Impact of Darker, Intermediate and Lighter Phenotypes of Body Melanization on Desiccation Resistance inDrosophila melanogaster

Abstract

A possible link between melanization and desiccation resistance can be inferred if within population differences in melanization find significant correlations with desiccation resistance and its mechanistic basis i.e. rate of water loss/hr. Accordingly, darker, intermediate and lighter phenotypes of body melanization were analyzed in wild and laboratory reared Drosophila melanogaster L. (Diptera: Clyclorrapha) populations from highland and lowland sites located in close proximity at five different latitudinal locations (11.15 °N to 31.06°N) within the Indian subcontinent. In large population samples, occurrence of significant within population variability made it possible to assort non-overlapping phenotypes of body coloration (i.e. lighter (< 25%), intermediate (30 to 40%) and darker (> 45%)) for all the populations which were further investigated for desiccation resistance and rate of water loss/hr. Significantly, higher desiccation resistance but much reduced rate of water loss/hr were observed in darker and intermediate phenotypes in all the populations. By contrast, lighter phenotypes exhibited lower desiccation tolerance but higher rate of water loss/hr. A regression analysis between traits provided similar slope values for wild and laboratory populations. For all three physiological traits, predicted trait values from multiple regression analysis as a simultaneous function of annual average temperature and relative humidity, matched the observed values. We infer that parallel changes in melanization and desiccation resistance may result from decreasing annual average temperature and relative humidity along increasing latitude as well as altitude on the Indian subcontinent.

Water loss in tree weta (Hemideina): adaptation to the montane environment and a test of the melanisation–desiccation resistance hypothesis

“…Under this resistance hypothesis, melanic individuals have a selective advantage in more desiccating environments, like montane environments, than less or non-melanic individuals. Melanic Drosophila morphs were found in more-desiccating environments (higher altitudes) than non-melanic morphs (Parkash et al, 2008b(Parkash et al, , 2009, whereas darker abdominal pigmentation positively correlated strongly with altitude in sub-Saharan D. melanogaster populations (Pool and Aquadro, 2007). However, the altitudinal distribution of melanic H. maori differs from this pattern.…”

Pigmentation and behavior: potential association through pleiotropic genes in <i>Drosophila</i>

“…Regarding other environmental factors, a strong association of pigmentation intensity and desiccation resistance has been reported within and among D. melanogaster populations from India (Parkash et al, 2008a(Parkash et al, , 2008b(Parkash et al, , 2009, which suggests that humidity related adaptation may be important in some regions. However, a study on longitudinal cline of pigmentation variation in a different species, D. americana, did not find any association between pigmentation and desiccation resistance (Wittkopp et al, 2011;Clusella-Trullas and Terblanche, 2011).…”

“…The first report of the trident polymorphism from a natural population was by the pioneers of Drosophila geneticists, Morgan and Bridges (1919), followed by Jacobs (1960Jacobs ( , 1961, and David et al (1985). What is particularly noticeable about the studies on pigmentation variation within this species is that a clinal variation in pigmentation intensity is repeatedly observed along altitude or latitude or both (David et al, 1985;Munjal et al, 1997;Pool and Aquadro, 2007;Parkash et al, 2008aParkash et al, , 2008bParkash et al, , 2009Telonis-Scott et al, 2011). These observations of non-random distribution of the phenotype can be a circumstantial evidence that supports environmental adaptation playing a role in shaping the diverse patterns of body pigmentation.…”

Rapid desiccation hardening changes the cuticular hydrocarbon profile of Drosophila melanogaster

“…The majority of insect water loss is across the cuticle, due to the high surface area to volume ratio (Gibbs, 2002;Hadley, 1994), and reduced rates of cuticular water loss (CWL) are associated with greater resistance to desiccation (Parkash et al, 2008). Cuticular permeability can be modified via structural changes to the cuticle, such as melanisation (Hadley, 1978;Parkash et al, 2009aParkash et al, , 2009b, or through changes to the quantity and identity of cuticular hydrocarbons (CHCs) (Gibbs and Pomonis, 1995). It has been suggested that cuticular permeability can be reduced by increasing total amount, saturation, and chain length of CHCs (Gibbs and Pomonis, 1995).…”