asymmetric components of the shape. An allometric ratio of size/asymmetry and size/shape of the sheet plate were not obtained. The decrease in the number of landmarks from 52 to 26 did not affect the results. Thus motor transport, as shown by most of the samples (4 out of 6), had a significant impact on both the shape and asymmetry of the leaf blades. The geographical difference also affected both type of variability, as the difference in the asymmetry and shape of the plantain leaf blades increased over the geographical extent from Vladimir to Moscow on a distance about 200km.

A recent invasive population of the European starling sturnus vulgaris has lower genetic diversity and higher fluctuating asymmetry than primary invasive and native populations

Abstract: Fluctuating asymmetries (FA) are small stress-induced random deviations from perfect symmetry that arise during the development of bilaterally symmetrical traits. One of the factors that can reduce developmental stability of the individuals and cause FA at a population level is the loss of genetic variation. Populations of founding colonists frequently have lower genetic variation than their ancestral populations that could be reflected in a higher level of FA. The European starling (Sturnus vulgaris) is native to Eurasia and was introduced successfully in the USA in 1890 and Argentina in 1983. In this study, we documented the genetic diversity and FA of starlings from England (ancestral population), USA (primary introduction) and Argentina (secondary introduction). We predicted the Argentinean starlings would have the highest level of FA and lowest genetic diversity of the three populations. We captured wild adult European starlings in England, USA, and Argentina, measured their mtDNA diversity and allowed them to molt under standardized conditions to evaluate their FA of primary feathers. For genetic analyses, we extracted DNA from blood samples of individuals from Argentina and USA and from feather samples from individuals from England and sequenced the mitochondrial control region. Starlings in Argentina showed the highest composite FA and exhibited the lowest haplotype and nucleotide diversity. The USA population showed a level of FA and genetic diversity similar to the native population. Therefore, the level of asymmetry and genetic diversity found among these populations was consistent with our predictions based on their invasion history.

Studying factors influencing facial developmental instability.

Abstract: Background: Developmental instability is a component of non-genetic variation that results from random variation in developmental processes. It is considered a sensitive indicator of the physiological state of individuals. It is reflected in various ways, but in this study we focussed on its reflection in fluctuating asymmetry (FA) and morphological integration. Aim: To assess how, if at all, variations of facial morphology mirror developmental instability across childhood with respect to sex, growth rate and socioeconomic/environmental factors. Subjects and methods: A set of 210 three-dimensional facial models (of children aged between 6.3 and 14.3 years) originating from the FIDENTIS 3D Face Database was subjected to landmark-based methods of geometric morphometrics to quantify the degree of facial asymmetry and facial morphological integration. In addition, the association with age, sex, and socioeconomic factors was assessed. Results: Our results showed a nonlinear increase of FA with age up to the age of 14 years. The pattern of sex-related variants in facial FA differed in relation to age, as girls exhibited higher values of FA than boys up to the age of 9 years. We found that a signal of modularity based on functional demands and organisation of the face is of particular importance. Here, girls exhibited higher morphological covariation among modules. During more rapid adolescence-related growth, however, covariation among modules at the asymmetrical level decreased in both sexes. Conclusion: We can conclude that facial morphology was shown to be strongly integrated, particularly until adolescence. This covariation can facilitate an increase of FA. In addition, the results of this study indicate there is a weak association between socioeconomic stress and facial asymmetries. In contrast, sex and growth rate are reflected in developmental instability.

A New Integrated Tool to Calculate and Map Bilateral Asymmetry on Three-Dimensional Digital Models

Abstract: The observation and the quantification of asymmetry in biological structures are deeply investigated in geometric morphometrics. Patterns of asymmetry were explored in both living and fossil species. In living organisms, levels of directional and fluctuating asymmetry are informative about developmental processes and health status of the individuals. Paleontologists are primarily interested in asymmetric features introduced by the taphonomic process, as they may significantly alter the original shape of the biological remains, hampering the interpretation of morphological features which may have profound evolutionary significance. Here, we provide a new R tool that produces the numerical quantification of fluctuating and directional asymmetry and charts asymmetry directly on the specimens under study, allowing the visual inspection of the asymmetry pattern. We tested this show.asymmetry algorithm, written in the R language, on fossil and living cranial remains of the genus Homo. show.asymmetry proved successful in discriminating levels of asymmetry among sexes in Homo sapiens, to tell apart fossil from living Homo skulls, to map effectively taphonomic distortion directly on the fossil skulls, and to provide evidence that digital restoration obliterates natural asymmetry to unnaturally low levels.

Fluctuating Asymmetry Increases with Heat Stress Disruptions on Bali Cattle (Bos javanicus) at Different Altitude

Abstract: Bali cattle ( Bos javanicus ) are common species distributed throughout Indonesia to survive in tropical hot, and humid climates. Fluctuating asymmetry (FA) is a random deviation from perfect bilateral symmetry. FA is often used to measure developmental stability in individuals and can be used as a marker for the impact of environmental and genetic stress. This study aims to investigate the pattern of developmental instability in Bali cattle as caused by environmental stress at various altitudes using the FA index. FA indexes in this study were used to compare asymmetrical physical traits of Bali cattle in Sembalun high altitude and Serading low altitude. Sixty-five Bali cattle were used in this study reared at different altitudes, namely Serading, Sumbawa Island (50 m above sea level), and Sembalun, Lombok Island (1,186 m above sea level). The physical traits of Bali cattle measured were horn circumference (horn), a distance of hip to spine bone (pelvic), metatarsal circumference (metatarsal), and metacarpal circumference (metacarpal). The FA1 and FA5 indexes showed significant metacarpal differences between Bali cattle reared at Sembalun and Serading population (P<0.05). FA11 multiple trait index as a composite of all traits revealed a significant difference as well. (P<001). It can be concluded that various heat stress by altitude impacts the asymmetry of Bali cattle.

Does stress mess with rodents' heads? Influence of habitat amount and genetic factors in mandible fluctuating asymmetry in South American water rats (Nectomys squamipes, Sigmodontinae) from Brazilian Atlantic rainforest remnants.

Abstract: Loss of developmental stability can lead to deviations from bilateral symmetry (i.e. Fluctuating Asymmetry - FA), and is thought to be caused by environmental and genetic factors associated with habitat loss and stress. Therefore, levels of FA might be a valuable tool to monitor wild populations if FA serves as an indicator of exposure to stress due to impacts of habitat loss and fragmentation. In studies examining FA and habitat fragmentation, FA levels are often explained by loss of genetic variation, though few studies have addressed FA's use as indicator of environmental impact. Here, we investigated whether habitat loss, genetic variation, and/or inbreeding affect the developmental instability in Brazilian Atlantic forest populations of a Neotropical water rat (Nectomys squamipes). We sampled individuals from eight sites within Atlantic forest remnants with different amounts of available forest habitat and assessed FA levels with geometric morphometric techniques using adult mandibles. We used observed heterozygosity (Ho) and inbreeding coefficient (Fis), from seven microsatellite markers, as a proxy of genetic variation at individual and population levels. Populations were not significantly different for shape or size FA levels. Furthermore, interindividual variation in both shape and size FA levels and interpopulational differences in size FA levels were best explained by chance. However, habitat amount was negatively associated with both interpopulational variance and average shape FA levels. This association was stronger in populations living in areas with <28% of forest cover, which presented higher variance and higher average FA, suggesting that Nectomys squamipes might have a tolerance threshold to small availability of habitat. Our work is one of the first to use FA to address environmental stress caused by habitat loss in small mammal populations from a Neotropical biome. We suggest that shape FA might serve as a conservation tool to monitor human impact on natural animal populations.

Developmental instability in domesticated mammals.

Abstract: Measures of fluctuating asymmetry (FA) have been adopted widely as an estimate of developmental instability. Arising from various sources of stress, developmental instability is associated with an organism's capacity to maintain fitness. The process of domestication has been framed as an environmental stress with human-specified parameters, suggesting that FA may manifest to a larger degree among domesticates compared to their wild relatives. This study used three-dimensional geometric morphometric landmark data to (a) quantify the amount of FA in the cranium of six domestic mammal species and their wild relatives and, (b) provide novel assessment of the commonalities and differences across domestic/wild pairs concerning the extent to which random variation arising from the developmental system assimilates into within-population variation. The majority of domestic mammals showed greater disparity for asymmetric shape, however, only two forms (Pig, Dog) showed significantly higher disparity as well as a higher degree of asymmetry compared to their wild counterparts (Wild Boar, Wolf). Contra to predictions, most domestic and wild forms did not show a statistically significant correspondence between symmetric shape variation and FA, however, a moderate correlation value was recorded for most pairs (r-partial least squares >0.5). Within pairs, domestic and wild forms showed similar correlation magnitudes for the relationship between the asymmetric and symmetric components. In domesticates, new variation may therefore retain a general, conserved pattern in the gross structuring of the cranium, whilst also being a source for response to selection on specific features.

Fluctuating asymmetry in the insular population of ayu, Plecoglossus altivelis ryukyuensis, estimating its genetic diversity at extinction

Abstract: The present study tested the hypothesis that whether limited genetic diversity was the main factor that led the Ryukyu-ayu population on Okinawa-jima Island to extinction in the late 1970s. The usability of fluctuating asymmetry (FA) in reflecting genetic diversity was tested using two extant populations of Ryukyu-ayu on Amami-oshima Island, then used to estimate genetic diversity for the extinct population which only formalin-preserved specimens are available. The results showed that higher FA indices were associated with lower genetic diversity in the two extant populations, and the extinct population on Okinawa-jima Island had lower FA indices than the two extant populations on Amami-oshima Island. This finding suggests that the genetic diversity of the extinct population was not low enough as to cause its extinction.

Developmental instability and phenotypic evolution in a small and isolated bear population.

Abstract: We explored fluctuating asymmetry (FA) and morphological integration (MI) in the skull of the small, highly inbred and divergent Apennine bear (Ursus arctos marsicanus), to explore its uniqueness a...

A fungal parasite selects against body size but not fluctuating asymmetry in Swiss subalpine yellow dung flies

Abstract: Evidence for selective disadvantages of large body size remains scarce in general. Previous studies of the yellow dung fly Scathophaga stercoraria have demonstrated strong positive sexual and fecundity selection on male and female size. Nevertheless, the body size of flies from a Swiss study population has declined by ~10% 1993–2009. Given substantial heritability of body size, this negative evolutionary response of an evidently positively selected trait suggests important selective factors being missed. An episodic epidemic outbreak of the fungus Entomophthora scatophagae permitted assessment of natural selection exerted by this fatal parasite. Fungal infection varied over the season from ~50% in the cooler and more humid spring and autumn to almost 0% in summer. The probability of dying from fungal infection increased with adult fly body size. Females never laid any eggs after infection, so there was no fungus effect on female fecundity beyond its impact on mortality. Large males showed their typical mating advantage in the field, but this positive sexual selection was nullified by fungal infection. Mean fluctuating asymmetry of paired appendages (legs, wings) did not affect the viability, fecundity or mating success of yellow dung flies in the field. This study documents rare parasite-mediated disadvantages of large-sized flies in the field. Reduced ability to combat parasites such as Entomophthora may be an immunity cost of large body size in dung flies, although the hypothesized trade-off between fluctuating asymmetry, a presumed indicator of developmental instability and environmental stress, and immunocompetence was not found here.

Male sterility significantly elevates shape variation and fluctuating asymmetry of zygomorphic corolla in gynodioecious Glechoma hederacea (Lamiaceae).

Abstract: Female flowers of gynodioecious plants usually have smaller corollas than bisexual flowers. This difference is explained as a developmental consequence of stamen abortion and as a result of stronger selection for larger corolla size in hermaphroditic flowers that solely ensure male function within populations. This study evaluated whether the size difference of zygomorphic corollas in a widely distributed gynodioecious herb Glechoma hederacea is accompanied by variation in shape and bilateral fluctuating asymmetry of sexually differentiated flowers. Geometric morphometric analyses of bilateral symmetry in the shapes of corolla lower lips showed that male-sterile flowers were significantly more plastic and asymmetric, implying that they may be subjected to weaker stabilizing selection for corolla shape in comparison to hermaphrodites. These results illustrated that sexual differentiation may be an important factor contributing to bilateral fluctuating asymmetry in the shape of zygomorphic flowers.

Effect of urbanization and its environmental stressors on the intraspecific variation of flight functional traits in two bumblebee species

Abstract: The way urbanization shapes the intraspecific variation of pollinator functional traits is little understood. However, this topic is relevant for investigating ecosystem services and pollinator health. Here, we studied how urbanization affects the functional traits of workers in two bumblebee species (Bombus terrestris and B. pascuorum) sampled in 37 sites along a gradient of urbanization in North Italy (an area of 1800 km2 including the metropolitan context of Milan and other surrounding capital districts). Namely, we investigated the role played by land-use composition, configuration, temperature, flower resource abundance, and air pollutants on the variation of traits related to flight performance (i.e., body size, wing shape and size fluctuating asymmetry). These traits are relevant because they are commonly used as indicators of stress during insect development. The functional traits of the two bumblebees responded idiosyncratically to urbanization. Urban temperatures were associated with smaller wing sizes in B. pascuorum and with more accentuated fluctuating asymmetry of wing size in B. terrestris. Moreover, flower abundance correlated with bigger wings in B. terrestris and with less asymmetric wing sizes in B. pascuorum. Other traits did not vary significantly and other urban variables played minor effects. These patterns highlight that environmental stressors linked to urbanization negatively impact traits related to flight performance and development stability of these species with possible consequences on the pollination service they provide. Overall, this study found species-specific variation patterns in syntopic taxa, expanding our understanding about the effects of anthropic disturbance in shaping relevant functional traits of pollinator model species.

Developmental instability in wild Nigerian olive baboons (Papio anubis).

Abstract: Background Developmental instability in archaeological samples can be detected through analysis of skeletal and dental remains. During life, disruptions to biological internal homeostasis that occur during growth and development redirect bodily resources to returning to homeostasis and away from normal processes such as symmetrical development. Because dental enamel does not remodel in life, any deviations from normal development are left behind. Even subtle disturbances to developmental trajectory may be detected in asymmetrical development of traits, specifically a random variation in sides termed fluctuating asymmetry. Human dental fluctuating asymmetry studies are common, but here we investigate the permanent dentition of a non-human primate Papio anubis, for potential fluctuating asymmetry relative to sex, weaning, and reproductive maturity. The sample stems from an outlier population that lives in the wettest and most humid habitat of any studied baboon group. Methods The skulls of adult baboons were collected after their natural death in Gashaka Gumti National Park, Nigeria. The permanent dentition of antimeric teeth (paired) were measured for maximum length and breadth using standard methods. The metrics were analyzed to assess the presence of fluctuating asymmetry in adult permanent mandibular and maxillary dentition. Measurement error and other forms of asymmetry (antisymmetry, directional asymmetry) were considered and dental measures expressing true fluctuating asymmetry were used to address three research questions. Results Males exhibit greater fluctuating asymmetry than females, suggesting that males experience greater overall instability during the developmental period. While weaning is not more stressful than other life history stages for males and females (using the first molar fluctuating asymmetry index as a proxy compared to other teeth), it is more stressful for females than males. The onset of reproduction is also not more stressful than other life history stages for males and females (using the third molar fluctuating asymmetry index as a proxy compared to other teeth), but it is more stressful for males than females. We explore possible explanations for these findings in the discussion.

On the issue of developmental stability of urban tree populations

Abstract: Fluctuating asymmetry as an indirect deviation in the difference between the right and the left bilaterally symmetrical traits is considered an indicative symptom of stress. The results of urban populations studying Betula pendula, Tilia cordata, Quercus robur and Acer platanoides using the conventional normalizing method and the geometric morphometrics are presented. The relationship between the environmental stress of an urbanized area and asymmetry values was analyzed. 8-10% of the samples | R – L | / (R + L) had a normal distribution (K-S test, p 2.5) accompanied by insignificant fluctuating asymmetry in Procrustes ANOVA. The authors emphasize that the toxic effect of pollutants can be associated with the relief and protection from winds in urbanized areas. The heterogeneity of the genotype of plantings from different nurseries increases the factor diversity, which makes the results of the analysis of developmental stability much more critical.