Variation patterns of bilateral characters: variation among characters and among populations in the White Sea herring, Clupea pallasi marisalbi (Berg) (Clupeidae, Teleosti)

Phenotypic variation in two populations of the White Sea herring Clupea pallasi marisalbi (Berg) (spring spawners and summer spawners), based on 21 meristic and 21 morphometric bilateral characters, has been studied. Total phenotypic variance was partitioned into a within-individual or stochastic component (fluctuating asymmetry) and an among-individual or factorial component, reflecting heterogeneity among individuals and resulting from the diversity of genotypes and environments. Both standardized stochastic and factorial components show clear negative correlations with means across characters. Negative correlation of the factorial components with means is in contradiction to the commonly accepted explanation of negative means-standardized variances association. Slopes of regression of standardized stochastic variances on means in meristic characters was significantly higher in summer spawners than in spring spawners, and results in discordance of stochastic variance across characters: it is higher in spring spawners for low and average variability characters and does not differ for both populations for high variability characters. The populations do not show notable differences in variation of morphometric characters. Consideration of other available data on these populations, such as spawning behaviour and salinity resistance of larvae, suggests that the lower slope of regression of stochastic variances on means is associated with the reduced viability of spring spawners     

Estimation of Developmental Stability of Small-Leaved Lime on Reserved and Urbanized Territories

The developmental stability of small-leaved lime (Tina cordata Mill.) was estimated in populations on territories of the Kerzhenskii State Nature Reserve, Nizhni Novgorod District, and in an industrial region of Nizhni Novgorod. The developmental stability was estimated according to the fluctuating asymmetry of the leaf measurements. The results obtained suggest that, in the urbanized territory, the homeostatic developmental mechanisms are weakened, as expressed in the increased degree of leaf asymmetry.     

Facial fluctuating asymmetry is not associated with childhood ill-health in a large British cohort study

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.     

Patterns of leaf asymmetry changes in Plantago major L. (ssp. major) natural populations exposed to different environmental conditions

In the present study, developmental stability of leaf traits was examined in three natural populations of Plantago major L. (ssp. major), representing two polluted environments (Karaburma and Zemun) and an unpolluted area (Crni Lug). Developmental stability was assessed as fluctuating asymmetry (FA). The magnitude of FA is believed to reflect differences in the ability of individuals to buffer their development in natural populations. We hypothesized that there are differences within characters and among characters in response to environmental conditions. Significant patterns of asymmetry correlations and asymmetry changes were detected both within characters and between characters. The manova results revealed a significant effect of individual and a significant individual × environment interaction on actual asymmetry (logL_i ? logR_i) and on the amount of asymmetry |(logL_i ? logR_i)| for leaf width and vein distances within a leaf. Over time, statistically significant and positive correlations of the FA values were detected for each trait separately per sample (population). For both leaf traits, there were differences for (logL_i ? logR_i) and |(logL_i ? logR_i)| asymmetry values among individuals within samples in response to yearly variations. Statistically significant and negative correlations for (logL_i ? logR_i) versus |(logL_i ? logR_i)| asymmetries were detected for both leaf traits. In summary, our results highlight the importance of differences in the ability of individuals to buffer their development under different environmental conditions and point to the concept that developmental stability is character specific.     

Within-individual changes in developmental stability affect flight performance

Developmental stability, as measured by fluctuating asymmetry,has been purported to be an indicator of individual quality,and low asymmetry can be selected for by sexual selection processes.However, low asymmetry can also arise due to biomechanical constraintsoperating on trait design, as it is predicted that asymmetrywill decrease mechanical efficiency. Specifically, it has beenpredicted that wing length asymmetry will be negatively relatedto avian flight performance. To date, empirical investigationshave only studied the influence of increasing asymmetry beyondnaturally occurring average values. I examined the influenceof within-individual changes in primary feather developmentalstability on flight performance in European starlings by studyingasymmetry and flight before and after wing molt. Individualsthat exhibited a decrease in wing asymmetry through molt experiencedincreased aerodynamic performance in terms of both angle oftakeoff and level flapping-flight speed. Birds that increasedwing asymmetry suffered a decrease in flight performance. Takeoffspeed and the ability to negotiate an aerial obstacle coursewere unaffected by asymmetry. My data provide empirical supportfor the predicted influence of wing asymmetry on flight, eventhough the changes in asymmetry were very small (mean = 0.47%of trait size) and further indicate the importance of biomechanicalconsiderations in any study of developmental stability     

Correlated development, organism‐wide asymmetry and patterns of asymmetry in two moth species

Understanding the mechanisms that determine the development of a bilaterally symmetrical trait is crucial to the interpretation of patterns of fluctuating asymmetry (FA). Experimental and theoretical studies have indicated that feedback mechanisms both within and between developing traits, may participate in the developmental control of asymmetry. This study provides evidence that naturally occurring patterns of FA are affected by interactions between different traits. We found positive between‐trait correlations in signed FA values for tibia lengths on different legs, but not between wing and tibia FA in two moth species. Further research should investigate if trait functionality is related to this presumed correlated development. An extension of the Rashevsky–Turing model of morphogenesis further showed that correlations between the signed FA values can be generated by feedback mechanisms that regulate growth patterns between traits. We argue that such feedback mechanisms can be expected to be widespread and show that between‐trait correlations in the unsigned FA then become confounded with correlations in the signed FA. In addition, correlated development appeared to invalidate the use of the hypothetical repeatability to translate correlations between the unsigned FA values into correlations in the presumed underlying developmental instability. In conclusion, the presence of an organism‐wide asymmetry, which are most frequently found in morphologically integrated traits, may be even less common than previously thought. This revised version was published online in July 2006 with corrections to the Cover Date.     

POPULATION AND DEVELOPMENTAL VARIATION IN THE FEATHER TIP

Variation among adults reflects variation in basic developmental processes, such as cell division rate. Partitioning the variation into its developmental components would be a major step in understanding evolutionary constraints, but is far from being achieved for any character. In this paper, we examine population variation in the feather tip, a useful structure to study because the history of development is recorded in the adult form. Our goal is to document the variability, and provide a developmentally based explanation for the level of variation observed. Using feathers collected from chicks of a small warbler, we partition population variation into variation attributed to accidents of development (through a consideration of fluctuating asymmetry), and among- and within-family components. Population variation in the earliest formed part of the feather is high (the coefficient of variation is c. 30%); population variation in later formed parts of the feather is lower. The among-individual and developmental noise components are both reduced in later formed parts, but there are differences in the way the two components are associated among the feather parts. The early and later formed parts are highly integrated at the among-individual level (correlations ≈ 1.0) but not at the developmental noise level (correlations ≈ 0.5). This suggests that at least two basic developmental processes are involved in determining the length of the various feather parts. We review feather development and pattern formation models to demonstrate that at least two developmental processes are indeed involved in feather growth. We show how these processes could interact to achieve the relative invariance in the later formed parts of the feather.