Special Issue "Fluctuating Asymmetry 2016"

A special issue of Symmetry (ISSN 2073-8994).

Deadline for manuscript submissions: closed (31 August 2016).

Special Issue Editor

Prof. Dr. John H. Graham
E-Mail Website
Guest Editor
Department of Biology, Berry College, Mount Berry, Georgia, 30149, USA
Tel. +01 706290 2671; Fax: +01 706238 7855
Interests: fluctuating asymmetry; developmental instability; evolutionary genetics; hybrid zones; community ecology
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Special Issue Information

Dear Colleagues,

Fluctuating asymmetry is the random deviation from perfect symmetry in populations of organisms. It is a measure of developmental noise, which reflects a population’s average state of adaptation and coadaptation. Moreover, it often increases under both environmental and genetic stress. Researchers study fluctuating asymmetry as deviations from bilateral, radial, rotational, dihedral, translational, helical, and fractal symmetries. Fluctuating asymmetry is measured via traditional measures of dispersion (variances and mean absolute deviations), landmark methods for shape asymmetry, and continuous symmetry measures. It has numerous applications in evolutionary biology, quantitative genetics, environmental biology, ecotoxicology, conservation biology, anthropology, agriculture and aquaculture, evolutionary psychology, and medicine and public health.

The aim of this Second Special Issue on “Fluctuating Asymmetry” is to continue highlighting all aspects of fluctuating asymmetry in the biological sciences. Research papers, comprehensive reviews, and discussions of theory are especially welcome. However, any other kind of paper (communication, technical note, short overview, or comment) will also be taken into consideration.

Prof. Dr. John H. Graham
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • fluctuating asymmetry
  • directional asymmetry
  • antisymmetry
  • symmetry breaking
  • developmental noise
  • robustness
  • biological indicators
  • Darwinian fitness

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Published Papers (10 papers)

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Research

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Open AccessArticle
Morphometric Asymmetry of Frustule Outlines in the Pennate Diatom Luticola poulickovae (Bacillariophyceae)
Symmetry 2016, 8(12), 150; https://doi.org/10.3390/sym8120150 - 07 Dec 2016
Cited by 6
Abstract
Side orientation of cells is usually ambiguous in unicellular organisms, making it impossible to separate components of directional asymmetry (DA) and fluctuating asymmetry (FA). However, frustules of the diatom Luticola poulickovae have biradially symmetric outlines, and their central areas bear ornamentation that is [...] Read more.
Side orientation of cells is usually ambiguous in unicellular organisms, making it impossible to separate components of directional asymmetry (DA) and fluctuating asymmetry (FA). However, frustules of the diatom Luticola poulickovae have biradially symmetric outlines, and their central areas bear ornamentation that is asymmetric across the apical axis. The goal of this study was to explore differentiation of morphometric asymmetry across the apical axis into DA and FA components. Is there detectable DA of the valve outlines of two L. poulickovae strains that may be related to the asymmetric central areas? Given that the life cycle of diatoms involves cell-size diminution, and cell shape is strongly affected by allometry, we also explored the question of whether asymmetry is correlated with cell size. The extent of symmetric variation among individuals in each strain, as well as DA and FA across the apical axis, were quantified using two Procrustes ANOVA models. The results revealed no correlation of either total asymmetry or FA with valve size. DA was significant and considerably more pronounced than FA in both strains, indicating that there is previously unknown systematic asymmetry of valve outlines of L. poulickovae, which may be related to the asymmetry of its central area. Full article
(This article belongs to the Special Issue Fluctuating Asymmetry 2016)
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Open AccessArticle
Fluctuating Asymmetry of Craniological Features of Small Mammals as a Reflection of Heterogeneity of Natural Populations
Symmetry 2016, 8(12), 142; https://doi.org/10.3390/sym8120142 - 29 Nov 2016
Cited by 3
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Fluctuating Asymmetry 2016)
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Open AccessArticle
The Novel Concept of “Behavioural Instability” and Its Potential Applications
Symmetry 2016, 8(11), 135; https://doi.org/10.3390/sym8110135 - 18 Nov 2016
Cited by 3
Abstract
The concept of developmental instability (DI) is a well-known indicator of environmental and genetic stress and is often investigated using various indices such as fluctuating asymmetry, directional asymmetry, antisymmetry and phenotypic variance. Investigations dealing with DI are using morphometric traits. The aim of [...] Read more.
The concept of developmental instability (DI) is a well-known indicator of environmental and genetic stress and is often investigated using various indices such as fluctuating asymmetry, directional asymmetry, antisymmetry and phenotypic variance. Investigations dealing with DI are using morphometric traits. The aim of this investigation is to present the novel concept of behavioural instability in which the trait measured is a behavioural trait. We apply the conventional indices used for the estimation of developmental instability on directional movement—clockwise (CW) and counter-clockwise (CCW) movement of 19 highly inbred lines of Drosophila melanogaster tested in a circular arena. We show that it is possible to quantify behavioural instability using the indices traditionally used to investigate DI. Results revealed several significant differences among lines, depending on the index utilized. The perspectives of utilizing the concept in biological research such as toxicology, evolutionary and stress biology are discussed. Full article
(This article belongs to the Special Issue Fluctuating Asymmetry 2016)
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Open AccessFeature PaperArticle
Nutritional Stress Causes Heterogeneous Relationships with Multi-Trait FA in Lesser Black-Backed Gull Chicks: An Aviary Experiment
Symmetry 2016, 8(11), 133; https://doi.org/10.3390/sym8110133 - 17 Nov 2016
Abstract
Environmental stressors have the potential to induce perturbations in the development of young individuals, leading to aberrant and unstable development. This may manifest as fluctuating asymmetry (FA; small, non-directional changes in the bilateral symmetry of morphological traits). Although widely regarded as a proxy [...] Read more.
Environmental stressors have the potential to induce perturbations in the development of young individuals, leading to aberrant and unstable development. This may manifest as fluctuating asymmetry (FA; small, non-directional changes in the bilateral symmetry of morphological traits). Although widely regarded as a proxy for stress effects, the use of FA as a biomarker is still a topic of much debate. We investigated the applicability of FA as an indicator of nutritional stress (brought about by energetic constraints) by experimental manipulation of the diet composition and quantity during the growth of Lesser Black-backed Gull (Larus fuscus) chicks. FA as an endpoint was measured across the tarsus, wing and 10th primary feather when chicks reached 30 days of age. Although levels of asymmetry were found to increase with stress in the feather, relationships with tarsus and wing FA were mixed and mostly non-significant. Furthermore, we did not find any correlations in unsigned FA between traits, indicating the absence of organism-wide asymmetry. Our study was therefore unable to find unequivocal evidence in support of the application of FA as a reliable estimator of nutritional stress. Full article
(This article belongs to the Special Issue Fluctuating Asymmetry 2016)
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Open AccessArticle
Fluctuating Asymmetry in Two Common Freshwater Fishes as a Biological Indicator of Urbanization and Environmental Stress within the Middle Chattahoochee Watershed
Symmetry 2016, 8(11), 124; https://doi.org/10.3390/sym8110124 - 10 Nov 2016
Cited by 2
Abstract
Deviations in bilateral symmetry or fluctuating asymmetry of an organism may result under environmental stressors that reduce developmental homeostasis and stability. Anthropogenic stressors such as increased urbanization can negatively impact environmental quality of aquatic ecosystems. Researchers have stressed the value in finding easy, [...] Read more.
Deviations in bilateral symmetry or fluctuating asymmetry of an organism may result under environmental stressors that reduce developmental homeostasis and stability. Anthropogenic stressors such as increased urbanization can negatively impact environmental quality of aquatic ecosystems. Researchers have stressed the value in finding easy, accurate and inexpensive methods for assessing potential stress within ecosystems. Here we use fluctuating asymmetry (FA) as a useful quantitative tool in assessing the environmental quality and potential urban-based stressors within eight creeks of the Bull and Upatoi Creeks Watershed within the larger watershed of the Middle Chattahoochee. Using Geographic Information System (GIS), we characterize land-use patterns and a decreasing urbanization gradient as related to each creek’s eastward position from Columbus, Georgia. We collected two common fishes (redbreast sunfish; Lepomis auritus and bluegill; Lepomis macrochirus), measured both metric and meristic traits and investigated if the degree of FA in these two common fishes correlated with the urbanization gradient across creeks. We found significant differences in FA among creeks with one of the highest FA measures for the most urban creek. Principal component analysis (PCA) scores of urbanization and water chemistry were regressed against FA scores. We found no significant relationship between urbanization and FA nor environmental water chemistry and FA among creeks. We comment on the use of FA as a potential response variable and biological indicator of environmental stress within this watershed. Full article
(This article belongs to the Special Issue Fluctuating Asymmetry 2016)
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Open AccessFeature PaperArticle
A Longitudinal Study of Changes in Fluctuating Asymmetry with Age in Jamaican Youth
Symmetry 2016, 8(11), 123; https://doi.org/10.3390/sym8110123 - 09 Nov 2016
Cited by 6
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Fluctuating Asymmetry 2016)
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Open AccessArticle
Asymmetric Facial Bone Fragmentation Mirrors Asymmetric Distribution of Cranial Neuromasts in Blind Mexican Cavefish
Symmetry 2016, 8(11), 118; https://doi.org/10.3390/sym8110118 - 31 Oct 2016
Cited by 5
Abstract
Craniofacial asymmetry is a convergent trait widely distributed across animals that colonize the extreme cave environment. Although craniofacial asymmetry can be discerned easily, other complex phenotypes (such as sensory organ position and numerical variation) are challenging to score and compare. Certain bones of [...] Read more.
Craniofacial asymmetry is a convergent trait widely distributed across animals that colonize the extreme cave environment. Although craniofacial asymmetry can be discerned easily, other complex phenotypes (such as sensory organ position and numerical variation) are challenging to score and compare. Certain bones of the craniofacial complex demonstrate substantial asymmetry, and co-localize to regions harboring dramatically expanded numbers of mechanosensory neuromasts. To determine if a relationship exists between this expansion and bone fragmentation in cavefish, we developed a quantitative measure of positional symmetry across the left-right axis. We found that three different cave-dwelling populations were significantly more asymmetric compared to surface-dwelling fish. Moreover, cave populations did not differ in the degree of neuromast asymmetry. This work establishes a method for quantifying symmetry of a complex phenotype, and demonstrates that facial bone fragmentation mirrors the asymmetric distribution of neuromasts in different cavefish populations. Further developmental studies will provide a clearer picture of the developmental and cellular changes that accompany this extreme phenotype, and help illuminate the genetic basis for facial asymmetry in vertebrates. Full article
(This article belongs to the Special Issue Fluctuating Asymmetry 2016)
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Open AccessArticle
Associations between Floral Asymmetry and Individual Genetic Variability Differ among Three Prickly Pear (Opuntia echios) Populations
Symmetry 2016, 8(11), 116; https://doi.org/10.3390/sym8110116 - 29 Oct 2016
Cited by 3
Abstract
While stress is expected to increase developmental instability (DI), not all studies confirm this. This heterogeneity could in part be due to the use of subtle differences between the left and right side of bilateral symmetrical organisms to quantify DI, leading to large [...] Read more.
While stress is expected to increase developmental instability (DI), not all studies confirm this. This heterogeneity could in part be due to the use of subtle differences between the left and right side of bilateral symmetrical organisms to quantify DI, leading to large sampling error obscuring associations with DI. Traits that develop simultaneously more than twice (such as flower petals or bird feathers) reflect individual DI more reliably, such that stronger associations are expected to emerge. Furthermore, some studies have shown differences in strengths of associations among populations. We studied the association between individual genetic diversity and DI in flower petals within three Opuntia echios populations inhabiting Galápagos. Quantifying individual DI through variation in length and width of a high number of petals within individual cacti, lead to a strong association between DI and genetic diversity in one population. We conclude that associations between individual DI and genetic diversity can be more easily revealed by measuring traits that develop repeatedly. Full article
(This article belongs to the Special Issue Fluctuating Asymmetry 2016)
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Open AccessArticle
Maternal Stress Affects Fetal Growth but Not Developmental Instability in Rabbits
Symmetry 2016, 8(10), 101; https://doi.org/10.3390/sym8100101 - 27 Sep 2016
Cited by 1
Abstract
Developmental instability (DI), often measured by fluctuating asymmetry (FA) or the frequency of phenodeviants (fPD), is thought to increase with stress. However, specifically for stressors of maternal origin, evidence of such negative associations with DI is scarce. Whereas effects of maternal stress on [...] Read more.
Developmental instability (DI), often measured by fluctuating asymmetry (FA) or the frequency of phenodeviants (fPD), is thought to increase with stress. However, specifically for stressors of maternal origin, evidence of such negative associations with DI is scarce. Whereas effects of maternal stress on DI have predominately been examined retroactively in humans, very little is known from experiments with well-defined stress levels in animal model systems. The aim of this study was to examine the effects of maternal exposure to three doses (plus a control) of a toxic compound affecting maternal condition on DI of their offspring in rabbits. Presence of maternal stress induced by the treatment was confirmed by a decrease in food consumption and weight gain of gravid females in the medium and high dose. Major abnormalities and mortality were unaffected by dose, suggesting the lack of toxic effects of the compound on the offspring. In spite of string maternal stress, offspring FA did not increase with dose. The treatment did lead to elevated fPD, but most were transient, reflecting growth retardation. Furthermore, a consistent association between fPD and FA was absent. These findings indicate that DI is not increased by maternal stress in this animal model. Full article
(This article belongs to the Special Issue Fluctuating Asymmetry 2016)
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Review

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Open AccessReview
Fluctuating Asymmetry of Human Populations: A Review
Symmetry 2016, 8(12), 154; https://doi.org/10.3390/sym8120154 - 16 Dec 2016
Cited by 15
Abstract
Fluctuating asymmetry, the random deviation from perfect symmetry, is a widely used population-level index of developmental instability, developmental noise, and robustness. It reflects a population’s state of adaptation and genomic coadaptation. Here, we review the literature on fluctuating asymmetry of human populations. The [...] Read more.
Fluctuating asymmetry, the random deviation from perfect symmetry, is a widely used population-level index of developmental instability, developmental noise, and robustness. It reflects a population’s state of adaptation and genomic coadaptation. Here, we review the literature on fluctuating asymmetry of human populations. The most widely used bilateral traits include skeletal, dental, and facial dimensions; dermatoglyphic patterns and ridge counts; and facial shape. Each trait has its advantages and disadvantages, but results are most robust when multiple traits are combined into a composite index of fluctuating asymmetry (CFA). Both environmental (diet, climate, toxins) and genetic (aneuploidy, heterozygosity, inbreeding) stressors have been linked to population-level variation in fluctuating asymmetry. In general, these stressors increase average fluctuating asymmetry. Nevertheless, there have been many conflicting results, in part because (1) fluctuating asymmetry is a weak signal in a sea of noise; and (2) studies of human fluctuating asymmetry have not always followed best practices. The most serious concerns are insensitive asymmetry indices (correlation coefficient and coefficient of indetermination), inappropriate size scaling, unrecognized mixture distributions, inappropriate corrections for directional asymmetry, failure to use composite indices, and inattention to measurement error. Consequently, it is often difficult (or impossible) to compare results across traits, and across studies. Full article
(This article belongs to the Special Issue Fluctuating Asymmetry 2016)
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