Natural genetic variation in fluctuating asymmetry of wing shape inDrosophila melanogaster

Abstract

18Fluctuating asymmetry (FA), defined as random deviation from perfect symmetry, has been used to 19 assay the inability of individuals to buffer their developmental processes from environmental 20 perturbations (i.e., developmental instability). In this study, we aimed to characterize the natural 21 genetic variation in FA of wing shape in Drosophila melanogaster, collected from across the 22 Japanese archipelago. We quantified wing shapes at whole wing and partial wing component levels 23 and evaluated their mean and FA. We also estimated the heritability of the mean and FA of these 24 traits. We found significant natural genetic variation in all the mean wing traits and in FA of one of 25 the partial wing components. Heritability estimates for mean wing shapes were significant in two 26 and four out of five wing traits in males and females, respectively. On the contrary, heritability 27 estimates for FA were low and not significant. This is a novel study of natural genetic variation in 28 FA of wing shape. Our findings suggest that partial wing components behave as distinct units of 29 selection for FA, and local adaptation of the mechanisms to stabilize developmental processes occur 30 in nature. 31 32

Analyzing Fluctuating Asymmetry with Geometric Morphometrics: Concepts, Methods, and Applications

“…Quantitative genetic analyses for fluctuating asymmetry of shape have obtained low estimates of heritability sometimes statistically indistinguishable from zero [85,128]. This agrees with findings from traditional measurements [388].…”

“…Results from statistical models suggest that these findings are in line with theoretical expectations and that it is very challenging to estimate the heritability of the developmental instability that underlies the observed fluctuating asymmetry with the sizes of experiments that are normally used [389]. Experiments comparing fluctuating asymmetry among inbred strains have regularly found significant differences, and therefore indicate that there is a genetic basis to fluctuating asymmetry for the shape of Drosophila wings [56,85] and mouse skulls [135].…”

“…A few studies of shape in Drosophila found no significant directional asymmetry of wing shape [115][116][117][118][119] or mixed results [120][121][122][123][124][125][126], although a series of other studies did find it [15,16,54,56,62,77,85,123]. Similarly, one study on human skulls [127] found no directional asymmetry of shape, whereas several others reported directional asymmetry of the skull [47,68,84,86,90,94,109] and soft tissues of the face and ears [38,66,98,104,105,108].…”

“…Genetic studies of fluctuating asymmetry are complicated by the fact that the measurable asymmetries themselves are of non-genetic nature: what is of interest, therefore, is the genetic basis of developmental instability, the tendency of organisms with particular genotypes and in the given environment to produce left-right asymmetry. The most direct way to implement experiments that reflect this situation is to use model organisms where it is easy to obtain many individuals with identical genotypes [52,56,77,[124][125][126], but traditional approaches from quantitative genetics can also be used, such as parent-offspring regression [128], analyses of variation among inbred lines [85], or pedigree-based methods [85].…”

Offspring of older parents are smaller—but no less bilaterally symmetrical—than offspring of younger parents in the aquatic plant Lemna turionifera

“…Fluctuating asymmetry is the random, nondirectional departure from bilateral symmetry that occurs during many organisms’ development (Van Valen, ; see recent review by Graham, Raz, Hel‐Or, & Nevo, ). Such departures may reflect underlying developmental instability stemming from genetic effects (e.g., Tsujino & Takahashi, ) or environmental stress (e.g., Beasley, Bonisoli‐Alquati, & Mousseau, ). Just as older parents, when experiencing general age‐related physiological deterioration, may produce shorter‐lived, lower‐reproducing, and smaller offspring, so too can we hypothesize that they may be less able to produce bilaterally symmetrical offspring, compared to their younger counterparts.…”