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The social amoeba Dictyostelium discoideum switches between solitary growth and social fruitification depending on nutrient availability. Under starvation, cells aggregate and form fruiting bodies consisting of spores and altruistic stalk cells. Once cells socially committed, they complete fruitification, even if a new source of nutrients becomes available. This social commitment is puzzling because it hinders individual cells from resuming solitary growth quickly. One idea posits that traits that facilitate premature de-commitment are hindered from being selected. We studied outcomes of the premature de-commitment through forced refeeding. Our results show that when refed cells interacted with non-refed cells, some of them became solitary, whereas a fraction was redirected to the altruistic stalk, regardless of their original fate. The refed cells exhibited reduced cohesiveness and were sorted out during morphogenesis. Our findings provide an insight into a division of labor of the social amoeba, in which less cohesive individuals become altruists. [ABSTRACT FROM AUTHOR]

Progress in evolutionary developmental biology (evo‐devo) has deepened our understanding of how intrinsic properties of embryogenesis, along with natural selection and population genetics, shape phenotypic diversity. A focal point of recent empirical and theoretical research is the idea that highly developmentally stable phenotypes are more conserved in evolution. Previously, we demonstrated that in Japanese medaka (Oryzias latipes), embryonic stages and genes with high stability, estimated through whole‐embryo RNA‐seq, are highly conserved in subsequent generations. However, the precise origin of the stability of gene expression levels evaluated at the whole‐embryo level remained unclear. Such stability could be attributed to two distinct sources: stable intracellular expression levels or spatially stable expression patterns. Here we demonstrate that stability observed in whole‐embryo RNA‐seq can be attributed to stability at the cellular level (low variability in gene expression at the cellular levels). We quantified the intercellular variations in expression levels and spatial gene expression patterns for seven key genes involved in patterning dorsoventral and rostrocaudal regions during early development in medaka. We evaluated intracellular variability by counting transcripts and found its significant correlation with variation observed in whole‐embryo RNA‐seq data. Conversely, variation in spatial gene expression patterns, assessed through intraindividual left–right asymmetry, showed no correlation. Given the previously reported correlation between stability and conservation of expression levels throughout embryogenesis, our findings suggest a potential general trend: the stability or instability of developmental systems—and the consequent evolutionary diversity—may be primarily anchored in intrinsic fundamental elements such as the variability of intracellular states. Research highlights: We investigated the precise origins of developmental stability that was previously determined by whole‐embryo RNA‐seq, given its significance in indicating the potential for phenotypic conservation during evolution.Our findings suggest that the developmental stability can be primarily attributed to stability in gene expression at the cellular level, rather than stability in spatial gene expression patterns.The result provides further insight into how embryogenesis introduces bias in phenotypic evolution, and thus paves the way for a deeper understanding of developmental stability that would enable the prediction of phenotypic evolution. [ABSTRACT FROM AUTHOR]

The BBAA subgenomes of hexaploid common wheat can be 'extracted' to constitute a viable and self-reproducing novel tetraploid wheat, termed extracted tetraploid wheat (ETW). Prior studies have shown ETW manifesting phenotypic abnormalities and alteration in gene expression and epigenetic modifications. No population level investigation has been conducted, leaving the issue unclear regarding whether developmental stability, an essential property evolved in all natural organisms, might have been undermined in ETW. Here, we measured variations in five morphological traits and somatic chromosomal stability in populations of ETW and of its hexaploid donor, a resynthesized hexaploid and a natural tetraploid wheat. We observed phenotypic defects in ETW. Meanwhile, we documented much greater within-population variations in ETW than in the other wheat genotypes, most probably due to disrupted developmental stability in ETW. Also, somatic structural chromosome variations were detected only in ETW. Comparative transcriptome analyses indicated that the disrupted developmental stability of ETW is likely linked to massive dysregulation of genome-wide gene expression rather than to genetic mutations. Population network analysis of gene expression implicated intrinsic connectivity among the variable traits, while gene set enrichment analysis provided possible links between dysregulated gene expression and interlaced trait variation. [ABSTRACT FROM AUTHOR]

Management of storage pest insects relies heavily on chemical control, and there is a need to develop more sustainable management practices. Here, we evaluated the impact of 2% ethanol plant extracts of Ajuga reptans L., Ajuga pyramidalis L. (both Lamiaceae), Urtica dioica L. (Urticaceae), and Cannabis sativa L. (Cannabaceae) plants on mortality, population growth, and developmental stability [measuring fluctuating asymmetry (FA)] of the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), a worldwide stored product pest. FA refers to small, random deviations occurring between the left and right sides of bilaterally symmetrical organisms; these deviations increase in response to environmental stress, making FA a reliable method to measure the impact of stress. FA was measured by means of geometric morphometrics, a method that allows for analyzing the whole landmark configuration of the insect, rather than taking single measurements. Extracts of the mentioned plants were used to treat maize (Zea mays L., Poaceae) kernels on which experimental populations of the rice weevil were grown, and we assessed mortality after 24–72 h, population growth after 30–90 days, and developmental stability after 90 days. Screening bioassays showed that S. oryzae adults were most affected by Ajuga extracts; Ajuga spp., especially A. reptans, significantly reduced population growth. In concordance, Ajuga extracts increased FA. The effects of U. dioica and C. sativa extract were less pronounced. None of the extracts significantly affected insect mortality. Overall, it can be concluded that A. reptans and A. pyramidalis are potential sources of bioactive compounds that may be further used for S. oryzae control. The results obtained confirm that variation in body shape asymmetry can be used as an indicator of population disturbance when insects are exposed to different types of stressors. [ABSTRACT FROM AUTHOR]

The temporal variation of the degree of fluctuating asymmetry of the characters of skull morphology, as a measure of the developmental stability, is evaluated in the common shrew (Sorexaraneus L., 1758) in Central Siberia. Four-year cycles in this population under conditions of climatic stability in the past century were accompanied by significant changes in the level of developmental stability, suggesting a negative impact under a high density. Population fluctuations under the conditions of climatic instability in this century commonly occur without essential changes in the developmental stability, which can be related to both the impact of oscillations in the environmental conditions and an increase in the carrying capacity of the habitat due to the increase in temperature. Deterioration of developmental stability takes place occasionally in the case of an adverse overpopulation impact in the year of peak population abundance that is beyond the certain threshold level, which has increased due to climate change. The results indicate the importance of simultaneous monitoring of population abundance and developmental stability to provide information on possible mechanisms of changes in the population dynamics that occur due to climate change. [ABSTRACT FROM AUTHOR]

Under temperature sex determination (TSD), sex is determined by temperature during embryonic development. Depending on ecological and physiological traits and plasticity, TSD species may face demographic collapse due to climate change. In this context, asymmetry in bilateral organisms can be used as a proxy for developmental instability and, therefore, deviations from optimal incubation conditions. Using Tarentola mauritanica gecko as a model, this study aimed first to confirm TSD, its pattern and pivotal temperature, and second to assess the local adaptation of TSD and variation of asymmetry patterns across four populations under different thermal regimes. Eggs were incubated at different temperatures, and hatchlings were sexed and measured. The number of lamellae was counted in adults and hatchlings. Results were compatible with a TSD pattern with males generated at low and females at high incubation temperatures. Estimated pivotal temperature coincided with the temperature producing lower embryonic mortality, evidencing selection towards balanced sex ratios. The temperature of oviposition was conservatively selected by gravid females. Asymmetry patterns found were likely related to nest temperature fluctuations. Overall, the rigidity of TSD may compromise reproductive success, and demographic stability in this species in case thermal nest choice becomes constrained by climate change. [ABSTRACT FROM AUTHOR]

Objectives: The level of fluctuating asymmetry is suggested as a putative signal of developmental stability, thus according to this theoretical framework more symmetric individuals should be in better biological condition and have greater reproductive potential. Here we hypothesize that women with more symmetric faces have more successful reproduction. Methods: Data were collected from 164 postmenopausal Polish women. Facial photographs were taken and the overall facial asymmetry (OFA) was calculated. The associations between the OFA and reproductive parameters were analyzed using multiple regression models. Furthermore, the mediation analysis was conducted to test for the indirect effects of the OFA on reproductive success. Results: There was a statistically significant relationship between the OFA and the number of children born, which was mediated by the age at first reproduction (p = 0.03), however, the size of the effect was rather low. Women with more symmetric faces had an earlier age at first reproduction and, in consequence, a greater number of children. Discussion: As fluctuating asymmetry is suggested to be established in utero, these findings shed light on the possible life‐long importance of developmental conditions in shaping women's reproductive potential and performance. [ABSTRACT FROM AUTHOR]

Simple Summary: Size and shape are important features of most living beings, and the capacity of the organism to regulate size and shape during growth, containing the effects of developmental disturbances of different origins, is considered a key adaptation. Through a morphological study on the larvae of the cabbage butterfly Pieris brassicae, reared in conditions close to the natural environment, we found that the regulatory mechanisms for limiting the effects of developmental disturbances, known to be effective under strictly controlled, very stable laboratory conditions, are also effective during growth under more natural environmental conditions. This study may contribute to better characterization of these regulatory mechanisms and their combined effects in the developmental interactions between the organism and its environment. Size and shape are important determinants of fitness in most living beings. Accordingly, the capacity of the organism to regulate size and shape during growth, containing the effects of developmental disturbances of different origin, is considered a key feature of the developmental system. In a recent study, through a geometric morphometric analysis on a laboratory-reared sample of the lepidopteran Pieris brassicae, we found evidence of regulatory mechanisms able to restrain size and shape variation, including bilateral fluctuating asymmetry, during larval development. However, the efficacy of the regulatory mechanism under greater environmental variation remains to be explored. Here, based on a field-reared sample of the same species, by adopting identical measurements of size and shape variation, we found that the regulatory mechanisms for containing the effects of developmental disturbances during larval growth in P. brassicae are also effective under more natural environmental conditions. This study may contribute to better characterization of the mechanisms of developmental stability and canalization and their combined effects in the developmental interactions between the organism and its environment. [ABSTRACT FROM AUTHOR]

Developmental noise is a variety that is not related to the usually distinguished sources of phenotypic diversity, i.e., differences in the genotype and in the environment. This variation arises in the process of the realization of genetic information and reflects the imperfection of ontogenetic processes. The most common measure of it is the value of fluctuating asymmetry as slight deviations from the symmetry. Developmental noise proves to be one of the main sources of intrapopulation phenotypic diversity. The magnitude of this variability is an ontogenetic response to environmental or genetic stress, and its assessment, in fact, provides a unique opportunity to estimate the developing system condition. The level of developmental noise, characterizing an organism's condition, acts as another population parameter that allows to approach the evaluation of the community condition. Initial deviations in the system condition can be detected even against the background of optimal estimates of abundance, biodiversity, and ecosystem functioning. [ABSTRACT FROM AUTHOR]

Evolution of unicellular to multicellular organisms must resolve conflicts in reproductive interests between individual cells and the group. The social amoeba Dictyostelium discoideum is a soil-living eukaryote with facultative sociality. While cells grow in the presence of nutrients, cells aggregate under starvation to form fruiting bodies containing spores and altruistic stalk cells. Once cells socially committed, they complete formation of fruiting bodies, even if a new source of nutrients becomes available. The persistence of this social commitment raises questions as it inhibits individual cells from swiftly returning to solitary growth. I hypothesize that traits enabling premature de-commitment are hindered from being selected. Recent work has revealed outcomes of the premature de-commitment through forced refeeding; The de-committed cells take an altruistic prestalk-like position due to their reduced cohesiveness through interactions with socially committed cells. I constructed an evolutionary model assuming their division of labor. The results revealed a valley in the fitness landscape that prevented invasion of de-committing mutants, indicating evolutionary stability of the social commitment. The findings provide a general scheme that maintains multicellularity by evolving a specific division of labor, in which less cohesive individuals become altruists. • Dictyostelium stays multicellular, even with environmental changes. • The social commitment inhibits solitary cell growth, a longstanding question. • Division of labor reduces payoff from quitting cooperation, punishing de-commitment. • De-committed mutants can't invade, indicating social commitment's maintenance. [ABSTRACT FROM AUTHOR]

Premise of research. Cotyledons have important functions in the early seedling stage and have important effects on later stages, but we know little about the relationships among developmental stability, canalization, and phenotypic plasticity in cotyledons. Methodology. We conducted a field experiment with five herbaceous species, subjecting them to contrasting light conditions and burial depths and measuring their cotyledon size and fluctuating asymmetry (random deviation from perfect bilateral symmetry, indicating developmental stability or instability), coefficient of variation, and plasticity of cotyledon size, to investigate the relationships among cotyledon developmental stability, canalization, and plasticity in response to shading and deep burial. Pivotal results. Pharbitis purpurea , Convolvulus arvensis , and Carpesium abrotanoides had increased cotyledon size in response to shading at both burial depths, and Abutilon theophrasti showed reduced cotyledon size in response to shading versus full light at shallow depth but greater cotyledon size in response to both shading and deep burial. Shading increased cotyledon fluctuating asymmetry of P. purpurea and C. abrotanoides , while deep burial decreased it. Cotyledon fluctuating asymmetry had positive correlations with coefficient of variation and plasticity in response to shading, with little correlation between coefficient of variation and plasticity. Conclusions. Results suggested that A. theophrasti may have greater tolerance for multiple stresses than the other species, and deep burial may improve shade tolerance of cotyledons through moderate levels of stress selection. Both developmental instability and decreased canalization may indicate the state of faster growth. Developmental instability can facilitate more active response to shading in cotyledons, while the relationship between canalization and plasticity should be more complex. [ABSTRACT FROM AUTHOR]

Background: Despite the morphological diversity of animals, their basic anatomical patterns—the body plans in each animal phylum—have remained highly conserved over hundreds of millions of evolutionary years. This is attributed to conservation of the body plan-establishing developmental period (the phylotypic period) in each lineage. However, the evolutionary mechanism behind this phylotypic period conservation remains under debate. A variety of hypotheses based on the concept of modern synthesis have been proposed, such as negative selection in the phylotypic period through its vulnerability to embryonic lethality. Here we tested a new hypothesis that the phylotypic period is developmentally stable; it has less potential to produce phenotypic variations than the other stages, and this has most likely led to the evolutionary conservation of body plans. Results: By analyzing the embryos of inbred Japanese medaka embryos raised under the same laboratory conditions and measuring the whole embryonic transcriptome as a phenotype, we found that the phylotypic period has greater developmental stability than other stages. Comparison of phenotypic differences between two wild medaka populations indicated that the phylotypic period and its genes in this period remained less variational, even after environmental and mutational modifications accumulated during intraspecies evolution. Genes with stable expression levels were enriched with those involved in cell-cell signalling and morphological specification such as Wnt and Hox, implying possible involvement in body plan development of these genes. Conclusions: This study demonstrated the correspondence between the developmental stage with low potential to produce phenotypic variations and that with low diversity in micro- and macroevolution, namely the phylotypic period. Whereas modern synthesis explains evolution as a process of shaping of phenotypic variations caused by mutations, our results highlight the possibility that phenotypic variations are readily limited by the intrinsic nature of organisms, namely developmental stability, thus biasing evolutionary outcomes. [ABSTRACT FROM AUTHOR]

Understanding how environmental variation influences even cryptic traits is important to clarify the roles of selection and developmental constraints in past evolutionary divergence and to predict future adaptation under environmental change. Female yellow dung flies (Scathophaga stercoraria) typically have three sperm storage compartments (3S), but occasionally four (4S). More spermathecae are thought to be a female adaptation facilitating sperm sorting after mating, but the phenotype is very rare in nature. We manipulated the flies' developmental environment by food restriction, pesticides, and hot temperatures to investigate the nature and extent of developmental plasticity of this trait, and whether spermatheca expression correlates with measures of performance and developmental stability, as would be expected if 4S expression is a developmental aberration. The spermathecal polymorphism of yellow dung fly females is heritable, but also highly developmentally plastic, varying strongly with rearing conditions. 4S expression is tightly linked to growth rate, and weakly positively correlated with fluctuating asymmetry of wings and legs, suggesting that the production of a fourth spermatheca could be a nonadaptive developmental aberration. However, spermathecal plasticity is opposite in the closely related and ecologically similar Scathophaga suilla, demonstrating that overexpression of spermathecae under developmental stress is not universal. At the same time, we found overall mortality costs as well as benefits of 4S pheno‐ and genotypes (also affecting male siblings), suggesting that a life history trade‐off may potentially moderate 4S expression. We conclude that the release of cryptic genetic variation in spermatheca number in the face of strong environmental variation may expose hidden traits (here reproductive morphology) to natural selection (here under climate warming or food augmentation). Once exposed, hidden traits can potentially undergo rapid genetic assimilation, even in cases when trait changes are first triggered by random errors that destabilize developmental processes. Highlights: Female yellow dung flies naturally vary in number of sperm storage compartments (3S or 4S).This spermathecal polymorphism is strongly heritable but also developmentally plastic.4S expression is linked to growth rate and weakly correlated with fluctuating asymmetry, so potentially a developmental aberration.There are mortality costs as well as benefits for 4S phenotypes, suggesting adaptive life‐history trade‐offs.Spermathecal plasticity differs in the closely related and ecologically similar Scathophaga suilla.Environmental changes can expose hidden traits with initially no function to natural selection. [ABSTRACT FROM AUTHOR]

Hybridization is a source of phenotypic novelty and variation because of increased additive genetic variation. Yet, the roles of nonadditive allelic interactions in shaping phenotypic mean and variance of hybrids have been underappreciated. Here, we examine the distributions of male‐mating traits in F1 hybrids via a meta‐analysis of 3208 effect sizes from 39 animal species pairs. Although additivity sets phenotypic distributions of F1s to be intermediate, F1s also showed recessivity and resemblance to maternal species. F1s expressed novel phenotypes (beyond the range of both parents) in 65% of species pairs, often associated with increased phenotypic variability. Overall, however, F1s expressed smaller variation than parents in 51% of traits. Although genetic divergence between parents did not impact phenotypic novelty, it increased phenotypic variability of F1s. By creating novel phenotypes with increased variability, nonadditivity of heterozygotic genome may play key roles in determining mating success of F1s, and their subsequent extinction or speciation. [ABSTRACT FROM AUTHOR]

Pathways through which phenotypic variation among individuals arise can be complex. One assumption often made in relation to intraspecific diversity is that the stability or predictability of the environment will interact with expression of the underlying phenotypic variation. To address biological complexity below the species level, we investigated variability across years in morphology and annual growth increments between and within two sympatric lake charr Salvelinus namaycush ecotypes in Rush Lake, USA. A rapid phenotypic shift in body and head shape was found within a decade. The magnitude and direction of the observed phenotypic change were consistent in both ecotypes, which suggests similar pathways caused the variation over time. Over the same time period, annual growth increments declined for both lake charr ecotypes and corresponded with a consistent phenotypic shift of each ecotype. Despite ecotype‐specific annual growth changes in response to winter conditions, the observed annual growth shift for both ecotypes was linked, to some degree, with variation in the environment. Particularly, a declining trend in regional cloud cover was associated with an increase of early‐stage (ages 1–3) annual growth for lake charr of Rush Lake. Underlying mechanisms causing changes in growth rates and constrained morphological modulation are not fully understood. An improved knowledge of the biology hidden within the expression of phenotypic variation promises to clarify our understanding of temporal morphological diversity and instability. [ABSTRACT FROM AUTHOR]

The Hippo signaling pathway is a major regulator of organ growth, which controls the activity of the transcription coactivator Yorkie (Yki) in Drosophila and its homolog YAP in mammals. Both Yki and YAP proteins exist as alternatively spliced isoforms containing either one or two WW domains. The biological importance of this conserved alternative splicing event is unknown. Here, we identify the splicing factor B52 as a regulator of yki alternative splicing in Drosophila and show that B52 modulates growth in part through modulation of yki alternative splicing. Yki isoforms differ by their transcriptional activity as well as their ability to bind and bridge PPxY motifs‐containing partners, and can compete in vivo. Strikingly, flies in which yki alternative splicing has been abrogated, thus expressing only Yki2 isoform, exhibit fluctuating wing asymmetry, a signal of developmental instability. Our results identify yki alternative splicing as a new level of modulation of the Hippo pathway, that is required for growth equilibration during development. This study provides the first demonstration that the process of alternative splicing contributes to developmental robustness. SYNOPSIS: The Hippo pathway effector Yorkie (Yki) and its mammalian homolog YAP exist in splicing isoforms containing one or two WW domains. This study shows that the splicing factor B52 is necessary for inclusion of an alternative yki exon in Drosophila, and that yki alternative splicing is required for developmental robustness. B52 depletion favors skipping of yki alternative exon, reduces Yki activity and tissue growthAbsence of one of the WW domains weakens Yki interactions with PPxY‐containing proteins and decreases its transcriptional activityYki isoforms can compete with each other for transcription factor binding in vivoFlies engineered to express only the full‐length Yki2 isoform exhibit fluctuating wing asymmetry [ABSTRACT FROM AUTHOR]

By adopting a longitudinal study design and through geometric morphometrics methods, we investigated size and shape regulation in the head capsule during the larval development of the cabbage butterfly Pieris brassicae under laboratory conditions. We found evidence of size regulation by compensatory growth, although not equally effective in all larval stages. Size compensation is not attained through the regulation of developmental timing, but rather through the modulation of per‐time growth rate. As for the shape, neither the variance of the symmetric component of shape, nor the level of fluctuating asymmetry show any evidence of increase across stages, either at the population or individual level, which is interpreted as a mark of ontogenetic shape regulation. In addition, also the geometry of individual asymmetry is basically conserved across stages. While providing specific documentation on the ontogeny of size and shape variation in this insect, this study may contribute to a more general understanding of developmental regulation and its influence on phenotypic evolution. Research Highlights: We investigated the ontogenetic progression of size and shape variation (including fluctuating asymmetry) in the butterfly Pieris brassicae with a longitudinal study‐design. Larval development of this insect shows the mark of several forms of developmental regulation, both in size and shape, which exhibit a certain degree of independence from each other. [ABSTRACT FROM AUTHOR]

Epigenetic processes manage gene expression and products in a real‐time manner, allowing a single genome to display different phenotypes. In this paper, we discussed the relevance of assessing the different sources of epigenetic variation in natural populations. For a given genotype, the epigenetic variation could be environmentally induced or occur randomly. Strategies developed by organisms to face environmental fluctuations such as phenotypic plasticity and diversified bet‐hedging rely, respectively, on these different sources. Random variation can also represent a proxy of developmental stability and can be used to assess how organisms deal with stressful environmental conditions. We then proposed the microbiome as an extension of the epigenotype of the host to assess the factors determining the establishment of the community of microorganisms. Finally, we discussed these perspectives in the applied context of conservation. [ABSTRACT FROM AUTHOR]

Animal personality can be defined as conspecific individuals consistently differing in behavioral tendencies. Personality is typically identified by behavioral repeatability, which occurs when within‐individual variance is low relative to among‐individual variance in the population. Intraspecific comparisons of behavioral repeatability in juveniles and adults within and across years are rare, but would be useful for testing hypotheses related to origins of animal personality and whether individuals exhibit stable or diverging behavior with ontogeny. To examine within‐ and across‐year behavioral repeatability for eastern box turtles (Terrapene carolina), we assessed boldness (movement latency after brief confinement) of captive‐born juveniles twice within three days when eight months old. We then repeated these tests for the same individuals one year later. Juveniles exhibited repeatable boldness within and across years. Although increasing body temperature was slightly associated with decreased movement latency, test year (1 or 2), or housing experience (being raised in an enriched or unenriched condition) had no effects on boldness. We also assessed across‐year repeatability of boldness (head emergence from the shell after brief confinement) for wild adults at 1–3 year intervals. Adults also exhibited repeatable across‐year boldness that was of similar magnitude to juveniles. We found no indication that sex class or whether adults had been radio‐tracked influenced boldness. Our results suggest eastern box turtles demonstrate consistent individuality in boldness from an early age that is largely unaffected by temporal or environmental variation, and these behavioral differences can be maintained for multiple years in captivity and the wild, contrasting with theoretical expectations for personality development. These findings add to recent accumulating evidence demonstrating juvenile and adult box turtles exhibit multiple repeatable behaviors over the short‐ and long‐term. We suggest this species is quickly gaining traction as a model organism for studying the proximate and ultimate causes of personality development within long‐lived animals. [ABSTRACT FROM AUTHOR]

• Expansion of urban areas is one of the greatest threats to reptiles. • These findings are contradictory and based solely on lizard species. • Fluctuating asymmetry is used to express developmental instability. • Urban land use has a negative effect on development stability of dice snakes. • Human-modified habitats lead to poorer body condition of dice snakes. The expansion of urban areas leads to a decrease in natural habitats, resulting some species to live in urban environments. Novel environmental factors might influence their size, body condition and development stability. The environmentally induced developmental instability can be indicated by fluctuating symmetry, which means random deviations from perfect symmetry in bilaterally symmetric creatures. Our research aimed to explore the impact of various urbanization factors on snake populations within urban habitats. To achieve this, we examined how dice snake (Natrix tessellata) populations differ in their asymmetry, body condition and size in a lake characterized by highly modified lakeside habitats, intensive urban land use, and severe human disturbance. The average size, body condition and two asymmetry indices were determined for 25 dice snake populations around Lake Balaton in Hungary. The impacts of the urban environment were characterized by land use and local variables, and the risk of road kill was also estimated. Populations living in areas with a more intensive road network or near a main road showed more asymmetric traits. It is conceivable that pollutants from vehicle traffic lead to developmental disorders that manifest themselves in more asymmetric individuals. In addition, the body condition of snakes was negatively correlated with the area of the harbours, possibly due to the intensive boat traffic and human disturbance. Finally, populations living in more urbanized areas had larger body sizes meaning that despite its negative effects through pollution, anthropized areas can provide a suitable habitat for dice snakes. While urban artificial surroundings can function as suitable habitats, our results confirm that urban environmental factors have negative effects on dice snakes. Our findings indicate that the density of road networks and the proximity of roads have adverse effects on the developmental stability of urban snakes. This underscores the need to implement conservation actions to mitigate the negative effects of roads on biodiversity. [ABSTRACT FROM AUTHOR]

Parental mind-mindedness, the parent's propensity to treat the child as an intentional agent, has repeatedly shown to promote children's development of social understanding and secure attachment. Less is known about whether the impact of maternal and paternal mind-mindedness extends to children's social and behavior problems. We investigated the combined effect of mothers' and fathers' (N = 104) mind-mindedness at 4, 12, and 30 months on children's social competence and externalizing and internalizing behavior problems at 4.5 years. Besides, we examined the stability, continuity, parental concordance, and inter-parental differences in the use of mind-related comments. Appropriate mind-mindedness (i.e., correct interpretations of the child's mental states) and nonattuned mind-mindedness (i.e., misinterpretations of the child's mental states) were observed during parent-child free-play interactions. Social competence, internalizing and externalizing behavior problems were assessed using both parents' reports. Hierarchical multiple regression analyses showed that, at 12 months, infrequent use of appropriate mind-related comments of both parents predicted children's externalizing problems, while their frequent use of nonattuned comments predicted children's low social competence. Furthermore, mothers' frequent use of nonattuned comments at 12 and 30 months and fathers' nonattuned comments at 30 months predicted children's externalizing behavior. The findings suggest that both parents' low use of mind-related comments, and frequent misinterpretations of their child's mind, may act as risk factors for later social and behavior problems of their child. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyse the relationship between childhood socioeconomic conditions and body asymmetry in young Polish women. The study measured fluctuating asymmetry (FA), which refers to small random deviations from perfect symmetry in bilaterally paired body structures. Data were obtained from 620 female students aged from 19 to 25 years recruited from Jagiellonian University in Cracow, Poland. The research was carried out in the period from January 2016 to May 2017. A composite fluctuating asymmetry (cFA) of the women was calculated using five bilateral body traits. The lengths and widths of the women's ears, lengths of their 2nd and 4th digits and wrist widths of the right and left sides of the body were measured twice using standard methodology. The following data were collected in a questionnaire: degree of urbanization of the woman's place of residence during childhood, number of older siblings, parental education and woman's dominant hand. The results showed a tendency for FA to fall with an increase in parental education, and to rise with an increase in number of older siblings. The level of FA was significantly lower in women from rural areas than in those from cities. The results of the study show that FA in early adulthood is significantly associated with socioeconomic status during childhood, and confirm that the level of FA in adulthood may be a good indicator of stress factors in the early stages of development. [ABSTRACT FROM AUTHOR]

Parthenogenetic species are usually considered to be short‐lived due to the accumulation of adverse mutations, lack of genetic variability, and inability to adapt to changing environment. If so, one may expect that the phenotype of clonal organisms may reflect such genetic and/or environmental stress. To test this hypothesis, we compared the developmental stability of bisexual and parthenogenetic lizards of the genus Darevskia. We assessed asymmetries in three meristic traits: ventral, preanal, and supratemporal scales. Our results suggest that the amount of ventral and preanal asymmetries is significantly higher in clones compared with their maternal, but not paternal, progenitor species. However, it is questionable, whether this is a consequence of clonality, as it may be considered a mild form of outbreeding depression as well. Moreover, most ventral asymmetries were found in the bisexual species Darevskia valentini. We suggest that greater differences in asymmetry levels among bisexuals may be, for instance, a consequence of the population size: the smaller the population, the higher the inbreeding and the developmental instability. On the basis of the traits examined in this study, the parthenogens do not seem to be of significantly poorer quality. [ABSTRACT FROM AUTHOR]

Developmental instability provides a powerful monitoring tool to detect threats prior to population declines. Consequently, assessing the level of developmental instability by measuring fluctuating asymmetry (FA) of bilaterally symmetrical traits in association with environmental stress has become increasingly attractive. However, many studies failed in detecting a clear connection of FA to environmental stressors. Some of these may have suffered from large measurement error (ME) or the use of inappropriate methods. Here, we compared measurement accuracy and FA outcome from manual calliper measurements with those from non-destructive micro-3D-computed tomography (µCT) based skeletal measurements. Amphibians are assumed to be ideal models for measuring fluctuating asymmetry due to their sensitivity to environmental stress. For our study, we chose two bilateral, metric traits (femur and radio--ulna length) of the European Common Frog, Rana temporaria. Calliper measurements revealed meaningful FA estimates (i.e., FA exceeded ME) for radio-- ulna length only. In contrast, µCT-based measurements delivered meaningful FA estimates for both traits. ME was about twice as high for calliper measurements compared to µCT-based measurements, resulting in inflated levels of FA. Using callipers, we observed higher ME for femur measurements than for radio--ulna, meaning that ME strongly depended on the respective trait. When using µCT, however, we observed comparable ME between both traits. Our study revealed that analyses of developmental instability using manual measurements should be treated with caution. For smaller vertebrates we recommend skeletal measurements with µCT as a valuable alternative due to its greater reliability, thereby allowing for multi-trait analyses with equal accuracy. [ABSTRACT FROM AUTHOR]

The behavioral competence of captive‐bred individuals – an important source population for translocation programs – may differ from that of wild‐born individuals and these differences may influence post‐release survival. Some behaviors will be more robust, or developmentally stable, than others in the face of the environmental novelties of captivity. Here, we investigated developmental stability of foraging behavior by quantifying bamboo feeding behavior in captive‐bred and wild‐born giant pandas, Ailuropoda melanleuca. As an energy‐limited species adapted to a low‐nutrition diet, any reductions in feeding efficiency may compromise post‐release survival. Using video of 22 captive pandas, we measured several components of the panda's elaborate bamboo feeding behavior repertoire. We found that captive‐born and wild‐born pandas displayed the same repertoire of feeding behaviors, suggesting developmental stability in these motor patterns, but that they employed them differently with different parts of the bamboo. Captive‐born pandas devoted less time and effort to handling and chewing leaves while allocating more effort to the consumption of large culms than did wild‐born pandas. Captive‐born pandas also handled small culm and stripped small culms to prepare them for consumption less often than did wild‐born pandas. All of these behavioral differences indicate that wild‐born pandas in captivity behave in a manner more similar to wild pandas, and focus their behavioral effort on more nutritious bamboo. Thus, these aspects of captive‐born panda feeding behavior may be compromised, and were not developmentally stable in the captive environment. These behavioral differences are cause for concern and should be the subject of future study to determine whether they forecast compromised fitness in translocations. Evaluating developmental stability and behavioral competence should be a key component of captive‐release translocation programs, serving to guide pre‐release training and selection of individuals to be released. The behavioral competence of captive‐bred individuals may differ from that of wild‐born individuals and these differences may influence post‐release survival in translocation programs. We investigated developmental stability of foraging behavior by quantifying bamboo‐feeding behavior in captive‐bred and wild‐born giant pandas. Wild‐born pandas in captivity behaved in a manner more similar to wild pandas, and focused their behavioral effort on more nutritious bamboo, indicating that captive‐born panda feeding behavior may be compromised and that feeding behavior is influenced by development in a captive environment. [ABSTRACT FROM AUTHOR]

Fluctuating asymmetry (FA), which is defined as the magnitude of the random deviations from a symmetrical shape, reflects developmental instability and is commonly assumed to increase under environmental and genetic stress. We monitored the leaf FA of mountain birch, Betula pubescens subsp. czerepanovii , from 1993 to 2017 in individually marked trees at 21 sites around the copper‑nickel smelter at Monchegorsk, and we then analysed the results with respect to spatial and temporal variation in pollution, climate and background insect herbivory. Responses of leaf FA to different stressors were stressor specific: FA did not correlate with pollution load, it decreased significantly with an increase in June air temperature and it increased slightly but significantly with an increase in the previous-year leaf damage due to defoliating and leafmining insects. Our findings suggest that climate warming is unlikely to impose stress on the explored mountain birch populations, but even small increases in insect herbivory may adversely affect birch trees. However, these conclusions, since they are based on an observational study, should be viewed as tentative until confirmed by controlled experiments. We also demonstrated that the use of non-blinded measurements, which are prone to confirmation bias, was the primary reason for the earlier report of an increase in birch leaf FA near the Monchegorsk smelter. We hope that our findings will promote a wide use of blinded methods in ecological research and that they will contribute to debunking the myth that plant leaf FA consistently increases with increases in environmental pollution. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: More symmetric organisms are perceived as more attractive. Fluctuating asymmetry (FA) i.e. small, random deviations from perfect bilateral symmetry, is supposed to inform about developmental instability. According to the good genes hypothesis, a low level of FA is a putative cue to an organism's biological quality. An important aspect of this quality is the immune system functioning. The aim of this study was to evaluate the relationship between immune system functioning and body symmetry in healthy people. Materials and Methods: The composite body FA (cFA) was assessed on the basis of six bilateral traits (on hands and feet). The ISF was determined by many innate (total complement and lysozyme activity, neutrophils function) and adaptive immune parameters (T CD3 and B CD19 lymphocytes, total IgA and IgG and response to flu vaccine). A total of 98 men and 92 women were subjected to flu (among them 37 men and 30 women also to tetanus) vaccination. The blood samples were collected before and 4 weeks after the antigens exposure. Immunomodulatory factors: participant's age, body fat, and free testosterone level, were controlled. Results: Apart from the weak positive association between CD3 or CD19 and cFA in men, we found no association between the level of body symmetry and the rest of the analyzed immune parameters for both sexes. Discussion: Our results are the opposite of the good genes hypothesis prediction and suggest that in western, healthy populations, human mate preferences for more symmetric bodies are not related to immune competence. [ABSTRACT FROM AUTHOR]

Drosophila suzukii (Matsumura, 1931) is a highly successful invasive dipteran which represents a serious threat for global fruit industry. Among other adaptive traits, D. suzukii owes its success to the derived morphological features of its ovipositor, which allows the insect to exploit the exclusive ecological niche of fresh fruit, thus avoiding competition with other closely related species. With the aim of investigating temperature-induced phenotypic plasticity of D. suzukii ovipositor, we reared this insect in four different laboratory conditions, represented by the combination of two developmental temperatures and two diet regimes for the larvae. We recorded the effects of these two factors on ovipositor size and shape and overall body size through a combination of distance-based and geometric morphometric analyses. Results showed that insects attain the largest body sizes at lower temperature, whereas the diet does not determine significant difference in size. However, the effect on size of the two factors is less pronounced in the ovipositor, which shows a negative allometry with respect to body size in all treatments. At higher temperature, ovipositor shape tends also to co-vary with its own size. Neither temperature nor diet have significant effect on ovipositor bilateral fluctuating asymmetry. These results confirm the hypothesis that in D. suzukii the toughened valve of the ovipositor are subjected to effective morpho-functional constraints, while probably being under strong selection by reason of their mechanical role. [ABSTRACT FROM AUTHOR]

Abstract: The evolution of phenotypic plasticity of plant traits may be constrained by costs and limits. However, the precise constraints are still unclear for many traits under different ecological contexts. In a glasshouse experiment, we grew ramets of 12 genotypes of a clonal plant Hydrocotyle vulgaris under the control (full light and no flood), shade and flood conditions and tested the potential costs and limits of plasticity in 13 morphological and physiological traits in response to light availability and flood variation. In particular, we used multiple regression and correlation analyses to evaluate potential plasticity costs, developmental instability costs and developmental range limits of each trait. We detected significant costs of plasticity in specific petiole length and specific leaf area in response to shade under the full light condition and developmental range limits in specific internode length and intercellular CO2 concentration in response to light availability variation. However, we did not observe significant costs or limits of plasticity in any of the 13 traits in response to flood variation. Our results suggest that the evolution of phenotypic plasticity in plant traits can be constrained by costs and limits, but such constraints may be infrequent and differ under different environmental contexts. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: Fluctuating asymmetry (FA) is hypothesized to reflect the level of an individual's developmental instability, and therefore genetic quality. As a potential signal of biological condition, female body (including breast) symmetry was shown to be perceived as more attractive in mate choice context. If symmetry reflects a woman's genetic quality, it is possible that FA, similarly to other maternal anthropometric cues of biological condition (e.g., body height or waist‐to‐hip ratio), may be also related to her offspring condition. Materials and Methods: To test this, breast and body asymmetry was measured in 93 pregnant women in the 1st, 2nd, and 3rd pregnancy trimester. Child's birth weight, length, chest and head circumference, information on the Apgar score, congenital malformations, and birth complications was taken from hospital records. The relationships between offspring birth characteristics and maternal breast FA and body FA were analyzed separately, controlled for a child's sex and maternal weight in pregnancy. Results: Breast asymmetry was not a predictor of a child's neonatal condition assessed from morphological parameters at birth. Asymmetry of maternal non‐ornamental body characteristcs, commonly used to assess body FA, correlated negatively with a child's weight, head and chest circumference at birth. Discussion: A composite asymmetry index of eight body traits, non‐sexually selected characteristics, seems to be a better predictor of a woman's ability to invest in fetus during pregnancy than breast asymmetry, sexual ornamentation that is perceived as a signal of a woman's attractiveness and biological condition. [ABSTRACT FROM AUTHOR]

Beekeeping with the western honey bee ( Apis mellifera ) is important in tropical regions but scant information is available on the possible consequences of global warming for tropical beekeeping. We evaluated the effect of heat stress on developmental stability, the age at onset of foraging (AOF) and longevity in Africanized honey bees (AHBs) in the Yucatan Peninsula of Mexico, one of the main honey producing areas in the Neotropics, where high temperatures occur in spring and summer. To do so, we reared worker AHB pupae under a fluctuating temperature regime, simulating current tropical heatwaves, with a high temperature peak of 40.0 °C for 1 h daily across six days, and compared them to control pupae reared at stable temperatures of 34.0–35.5 °C. Heat stress did not markedly affect overall body size, though the forewing of heat-stressed bees was slightly shorter than controls. However, bees reared under heat stress showed significantly greater fluctuating asymmetry (FA) in forewing shape. Heat stress also decreased AOF and reduced longevity. Our results show that changes occur in the phenotype and behavior of honey bees under heat stress, with potential consequences for colony fitness. [ABSTRACT FROM AUTHOR]

Light is an important factor of the plant's environment. The aim of research was to confirm the hypothesis on the influence of different irradiation levels on the fluctuating asymmetry (FA) value of bilateral traits of plants cultivated in the indoor plant lighting. The object of research was the plants of cucumber (Cucumis sativus L) as one of the main glasshouse crops. Young 14-day-old cucumber plants in the first true leaf phase were studied. Different irradiation levels (15.0, 22.5 and 30 W m-2) were maintained by fluorescent lamps. An essential asymmetry of bilateral structures in plants grown under different irradiation levels was observed. It was found that statistically significant lower values of FA, that is greater stability of plant development, correspond to increased plant performance. When the irradiation level was switched from 15 to 30 W m-2 (by 100%), the FA index for different bilateral structures varied by different amount: in terms of cotyledons mass it decreased from 0.046 to 0.032 relative units (by 30.2%), in terms of chlorophyll content in cotyledons it increased from 0.038 to 0.073 relative units (by 88.6%). In some bilateral structures the FA index variation was rather small: in terms of the cotyledon area it was zero, in terms of the cotyledon thickness - by 1.8%. It was experimentally prove through the example of cucumber plants that FA index could be used as an indicator of plant developmental stability, characterizing the deviations of the growing environment parameters from the normal state in the indoor cultivating. [ABSTRACT FROM AUTHOR]

The relationship between the general factor of intelligence ( g ) and handedness is investigated using a combined sample of 23511 respondents from three large databases: the NLSY’79 (US), NLSY’97 (US) and NCDS (UK). Dextrals – those who use their right hands were found to be 1.22 IQ points higher than sinistrals (left handers) after controlling for sex and age and correcting for sources of measurement error. To see if the association between IQ and handedness was strongest on the abilities that were the best measures of g, the method of correlated vectors was used to test for moderation. Across the three studies, g was found to very weakly negatively moderate the association between ability measure and handedness ( ρ  = −.023, K  = 3, N  = 23511), however in the NLSY’79, the coding speed subtest was an outlier in terms of the strength of its association with handedness. Its removal yielded indications of positive moderation in this dataset, which when aggregated boosted the overall vector correlation value to .539 ( K  = 3, N  = 23511), suggesting that g might be an important moderator of this relationship. Secondary analysis of secular trend data on the changing percentage of sinistrals in Western populations indicates that overall, sinistrality has increased, entailing a g decline of .106 points over 150 years (.006 points per decade). The secular increase in sinistrality is consistent with other data indicating long-term declines in developmental stability and may stem from some combination of increasing mutation load and environmental stress in Western populations. [ABSTRACT FROM AUTHOR]

The value of fluctuating asymmetry (FA) of trees and small mammals is considered as an indicator of developmental instability. The urban territories with recreation zones, sites with increased radiation background, and the areas affected by mining facilities have been analyzed as anthropogenically transformed areas. The following tree and small mammalian species are the objects of the study: Siberian silver birch ( Betula platyphylla), spreading birch ( B. divaricata), dwarf birch ( B. exilis), shrub alder ( Duschekia fruticosa), basket willow ( Salix viminalis), northern red-backed vole ( Clethrionomys rutilus), tundra vole ( Microtus oeconomus), Laxmann's shrew ( Sorex caecutiens), and tundra shrew ( S. tundrensis). In total, 60000 leaves have been measured and 3500 rodent sculls have been examined. The issues of selection of bioindicator species and the factors distorting the results of environmental quality assessment according to developmental instability are discussed. A statistically significant increase in FA of plants is recorded in urban territories as compared with the wildlife biotopes. A positive correlation of FA value with transport load, concentration of heavy metals in soil, and atmospheric air pollution is observed. The proximity to a roadway and the state of road pavement influence the FA value. The main source of pollution in the administrative center (Yakutsk) is motor vehicles; correspondingly, large streets and crossroads with a high transport load are the most polluted sites. As for the industrial center (city of Mirnyi), pollution spreads from the areas affected by mining to the residential area. The main pollution source in a small administrative center (city of Aldan) is the federal highway. It is recommended to concurrently use the FA characteristics of plant and animals in the area affected by the mining industry. Characteristic of this industry is withdrawal of large areas of natural landscapes; typically, transformed plots alternate weakly affected plots. The specific features of the effects of diamond, gold, and coalmining industries, as well as oil and gas field development, are discussed, which should be taken into account in sampling for bioindication. The problem of bioindication in the areas completely devoid of soil and plant cover can be solved by biotesting via assessment of bunching onion seed germination rate and the rate of mitotic aberrations. An increase in the FA level in trees and small mammals is observed in the areas transformed by the mining industry displaying a chronically increased radiation background and oil-polluted as a result of technogenic accidents. The use of FA index makes it possible to estimate the environmental quality and to compare the state of territories located under different natural and climatic conditions and influenced by multicomponent anthropogenic impacts differing in their strength and genesis, which interferes with their comparison. [ABSTRACT FROM AUTHOR]

The European golden jackal (Canis aureus moreoticus) is widespread in Bulgaria and it was assumed that the species had occupied almost the entire country with less manifested presence in highlands. The general aim of this investigation was to carry out comparative analysis at a population level of developmental stability of the jackal inhabiting in different habitats (POP_1, inhabiting Sakar-Strandzha region, POP_2 inhabiting the Upper Thracian Plain and POP_3 inhabiting the western part of the Sub-Balkan valleys), located along the presumable route of the species movement northwards and westwards in the country. The population levels of developmental stability were assessed through fluctuating asymmetry determined as minor non-directional deviations from bilateral symmetry in 10 morphological nonmetric skull characters. Looking at the fluctuating asymmetry as an indicator of environmental and genetic stress, there is no evidence of genetic depression by reproductive isolation in the studied populations. Moreover, there is no indication of relatively reduced developmental stability in any of the analyzed populations. In general, the results from the comparative population analysis of the craniological epigenetic fluctuating asymmetry in Bulgarian golden jackal with regard to the population developmental stability provided a substantial biological basis for their interpretation as biomonitor characteristics in a future biological monitoring of this species in the country. [ABSTRACT FROM AUTHOR]

Stress response is associated with increased activity in the hypothalamic–pituitary–adrenocortical axis. Chronic stress-induced elevation in cortisol may alter its own negative regulation with multiple long-term consequences for physical and psychological health. One of the most reliable physical traits associated with mental, apparent physical health, and competitiveness is the degree of facial fluctuating asymmetry. However, to our knowledge there are no studies regarding the relationship between cortisol levels, facial symmetry and male competitiveness, and how cortisol changes after a stressful test depending on these traits. Here, a group of 100 college men were photographed to obtain their facial asymmetry levels. They then, answered the perceived stress scale and the intrasexual competition test and donated two saliva samples (pre-and post-test sample) to measure the change in their cortisol levels after a stressful test. We found that basal cortisol levels were positively correlated with both perceived stress and competitiveness, but not with facial fluctuating asymmetry. Cortisol levels increased in most symmetrical men after a short stressful test, but it decreased in most asymmetrical men. The results suggest differences in endocrine responses according to facial fluctuating asymmetry in men and how these responses could be related to the maintenance of social status. [ABSTRACT FROM AUTHOR]

Developmental and functional abnormalities of the reproductive system of fishes are examined in connection with the changes in conditions of their existence, in particular, the anthropogenic influence. The author's own data and literature sources on abnormalities of gametogenesis and gonadogenesis in a number of sturgeon species in relation to anthropogenic pressure on the water bodies are analyzed, and their systematization is performed. It is shown that these abnormalities, which are disorders of the stability of development, can serve as indicators of the environmental health. [ABSTRACT FROM AUTHOR]

The study of the developmental stability in natural populations is a promising direction of population developmental biology, which opens new possibilities for estimation of the nature of the observed phenotypic diversity and understanding the mechanisms of population dynamics and microevolutionary transformations. This direction of the studies allows one to approach the estimation of the condition of natural populations. A special analysis of possible changes in the developmental stability indicators under different anthropogenic effects allows one to characterize this approach as one of the main within the methodology of the health of environment estimation based on the organism condition characteristics by the developmental homeostasis. The approach seems promising for the estimation and monitoring of the condition of natural populations of different species as well as for the environmental quality estimation. [ABSTRACT FROM AUTHOR]

Using the centipede model species Strigamia maritima as a subject of study, we illustrate the potential of geometric morphometrics for investigating the development and evolution of segmentation, with a specific focus on post-embryonic segmental patterning. We show how these techniques can contribute detailed descriptive data for comparative purposes, but also precious information on some features of the developmental system that are considered relevant for the evolvability of a segmented body architecture, such as developmental stability and canalization. Morphometric analyses allow to separately investigate several sources of phenotypic variation along a segmented body axis, like constitutive and random segment heteronomy, both within and among individuals. Specifically, in S. maritima , the segmental pattern of ventral sclerite shapes mirrors that of their bilateral fluctuating asymmetry and among-individual variation in associating the most anterior and most posterior segments in diverging from the central ones. Also, among segments, there seems to be a correlation between fluctuating asymmetry and shape variation among individuals, suggesting that canalization and developmental stability are somehow associated. Overall, these associations might stem from a joint influence of the segmental position on the two processes of developmental buffering. [ABSTRACT FROM AUTHOR]

Colour patterns (e.g. irregular, spotted or barred forms) are widespread in the animal kingdom, yet their potential role as signals of quality has been mostly neglected. However, a review of the published literature reveals that pattern itself (irrespective of its size or colour intensity) is a promising signal of individual quality across species of many different taxa. We propose at least four main pathways whereby patterns may reliably reflect individual quality: (i) as conventional signals of status, (ii) as indices of developmental homeostasis, (iii) by amplifying cues of somatic integrity and (iv) by amplifying individual investment in maintenance activities. Methodological constraints have traditionally hampered research on the signalling potential of colour patterns. To overcome this, we report a series of tools (e.g. colour adjacency and pattern regularity analyses, Fourier and granularity approaches, fractal geometry, geometric morphometrics) that allow objective quantification of pattern variability. We discuss how information provided by these methods should consider the visual system of the model species and behavioural responses to pattern metrics, in order to allow biologically meaningful conclusions. Finally, we propose future challenges in this research area that will require a multidisciplinary approach, bringing together inputs from genetics, physiology, behavioural ecology and evolutionary-developmental biology. [ABSTRACT FROM AUTHOR]

Fluctuating asymmetry (FA) in nine species of small mammals (Insectivora and Rodentia) was estimated using 10 cranial features (foramina for nerves and blood vessels). The main criterion was the occurrence of the fluctuating asymmetry manifestations (OFAM). A total of 2300 skulls collected in the taiga and forest-tundra of Yakutia (Northeast Asia) were examined. The examined species are characterized by comparable OFAM values in the vast territories of the taiga zone; on the ecological periphery of the range an increased FA level is registered. Asymmetric manifestations in analyzed features are equally likely to occur in males and females. OFAM values in juveniles are higher than in adults; this difference is more pronounced on the periphery of the geographic range. Among juveniles, lower FA levels are observed in individuals that have bred. It can be surmised that the risk of elimination of individuals with high FA levels increases in stressful periods (active reproduction and winter). In conditions that are close to optimal, populations demonstrate relatively homogeneous FA levels, while on the periphery of the area an increase in occurrence of disturbances in developmental stability is observed, which leads, on one hand, to higher average FA for the population and, on the other hand, to heterogeneity of the population in this parameter. [ABSTRACT FROM AUTHOR]

Fluctuating asymmetry (FA), random deviation from perfect bilateral symmetry, is an indicator of developmental stability. Examining the ontogeny of FA can illustrate whether symmetry is actively maintained as the organism grows or breaks down as perturbations accumulate with age. Previous studies of changes in human FA with age have been cross-sectional studies and give conflicting results. We analyzed data from a longitudinal study of bodily FA in Jamaicans, using a composite index of seven paired traits. In addition, 288 children (ages 5-12) were first measured in 1996, and many were re-measured in 2002 and 2006 (maximum age = 22 years). Both within-individual longitudinal comparisons and between-individual comparisons across age groups demonstrate changes in FA with age. In males and females, FA increased until around age 13, but the pattern of change differed between the sexes. In males, FA increased rapidly approaching adolescence and then slightly declined into early adulthood. The increase in female FA was more gradual and then leveled off. The patterns observed likely reflect accumulation of developmental errors over time, rapid physical changes during puberty (especially in boys), and then regulation of symmetry when transitioning into adulthood. Although most changes in symmetry over time probably reflect random processes, the magnitude and direction of asymmetry in an individual at one point in time tended to be positively (though weakly) related to asymmetry in later years, pointing to underlying differences among individuals in developmental stability. [ABSTRACT FROM AUTHOR]

Developmental stability and canalization describe the ability of developmental systems to minimize phenotypic variation in the face of stochastic micro-environmental effects, genetic variation and environmental influences. Canalization is the ability to minimize the effects of genetic or environmental effects, whereas developmental stability is the ability to minimize the effects of micro-environmental effects within individuals. Despite much attention, the mechanisms that underlie these two components of phenotypic robustness remain unknown. We investigated the genetic structure of phenotypic robustness in the collaborative cross ( CC) mouse reference population. We analysed the magnitude of fluctuating asymmetry ( FA) and among-individual variation of cranial shape in reciprocal crosses among the eight parental strains, using geometric morphometrics and a diallel analysis based on a Bayesian approach. Significant differences among genotypes were found for both measures, although they were poorly correlated at the level of individuals. An overall positive effect of inbreeding was found for both components of variation. The strain CAST/EiJ exerted a positive additive effect on FA and, to a lesser extent, among-individual variance. Sex- and other strain-specific effects were not significant. Neither FA nor among-individual variation was associated with phenotypic extremeness. Our results support the existence of genetic variation for both developmental stability and canalization. This finding is important because robustness is a key feature of developmental systems. Our finding that robustness is not related to phenotypic extremeness is consistent with theoretical work that suggests that its relationship to stabilizing selection is not straightforward. [ABSTRACT FROM AUTHOR]

ERP measures may index genetic risk for psychopathology before disorder onset in adolescence, but little is known about their developmental rank-order stability during this period of significant brain maturation. We studied ERP stability in 48 pairs of identical twins (age 14-16 years) tested 1 year apart. Trial-averaged voltage waveforms were extracted from electroencephalographic recordings from oddball/novelty, go/no-go, and flanker tasks, and 16 amplitude measures were examined. Members of twin pairs were highly similar, whether based on ERP amplitude measures (intraclass correlation [ICC] median = .64, range = .44-.86) or three factor scores (all ICCs ≥ .69) derived from them. Stability was high overall, with 69% of the 16 individual measures generating stability coefficients exceeding .70 and all factor scores showing stability above .75. Measures from 10 difference waveforms calculated from paired conditions within tasks were also examined, and were associated with lower twin similarity (ICC median = .52, .38-.64) and developmental stability (only 30% exceeding .70). In a supplemental analysis, we found significant developmental stability for error-related negativity (range = .45-.55) and positivity (.56-.70) measures when average waveforms were based on one or more trials, and that these values were equivalent to those derived from averages using the current field recommendation, which requires six or more trials. Overall, we conclude that the studied brain measures are largely stable over 1 year of mid- to late adolescence, likely reflecting familial etiologic influences on brain functions pertaining to cognitive control and salience recognition. [ABSTRACT FROM AUTHOR]

The g -loss predicted based on genetic selection is smaller than that observed across various ratio-scale measures of cognitive ability. The difference may result in part from the accumulation of deleterious mutations across generations, reducing g via their effects on developmental stability/fitness. Previously published secular trend data on a developmental stability measure, craniofacial fluctuating asymmetry (FA) size, for white US males and females covering 14 and 15 decades respectively, are re-analysed. When the secular increases in FA size are rescaled as declines in latent developmental stability, and multiplied by the validity and reliability adjusted developmental stability- g correlation, g -losses of −.16 points per decade are predicted for the males, females and the combined sample. Predicted fitness losses due to mutation accumulation may account for 30% of the generational decline (−.05 points per decade), indicating only a small role for mutations in secular g -loss. The remaining 70% (−.11 points per decade) may result from developmental stability disrupting environmental change, such as increased exposure to pollutants. Adding these to the g -loss due to selection (re-estimated at −.54 points per decade) yields a combined decadal loss of −.70 points. Additional adjustments for replacement migration and the generation length- g interaction yield a larger magnitude decadal g -loss of − 1.25 points. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the integral indicator for developmental stability, the fluctuating asymmetry (FA), in the marsh frog Pelophylax ridibundus populations that inhabit biotopes of different types (running rivers and still, dam lakes), when exposed to different types of anthropogenic pollution (domestic sewage pollution and heavy metal pollution) in south Bulgaria. A total of 920 P. ridibundus individuals were used for FA analyses over three years (2009-2011). Fluctuating asymmetry was defined by 10 morphological traits, using the index frequency of asymmetric manifestation of an individual (FAMI). In closed water basins, regardless of the nature of toxicants, the FA values in P. ridibundus populations were statistically lower than those in river populations. The FA values were constantly the highest under conditions of sustained anthropogenic pollution, with high concentrations of toxicants in rivers with domestic sewage pollution and heavy-metal pollution. The results provide better opportunities to use FA in P. ridibundus populations for bioindication and biomonitoring, and for parallel and independent analyses of the physicochemical assessment of the environmental condition. [ABSTRACT FROM AUTHOR]

Fluctuating asymmetry (FA) is defined as subtle deviations from perfect bilateral symmetry, evident in differences between the right and the left sides of any given trait. It is a pattern of variation between sides and measures developmental instability. Differences in the level of FA may be used for comparing developmental precision among closely related species and thus may give an idea whether developmental stability was affected during the divergence and separation of populations into distinct species. Keeping this in view, FA was studied in four species of the Drosophila bipectinata complex i.e. D. bipectinata, D. parabipectinata, D. malerkotliana and D. pseudoananassae. In females of all the four species, FA values did not vary significantly for any of the traits considered. However, in case of males, they varied significantly for Wing length (WL) and sex comb tooth number (SCTN). Also, while in females Composite fluctuating asymmetry (CFA) did not exhibit significant variation, in males it was found to vary significantly across the four species. However, Bonferroni t- tests did not reveal any consistent difference in FA levels between any two species. The magnitude of FA was found to differ significantly among traits and CFA values were found to be higher for males than females in all the four species. Therefore, it may be concluded that the level of FA shows trait specific variations and males are more prone to developmental perturbations. However, the FA levels are more or less similar in all the four species of this complex. Thus, developmental precision remains nearly same in all the four species of this complex irrespective of the degree of evolutionary divergence reached. [ABSTRACT FROM AUTHOR]

In animals, developmental stability is frequently assessed by the level of fluctuating asymmetry. Several environmental and genetic stress factors can increase the developmental instability in a population. Anyhow, the use of fluctuating asymmetry as a measurement of developmental instability and its relationship to other measurements of genetic and environmental stress, remain controversial. We studied this subject in the Balearic lizard, Podarcis lilfordi, and examined four populations inhabiting different coastal islets of Minorca (Balearic Islands, Spain). These populations show clear ecological and genetic differences that allowed us to study factors potentially determining the level of fluctuating asymmetry. We examined the following predictions: (1) fluctuating asymmetry will increase on smaller islands; (2) fluctuating asymmetry will increase on islands with a higher lizard density; (3) fluctuating asymmetry will increase on islands with more heavily parasitized lizards; and (4) populations with higher inbreeding levels would be more susceptible to environmental stress. Our results would partially support the fourth prediction of a higher fluctuating asymmetry in populations with lower genetic variability and, consequently, a higher inbreeding level. Probably, other environmental factors modulate this relationship. [ABSTRACT FROM AUTHOR]

The idea that symmetry in facial traits is associated with attractiveness because it reliably indicates good physiological health, particularly to potential sexual partners, has generated an extensive literature on the evolution of human mate choice. However, large-scale tests of this hypothesis using direct or longitudinal assessments of physiological health are lacking. Here, we investigate relationships between facial fluctuating asymmetry (FA) and detailed individual health histories in a sample (n = 4732) derived from a large longitudinal study (Avon Longitudinal Study of Parents and Children) in South West England. Facial FA was assessed using geometric morphometric analysis of facial landmark configurations derived from three-dimensional facial scans taken at 15 years of age. Facial FA was not associated with longitudinal measures of childhood health. However, there was a very small negative association between facial FA and IQ that remained significant after correcting for a positive allometric relationship between FA and face size. Overall, this study does not support the idea that facial symmetry acts as a reliable cue to physiological health. Consequently, if preferences for facial symmetry do represent an evolved adaptation, then they probably function not to provide marginal fitness benefits by choosing between relatively healthy individuals on the basis of small differences in FA, but rather evolved to motivate avoidance of markers of substantial developmental disturbance and significant pathology. [ABSTRACT FROM AUTHOR]

The value of fluctuating asymmetry is considered to be an indicator of the developmental instability of the organism. The consequences of activities of the mining industry facilities, which are characterized by alienation and transformation of large areas of natural landscapes, are analyzed as an anthropogenic factor. The objects of study were small mammals (northern red-backed ( Clethrionomys rutilus) and gray red-backed ( Clethrionomys rufocanus) voles, tundra vole ( Microtus oeconomus), Laxmann's ( Sorex caecutiens) and tundra ( S. tundrensis) shrews) and trees (Japanese white birch ( Betula platyphylla), Betula divaricate, Betula exilis, Duschekia fruticosa, and busket willow ( Salix viminalis)). In total, 3500 skulls and approximately 30000 leaves collected in the taiga zone of Yakutia were studied. The index of fluctuating asymmetry, as well as population parameters and composition of small mammal communities, were analyzed. The data on the value of the fluctuating asymmetry in the studied species in natural habitats are given. It is shown that, in natural conditions, this parameter can rise with deterioration in living conditions, particularly at the ecological periphery of the range. Anthropogenic transformation of natural landscapes creates an 'anthropogenic periphery' and causes changes similar to the adaptive responses at the northern limit of the distribution of species. It was found that, through pollution and disruption of ecosystems, the mining industry affects all levels of organization of the living matter, but the population and cenotic parameters give an unambiguous response only at macroanthropogenic transformations. Increase in the level of fluctuating asymmetry is the most sensitive indicator of anthropogenic impact and it should also be taken into account that disruptions in the developmental stability of an organism reflect the destructive processes occurring in the population and community. [ABSTRACT FROM AUTHOR]