Fluctuating asymmetry in leaves and flowers of sympatric species in a tropical montane environment

Fluctuating asymmetry (FA) represents small, random variations in traits, presumably with bilateral symmetry, and is widely used as a tool to measure developmental instability in plants and animals. Because FA is a quick, simple and reliable measure, it has been frequently used for monitoring levels of environmental stress. This study investigated whether FA can be used as a predictor of individual developmental instability for four sympatric Melastomataceae species. To achieve that aim, 20 individuals of Trembleya laniflora, T. parviflora, Lavoisiera campos‐portoana and Tibouchina heteromalla were marked in southeastern Brazil and monitored before and during the flowering season. The FA index was calculated as the mean of the difference in the width or length between the left and right sides measured for each leaf or flower. All studied species exhibited asymmetry in the leaves and flowers, but the leaves of L. campos‐portoana and the petal width of T. heteromalla exhibited directional asymmetry, also an indicator of developmental instability. The highest level of leaf asymmetry was found in T. heteromalla and on flowers of L. campos‐portoana. None of the studied species exhibited a significant relationship between the FA level of the leaves and flowers on an individual basis, indicating that environmental and/or genetic sources of stress might act differently on different plant traits. For the studied species, measurements of FA can be suggested as useful tools to biomonitor levels of stress experienced by both leaves and flowers within the Melastomataceae family.     

Fluctuating dental asymmetry as a measure of odontogenic canalization in man

Fluctuating odontometric asymmetry was evaluated in 202 Lengua Indians and in 125 contemporary caucasoids using Euclidean map analyses, rescaled asymmetry values, and Naperian logarithmic transformations. Both populations showed bimodal distributions of canalizing ability, with significantly more Lengua Indians being less well canalized. Student t-tests indicated that significant interpopulation differences in rescaled asymmetry values centered around maxillary mesiodistal dimensions. Analyses of variance failed to show significant levels of sexual dimorphism in the magnitude of asymmetry for both populations. It is concluded that even in a relatively stress-free population, there exist some individuals who are less well canalized than others. When a population is subjected to elevated levels of parasitic and nutritional stress, the number of less-well-canalized individuals increases significantly.     

Fluctuating asymmetry and aggression in boys

Fluctuating asymmetry (FA) is small deviations from perfect symmetry in normally bilaterally symmetrical traits. We examined the relationship between FA of five body traits (ear height, length of three digits, and ankle circumference) and self-reported scores of physical and verbal aggression in a sample of 90 boys aged 10 to 15 years. The relationships between FA and scores of aggression (particularly physical aggression) were found to be negative; in other words, the most symmetrical boys showed highest aggression. One trait (ankle circumference) showed the characteristics of “ideal” FA—parametric mean of zero and a normal distribution. Mean asymmetries calculated from six repeated measures of ankle FA in 30 subjects taken over a period of five months showed strong negative associations with scores of physical aggression which were independent of age, height, and weight. It is argued that soft tissue “cyclical” FA (as opposed to “fixed” bony FA) is dependent on the secretion of hormones: for example, cortisol. Causal associations between behavioral traits such as aggresion and hormones will lead to similar correlations between FA and behavior. John Manning is a senior lecturer in the School of Biological Sciences at the University of Liverpool. His research interests are in symmetry as an indicator of good genes, disease resistance, fertility, and hormonal status in human and nonhuman animals. Daniel Wood has a B.Sc. in anatomy and biology from Liverpool University. At present he is a postgraduate student in the School of Biological Sciences. His research interests are in fluctuating asymmetry and its behavioral correlates in adolescent boys.     

Fluctuating asymmetry as a possible measure of developmental homeostasis in humans: a review

We investigate three hypotheses related to fluctuating asymmetry (FA) of bilateral morphologic traits in humans: (1) the magnitude of FA in individual suffering from different levels of morbidity is significantly elevated compared with FA in healthy control subjects, (2) FA is negatively correlated with an individual's heterozygosity, and (3) phenotypic variance of FA may have a significant genetic component (or at least a family resemblance). Our experimental data and the literature support the first hypothesis and indicate that individuals who suffer from chromosomal or polygenic morbidity and from anomalies or conditions of development with still unknown genetic components demonstrate an elevated FA of various structures. The literature regarding the second hypothesis is sparse but is generally in agreement with it, although some exceptions exist. A study of correlations of phenotypic scores of FA between family members of nuclear families in two independent samples has shown that FA variance in individual traits probably does not have any significant genetic component. However, phenotypic variance of the mean estimate of FA over 8 traits showed significant additive and nonadditive (dominance) genetic components, each about 0.30.     

Fluctuating asymmetry and immune function in a field cricket

Recently, fluctuating asymmetry (FA) of morphological traits has attracted great attention as a short-cut measure of individual quality. Whereas there is some evidence that FA of sexual ornaments is negatively associated with immune function, studies concerning FA and immune function in non-ornamental traits are absent. Here, we tested whether FA of three non-ornamental traits in hind limbs is related to male immune function in a population of the Mediterranean field cricket, Gryllus bimaculatus. As different measures of male immune function, we used encapsulation rate and lytic activity. We found that a composite measure of FA (cFA) was negatively related to encapsulation rate. However, lytic activity was not related to cFA, but there was a tendency that males with higher body mass had higher lytic activity than males with lower body mass. Our results suggest that FA in non-ornamental traits indicates male immunocompetence in G. bimaculatus .     

Fluctuating asymmetry and fitness in Drosophila melanogaster

Models predict that developmental stability measured by fluctuating asymmetry should be positively correlated with fitness. Although such a correlation has often been suggested by indirect studies, there is still a lack of direct experimental evidence. In this note, I have measured the fluctuating asymmetry of sternopleural bristle counts in 32 lines of Drosophila melanogaster sharing the same genetic background but displaying all combinations of five visible mutations. Fluctuating asymmetry was heterogeneous among lines, suggesting a direct impact of the mutations on developmental stability. Two measures of fitness were made for each line: productivity (a combined measure of fecundity and egg‐to‐adult survivorship) and competitive male mating success. Fluctuating asymmetry was correlated with neither of these two components of fitness. This suggests that generalizations about fluctuating asymmetry must be taken with care.     

Fluctuating asymmetry and exogenous stress in fishes: a review

Fluctuating asymmetry (FA), which has been examined in a variety of plants and animals, is widely promoted as a useful bioindicator of exogenous stressors in habitats, whether of natural or anthropogenic origin. Wildlife managers and researchers often use a specific group of organisms as an indicator of the health of a given habitat. The purpose of this review is to demonstrate that FA can be an effective fish biomonitoring tool by presenting a vote counting meta-analysis of 81 fish FA studies published between 1966 and the first half of 2009. The vote counts were analyzed with the G test for independence to determine whether the probability of observing significant morphological asymmetry is determined by character type, exogenous stressor type, or fish order. The information obtained from these papers and their analysis is then used to outline areas in which FA studies can be improved: (1) carefully considering character choice; (2) distinguishing between asymmetry types; (3) determining the level of measurement error in between-sides character variation; (4) determining baseline FA levels in populations; (5) increasing the number of laboratory studies which corroborate field observations of FA; (6) conducting true replications of studies to validate previous findings. Only with more critical experimental design and data analysis can FA be used as a powerful tool for assessing environmental degradation.     

Genetic monitoring as a promising tool for conservation and management

In response to ever-increasing anthropogenic changes to natural ecosystems, regional, national and international organizations have established guidelines for monitoring biological diversity. Most monitoring programs, however, do not take full advantage of the potential afforded by molecular genetic markers, which can provide information relevant to both ecological and evolutionary time frames, while costing less and being more sensitive and reliable than traditional monitoring approaches. As several molecular and computational approaches are relatively new, many technical and theoretical issues remain to be resolved. Here, we illustrate how DNA and population genetic data can provide valuable information, often unattainable via other approaches, for monitoring species of management, conservation and ecological interest.     

洞穴型蝙蝠的栖息环境选择、生态作用及保护

多数蝙蝠为洞穴型。在野外调查的基础上,结合前人调查的结果,对洞穴型蝙蝠的栖息环境选择及其在洞穴生态系统中的特殊生态作用进行了探讨。针对目前随着人类活动的增加,洞穴型蝙蝠的生存环境遭到日益严重的干扰、破坏和污染而导致蝙蝠的物种多样性降低,加之国内对洞穴型蝙蝠研究不足的现状,提出了加强对洞穴型蝙蝠的栖息和捕食环境进行保护、对蝙蝠的多样性进行调查的建议。     

Fluctuating asymmetry in fetuses of diabetic rhesus macaques

This study examines dental fluctuating asymmetry (FA) in two samples of fetal rhesus monkeys, one composed of 19 fetuses from diabetic mothers (FDM) and the other of 20 fetuses from nondiabetic mothers. Seventeen measurements were taken on the deciduous dentition of right and left mandibles. The degree of FA was assessed by comparing FDM to fetuses of normal mothers by correlation between right and left sides, and analysis of variation differences between right and left sides. Significant FA was found for three traits based on the correlation between right and left sides and for seven traits by the between-treatment ratio of variance between sides. Distal teeth, both within and outside of a morphologic field, exhibit significantly greater FA than mesial teeth. Our results support the hypothesis that developmental instability is detectable by dental FA.     

Cryptic species as a window on diversity and conservation

The taxonomic challenge posed by cryptic species (two or more distinct species classified as a single species) has been recognized for nearly 300 years, but the advent of relatively inexpensive and rapid DNA sequencing has given biologists a new tool for detecting and differentiating morphologically similar species. Here, we synthesize the literature on cryptic and sibling species and discuss trends in their discovery. However, a lack of systematic studies leaves many questions open, such as whether cryptic species are more common in particular habitats, latitudes or taxonomic groups. The discovery of cryptic species is likely to be non-random with regard to taxon and biome and, hence, could have profound implications for evolutionary theory, biogeography and conservation planning.     

Fluctuating asymmetry and behavior in the ultimatum game in Jamaica

The ultimatum game measures cooperative tendencies in humans under experimental conditions. One individual can split money between oneself and another, while the other has the option of accepting or rejecting the offer, with each player receiving the accepted split or nothing if the split is rejected. We studied the association of players' degree of symmetry [fluctuating asymmetry (FA)] with behavior in the ultimatum game. Symmetrical males were expected to be less cooperative and, thus, make lower offers (while being more likely to reject unfair offers). In a population of young adult Jamaicans, who are well-characterized for bodily symmetry, we found that symmetrical males made significantly lower offers than asymmetrical ones (p<.001), but found no effect on rejection rates (perhaps due to a very small sample size). No significant association of symmetry and game playing was found in women, but women with a higher body mass index made less generous offers (p<.05).     

Bayesian Belief Networks as a tool for evidence-based conservation management

Effective conservation management is dependent on accessing and integrating different forms of evidence regarding the potential impacts of management interventions. Here, we explore the application of Bayesian Belief Networks (BBN), which are graphical models that incorporate probabilistic relationships among variables of interest, to evidence-based conservation management. We consider four case studies, namely: (i) impacts of deer grazing on saltmarsh vegetation; (ii) impacts of burning on upland bog vegetation; (iii) control of the invasive exotic plant Rhododendron ponticum; and (iv) management of lowland heathland by burning. Each of these themes is currently a significant conservation issue in the UK, and yet the potential outcomes of management interventions are poorly understood. Through these examples, we demonstrate that BBNs can be used to integrate and explore evidence from a variety of sources, including expert opinion and quantitative results from research investigations. Incorporation of such information in BBNs enables different sources of evidence to be compared, the potential impacts of management interventions to be explored and management trade-offs to be identified. BBNs also offer a highly visual tool for communicating the uncertainty associated with potential management outcomes to conservation practitioners, and they can also be readily updated as new evidence becomes available. Based on these features, we suggest that BBNs have outstanding potential for supporting evidence-based approaches to conservation management.     

Fluctuating asymmetry and survival ability in the forest tent caterpillar mothMalacosoma disstria: implications for pest management

Fluctuating asymmetry of the first tarsal segment of the proleg of the forest tent caterpiller mothMalacosoma disstria Hbn. (Lepidoptera: Lasiocampidae) was significantly inversely related to survival ability in the lab. The monitoring of population levels of fluctuating asymmetry could have important implications in pest management of this and other species by providing an indication of the health of a population.     

Population as a conservation and management unit in vertebrate animals

Under discussion are such population groups as management unit (stock) and evolutionarily significant unit, along with the problem of short-term ans long-term goals of conservation activities and wildlife management. The short-term goals may differ from the long-term goals. Management units (stocks) are demographically independent populations, though genetically they may be interconnected to a high degree. It is at this level of population organization that the short-term nature management goals are reached: the preservation of stable reproduction of management units, and the exclusion of excessive pressure on small groups. The evolutionarily significant units have independent conservation status determined by significant reproductive isolation and unique adaptations. It is at this level that long-term management goals are reached: the conservation of the native population structure, the evolutionarily significant differences, the maximum genetic diversity, and, thus, the evolutionary potential.     

Fluctuating asymmetry for specific bristle characters in Notch mutants of Drosophila melanogaster

Asymmetry has been used as a measure of developmental stability for bilaterally symmetrical organisms. Most studies have failed to partition the genetic and environmental contributions to the asymmetry phenotype due to the limitations of the systems used or the shortcomings in experimental design. The Notch mutants of Drosophila melanogaster were used to study the genetic contribution to asymmetry for six different bristle characters. Asymmetry response was character specific for the mutants examined. For N ^spl, N ^Co, N ^264–47, Ax ^71d, Ax ^9B2, Ax ^E2, l(1)N ^B and nd ² significant asymmetry responses, relative to wildtype Canton‐S, were observed for some characters. N ^60g11 and nd ¹ did not exhibit significant asymmetry for any of the characters examined. All of the mutants except N ^60g11 and nd ¹ showed thoracic bristle asymmetry. However, when asymmetry scores were pooled over the five bristle characters which individually exhibited fluctuating asymmetry, no significant differences were found between any genotypes. Therefore pooling asymmetry values across characters obscures the significant character specific asymmetry values observed. Thus caution is necessary when using the asymmetry phenotype of specific characters to draw organism wide conclusions about developmental stability. This revised version was published online in July 2006 with corrections to the Cover Date.     

Fluctuating asymmetry in hybrids of sibling species, Drosophila ananassae and Drosophila pallidosa, is trait and sex specific

Due to inconsistent results of the empirical studies, the relationship between fluctuating asymmetry (FA, a measure of developmental stability) and interspecific hybridization has been the subject of intense debates. In the present study, we have assessed the impact of interspecific hybridization between 2 sibling species of Drosophila: Drosophila ananassae and Drosophila pallidosa on the levels of FA over 3 generations. Trait size of different morphological traits, namely, sternopleural bristle number, wing length (WL), wing to thorax (W/T) ratio, sex comb tooth number (SCTN), and ovariole number differed significantly among parental species and their hybrids of different generations in both the sexes. However, the levels of FA of different morphological traits were similar in parental species and their hybrids of different generations in males (except SCTN) and in females (except for WL and W/T ratio). These results are interpreted in terms of developmental stability as a function of a balance between the level of heterozygosity and the disruption of coadapted gene complexes.     

Fluctuating asymmetry in mice and rats: evaluation of the method

Fluctuating asymmetry, which reflects small, random deviations from symmetry in otherwise bilaterally symmetrical characters, may be used as an indicator of developmental instability in humans and farm animals, and it may also be applicable as a stress indicator. We intended to find a method to allow the use of fluctuating asymmetry as a stress indicator in laboratory animals. That method had to be reproducible and reliable. Furthermore, its applicability in laboratory animals would be improved if it was possible to obtain measurements on the skin surface that correlated with results obtained by measuring the skeleton directly. Seven traits in mice and five traits in rats were evaluated for their applicability for measuring fluctuating asymmetry in mice and rats. Two out of the seven traits, i.e. the width of the joint between the third metatarsal bone and the digital bone on the hind paw, and the length of the incisor tooth at the top, were found to be reliable and reproducible for detecting fluctuating asymmetry in mice as well as in rats. Three out of the seven traits, i.e. the width of the carpal bones, the width of the joint between the tibia and the tarsal bones, and the length of the incisor tooth at the bottom, did express fluctuating asymmetry, but showed a poor day-to-day reproducibility. If the day-to-day reproducibility could be increased, these three traits might also be suitable for measuring fluctuating asymmetry in mice and rats. The last two traits, i.e. the length of ulna and the length of calcaneus plus metatarsal bone i.v., measured both on the skin surface and directly on the bone, did not express fluctuating asymmetry, and had a poor day-to-day reproducibility. These two traits are not suitable for measuring fluctuating asymmetry in mice and rats.