Morphometrical evolution in a Drosophila clade: the Drosophila obscura group (original) (raw)
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Genetika
Darwinian theory of evolution states that, evolution occurs through the natural selection. Therefore, demonstration of natural selection in nature is the central aim of many evolutionary studies and selection acts primarily at the phenotypic level because it is well known that phenotypic traits are the primary target of natural selection. While keeping this in view, we have studied certain morphometric traits in the sibling species pair, D. ananassae and D. pallidosa to test intra- and interspecific variations. The traits studied are wing length, thorax length, ratio of wing length and thorax length, sternopleural bristle number, ovariole number and sex-comb tooth number. In females of D. ananassae, significant strain differences were found for all the traits except ovariole number. In males, significant strain differences were found for all the traits. On the other hand, in D. pallidosa, significant strain differences were found for all the traits in both, males and females. The va...
Evolution of sexual dimorphism of wing shape in the Drosophila melanogaster subgroup
BMC Evolutionary Biology, 2009
Background Sexual dimorphism of body size has been the subject of numerous studies, but few have examined sexual shape dimorphism (SShD) and its evolution. Allometry, the shape change associated with size variation, has been suggested to be a main component of SShD. Yet little is known about the relative importance of the allometric and non-allometric components for the evolution of SShD. Results We investigated sexual dimorphism in wing shape in the nine species of the Drosophila melanogaster subgroup. We used geometric morphometrics to characterise wing shape and found significant SShD in all nine species. The amount of shape difference and the diversity of the shape changes evolved across the group. However, mapping the divergence of SShD onto the phylogeny of the Drosophila melanogaster subgroup indicated that there is little phylogenetic signal. Finally, allometry accounted for a substantial part of SShD, but did not explain the bulk of evolutionary divergence in SShD because allometry itself was found to be evolutionarily plastic. Conclusion SShD in the Drosophila wing can evolve rapidly and therefore shows only weak phylogenetic structure. The variable contribution of allometric and non-allometric components to the evolutionary divergence of SShD and the evolutionary plasticity of allometry suggest that SShD and allometry are influenced by a complex interaction of processes.
Turkish Journal of Entomology, 2018
Literature concerning phenotypic variation among wild-caught drosophilids inhabiting varied ecological habitats is relatively rare. The present study explores pattern of body size traits along altitudinal gradients, and compensation to colder environments and reduced air pressure via adjustment of wing morphology at higher altitudes. Wild adult flies were collected in two extensive surveys during September-October 2014 and April-May 2015. All traits were measured for both the sexes to obtain data on sexual dimorphism. It was found that though these populations differed significantly in their size, as already known, they deviated from the expected reaction norms of size increase along altitudinal gradients as observed in several previous studies. This deviation from normal clinal trend can be attributed to variation in growth rates and development times at different altitudes which has important implications in overall reproductive success. Also, a significant increase in wing area of flies at higher altitude was recorded with dramatically lower wing loadings than flies that developed in comparatively warmer habitats, giving them an aerodynamic advantage at cold temperatures. Thorax width was also analyzed, possibly for the first time in wild-caught flies of Indian populations, revealing sexual dimorphism. The ratio of thorax length to width was greater than one for all species indicating that the thorax is more elongated in females, which may also influence the flight capacity of the sexes.
Genetica, 1999
Traditional morphometrics' allows us to decompose morphological variation into its major independent sources, identifying them usually as size and shape. To compare and investigate the properties of size and shape in natural populations of Drosophila mediopunctata, estimating their heritabilities and analysing their temporal and microgeographic changes, we carried out collections on seven occasions in Parque Nacional do Itatiaia, Brazil. In one of these collections, we took samples from five different altitudes. Measurements were taken from wild caught inseminated females and up to three of their laboratory-reared daughters. Through a principal component analysis, three major sources of variation were identified as due to size (the first one) and shape (the remaining two). The overall amount of variation among laboratory flies was about half of that observed among wild flies and this reduction was primarily due to size. Shape variation was about the same under natural and artificial conditions. A genetic altitudinal cline was detected for size and shape, although altitude explained only a small part of their variation. Differences among collections were detected both for size and shape in wild and laboratory flies, but no simple pattern emerged. Shape variation had high heritability in nature, close to or above 40% and did not vary significantly temporally. Although on the overall size heritability (18 ± 6%) was significant its estimates were not consistent along months-they were non-significant in all but one month, when it reached a value of 51 ± 11%. Overall, this suggests that size and shape have different genetic properties.
Heredity, 2004
The fruit-flies Drosophila paranaensis and Drosophila mercatorum pararepleta are sibling species belonging to the repleta group. Females of these two species are normally considered to be morphologically indistinguishable while males only differ consistently in the morphology of their genitalia. These species are sympatric throughout a large area of their geographic distribution. In this study, we investigated the degree of morphological divergence between D. paranaensis and D. mercatorum pararepleta based on morphometric analysis of their wings. The ellipse method was used to describe the placement of the longitudinal and transversal wing veins as well as the size of the wing and the shape of its outline. The heritability under laboratory and field conditions was also estimated from the parameters generated. Multivariate analysis showed that wing morphology possessed sufficient differences to discriminate between the two species with a successful classification rate of 95-98% for females and 82-87% for males. The results of the autoclassification were confirmed by a cross-validation test for females (92-96%). Most measurements possessed significant natural heritability (a mean of 0.48 for D. mercatorum and 0.88 for D. paranaensis), indicating that the variation observed was related to differences in genes acting additively. The principal difference between the two species was in the placement of the posterior transverse wing vein. However, the pattern of morphological variation in the wings of both species was similar, possibly because of shared restrictions in wing development pathways.
Correlates of sexual dimorphism for dry weight and development time in five species of Drosophila
Journal of Zoology, 2004
Pre-adult development time, dry weight at eclosion, and daily fecundity over the first 10 days of adult life were measured in five species of Drosophila from the melanogaster and immigrans species groups. Overall, the three species of the melanogaster group (D. melanogaster, D. ananassae, D. malerkotliana) developed faster, were lighter at eclosion, and produced more eggs per unit weight at eclosion than the two species of the immigrans group (D. n. nasuta, D. sulfurigaster neonasuta). The degree of sexual dimorphism in dry weight was greater than that in development time, but did not vary significantly among species, and was not correlated with fecundity, contrary to expectations that sexual selection for increased fecundity drives sexual size dimorphism in Drosophila. The degree of dimorphism in development time was significantly correlated with dry weight and fecundity, with lighter species tending to be more dimorphic for development time as well as more fecund, both in absolute terms and in terms of fecundity per unit weight. The results suggest that our understanding of the evolutionary forces maintaining sexual size dimorphism in Drosophila will probably benefit from more detailed studies on the correlates of sexual dimorphism within and among Drosophila species, and on the shape of reaction norms for the degree of sexual dimorphism across different levels of ecologically relevant environmental variables.
1986
Sexual dimorphism in genetic parameters is examined for wing dimensions of Drosophila melanogaster. Data are fit to a quantitative genetic model where phenotypic variance is a linear function of additive genetic autosomal variance (common to both sexes), additive genetic X-linked variances distinct for each sex, variance due to common rearing environment of families, residual environmental variance, random error variance due to replication, and variance due to measurement error and developmental asymmetry (left us. right sides). Polygenic dosage compensation and its effect on genetic variances and covariances between sexes is discussed. Variance estimates for wing length and other wing dimensions highly correlated with length support the hypothesis that the Drosophila system of dosage compensation will cause male X-linked genetic variance to be substantially larger than female X-linked variance. Results for various wing dimensions differ, suggesting that the level of dosage compensation may differ for different traits. Genetic correlations between sexes for the same trait are presented. Total additive genetic correlations are near unity for most wing traits; this indicates that selection in the same direction in both sexes would have a minor effect on changing the magnitude of difference between sexes. Additive X-linked correlations suggest some genotype X sex interactions for X-linked effects.
A study of the genetic basis of the sexual dimorphism for wing length in Drosophila melanogaster
Genetics, 1972
The genetic basis of a sexually dimorphic quantitative character in Drosophila melanogaster was investigated by means of two-way directional selection for increased and decreased differences between male and female wing length. The sex dimorphism (SD), defined as the mean wing length difference between the sexes, within families, provided the criterion for selection.-The two lines (High SD, Low SD) diverged rapidly during the 15 generations of selection, indicating the presence of extensive genetic variability for the genotype-sex interaction underlying the observed sexual dimorphism. There was evidence that genetic variability persisted in both lines when selection was relaxed. Most of the divergence between the two lines remained after 10 generations of relaxed selection.-The change in the level of sex dimorphism in the High line was due primarily to a decrease in male wing length; in the Low line most of the change in SD was the result of a decrease in female wing length. An over...
Developmental constraints and wing shape variation in natural populations of Drosophila melanogaster
Heredity, 1997
The body sizes and shapes of poikilothermic animals generally show clinal variation with latitude. Among the environmental factors responsible for the dine, temperature seems to be the most probable candidate. In the present work we analysed natural populations of Drosophila melanogaster collected at different geographical localities to determine whether the same selective forces acting on wing development in the laboratory are also at work in the wild. We show that the temperature selection acting on wing development in the laboratory is only one of the selective forces operating in the wild. The size differences between natural populations seem to depend exclusively on cell number whereas they depend on cell area in the laboratory. The two wing compartments behave as distinct units of selection subjected to different genetic control, confirming our previous observations on laboratory populations. In addition, subunits of development defined as regions of cell proliferation centres restricted within longitudinal veins can, in turn, be considered as subunits of selection. Their interaction during development and continuous natural selection around an optimum could explain the high wing shape stability generally found in natural populations.