Parkash R, Sharma V, Kalra B. Climatic adaptations of body melanisation in Drosophila melanogaster from Western Himalayas. Fly

Department of Biochemistry and Genetics, Maharshi Dayanand University, Rohtak, India.
Fly (Impact Factor: 3.33). 06/2008; 2(3):111-7. DOI: 10.4161/fly.6351
Source: PubMed


We investigated population divergence in body melanisation in wild samples of Drosophila melanogaster across an elevational gradient (512-2202 m) in the Western Himalayas. Wild populations are characterized by higher phenotypic variability as compared with laboratory populations. Significant differences in elevational slope values for three posterior abdominal segments (fifth, sixth and seventh) in wild versus laboratory populations suggest plastic effects. However, elevational slope values do not differ for the three anterior abdominal segments (second, third and fourth). Thus, elevational changes in melanisation include genetic as well as plastic effects. Fitness consequences of within population variability were analyzed on the basis of assorted darker and lighter flies from two highlands as well as from two lowland localities. There is lack of correlation of melanisation with body size as well as ovariole number in assorted darker and lighter flies. For each population, darker flies showed higher desiccation resistance, lower rate of water loss, longer copulation duration and greater fecundity as compared with lighter flies. Phenotypic variations in body melanisation can be interpreted in relation with seasonal changes in temperature as well as humidity (Tcv and RHcv) of the sites of origin of populations. Thus, elevational changes in body melanisation may represent genetic response to selection pressures imposed by colder and drier climatic conditions in the Western Himalayas.

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Available from: Bhawna Kalra
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    • "This is facilitated by tools available in model organisms, including D. melanogaster, which allow the expression of specific genes to be modified, and effects of polymorphisms to be assessed in controlled backgrounds. A combination of approaches has allowed the adaptive significance of particular genetic changes to be identified: for instance, expression of the ebony gene affects body pigmentation (Pool and Aquadro, 2007; Telonis- Scott et al., 2011), which in turn may influence fitness under different climatic conditions (Parkash et al., 2008) and shows clinal patterns (Telonis-Scott et al., 2011); a set of polymorphisms in the regulatory region influences expression of this gene (Takahashi and Takano-Shimizu, 2011). The genus Drosophila itself and related genera contain an enormous range of species adapted to different climatic regions. "

    Full-text · Article · Jan 2015 · Frontiers in Marine Science
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    • "Furthermore, lower rates of water loss in non-melanic and fixed-melanic species (9– 18 lg h À1 ) account for 30-h higher desiccation resistance as compared to melanic species (25–54 lg h À1 ). Moreover , in non-melanic Z. indianus and fixed-melanic D. busckii, a substantial level of between-population variation in the amount of cuticular lipid was observed (Parkash et al., 2008a, 2011). In the present study, aside from geographical divergence within species, these results were compared at interspecific level. "
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    ABSTRACT: The role of melanization and cuticular lipids in water conservation has been studied in many Drosophila species (Diptera: Drosophilidae). Nevertheless, a comparative approach to larval and adult stages of ecologically diverse, wild Drosophila species is still required. Based upon abdominal cuticular melanization patterns, wild-caught Drosophila species were categorized as (1) melanic, (2) fixed-melanic, or (3) non-melanic. At the interspecific level, the ecological significance of melanization and cuticular lipids was determined by the inverse association of melanization and cuticular water loss in melanic species, and of cuticular lipids and cuticular water loss in fixed-melanic and non-melanic species. Interestingly, higher amounts of cuticular lipids were also evident in fixed as well as non-melanic species, as compared to melanic species at larval stages, which is consistent with their differences in reduced water loss rates. Moreover, fixed-melanic and non-melanic species exhibited comparatively higher (ca. 1.8–2.0 fold) desiccation resistance. Thus, cuticular lipids provide a better waterproofing mechanism than melanization. Furthermore, acclimation to dehydration stress in adults improved desiccation resistance in melanic species, whereas such effects were lacking in fixed-melanic and non-melanic species. However, there were no changes in cuticular components as a consequence of desiccation acclimation. Thus, our results indicate that melanic, fixed-melanic, and non-melanic Drosophila species differ in the evolved physiological mechanisms of water conservation to adapt to dry conditions.
    Full-text · Article · Feb 2014 · Entomologia Experimentalis et Applicata
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    • "Individuals of several species have been shown to be darker when reared at lower temperatures (for example, butterflies and hoverflies: Marriott & Holloway, 1998). While geographic variation in melanism and body size has been studied separately, they have rarely been considered together, even though many authors invoke a thermal explanation for the observed patterns (but see Guppy, 1986; Parkash et al., 2008, 2010). To determine whether intraspecific body size clines in ectotherms reflect local adaptations to thermal conditions (Mayr, 1956; Endler, 1977; Gardner et al., 2009), we need to consider not only body size, but colour as well, because together they influence the thermal conditions experienced by an organism. "
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    ABSTRACT: Aim We explore geographic variation in body size within the wingless grasshopper, Phaulacridium vittatum, along a latitudinal gradient, and ask whether melanism can help explain the existence of clinal variation. We test the hypotheses that both male and female grasshoppers will be larger and lighter in colour at lower latitudes, and that reflectance and size will be positively correlated, as predicted by biophysical theory. We then test the hypothesis that variability in size and reflectance is thermally driven, by assessing correlations with temperature and other climatic variables. Location Sixty-one populations were sampled along the east coast of Australia between latitudes 27.63° S and 43.10° S, at elevations ranging from 10 to 2000 m a.s.l. Methods Average reflectance was used as a measure of melanism and femur length as an index of body size for 198 adult grasshoppers. Climate variables were generated by BIOCLIM for each collection locality. Hierarchical partitioning was used to identify those variables with the most independent influence on grasshopper size and reflectance. Results Overall, there was no simple relationship between size and latitude in P. vittatum. Female body size decreased significantly with latitude, while male body size was largest at intermediate latitudes. Rainfall was the most important climatic variable associated with body size of both males and females. Female body size was also associated with radiation seasonality and male body size with reflectance. The reflectance of females was not correlated with latitude or body size, while male reflectance was significantly higher at intermediate latitudes and positively correlated with body size. Analyses of climate variables showed no significant association with male reflectance, while female reflectance was significantly related to the mean temperature of the driest quarter. Main conclusions Geographic variation in the body size of the wingless grasshopper is best explained in terms of rainfall and radiation seasonality, rather than temperature. However, melanism is also a significant influence on body size in male grasshoppers, suggesting that thermal fitness does play a role in determining adaptive responses to local conditions in this sex.
    Full-text · Article · Aug 2012 · Journal of Biogeography
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