Stress temperatures and quantitative variation in Drosophila melanogaster

Abstract

Using an isofemale line analysis, we analysed the consequences of extreme rearing temperatures for genetic variation in quantitative characters in Drosophila melanogaster. Three types of characters were used: life history (viability and developmental time), body size (thorax length and wing length) and meristic (number of sternopleural chaetae and number of arista branches). Phenotypic variation significantly increased under stress conditions in all morphological characters studied; for viability, it increased at the low stress temperature. Genetic variation, measured by the coefficient of intraclass correlation, was generally higher at both low and high stress temperatures for thorax length and sternopleural chaeta number. For wing length and viability, genetic variation was higher at the low extreme temperature. No consistent trend was found for genetic variation in arista branch number and developmental time. Our results agree with the hypothesis that genetic variation is increased in stressful environments. A possible mechanism underlying this phenomenon is briefly discussed.

Variation in morphological traits of Drosophila melanogaster (fruit fly) under nutritional stress

“…In a similar manner, fluctuating asymmetry of all bilateral traits studied increased significantly, which indicated an increase in the amount of 'developmental noise' under this type of stress. These results are not unexpected as, in our previous work, in which the effect of rearing D. melanogaster at extreme temperatures on essentially the same set of morphological traits was examined, the temperature stress consistently resulted in a significant increase in phenotypical variation and FA (Imasheva et al, 1997(Imasheva et al, , 1998.…”

“…They concluded that genetic variation for body size traits in these species was generally higher when reared at less favourable temperatures. In D. melanogaster, temperature extremes (12°C and 31°C) have been shown to increase both additive genetic variance and isofemale heritabilities for thorax length, sternopleural chaeta number (both extreme temperatures) and wing length (low temperature) (Imasheva et al, 1998). In contrast to these results, Sgrò & Hoffmann [cited in Jenkins et al (1997)], comparing genetic variance of wing length in parents and their firstgeneration offspring subjected to the same or different temperatures, did not find any effect of temperature extremes on the expression of genetic variation in D. melanogaster.…”

“…The aim of the present study was to assess the effect of nutritional stress on the expression of phenotypical and genetic variation of morphological traits in Drosophila melanogaster and to compare it with the effects of another type of stress, exposure to extreme temperatures, which was studied previously (Imasheva et al, 1997(Imasheva et al, , 1998. To estimate additive genetic variation, the coefficient of intraclass correlation was used as a measure of heritability (Hoffmann & Parsons, 1988) and evolvability (Houle, 1992) of the traits.…”

Effect of low stressful temperature on genetic variation of five quantitative traits in Drosophila melanogaster

“…Quantitative variation in different environments has been extensively studied in the last decade using Drosophila (eg, Gebhardt and Stearns, 1992;David et al, 1994;Barker and Krebs, 1995;Hoffmann and Schiffer, 1998;Imasheva et al, 1998;Loeschcke et al, 1999;. The results of these studies indicated the possibility of both higher and of lower additive genetic variances/heritabilities under stress as well as the absence of changes across environments.…”

“…The data suggest that the effect of stressful temperature may be trait-specific and this warns against generalizations about the behaviour of genetic variation under extreme conditions. Heredity (2002) 89, 70-75. doi:10.1038/sj.hdy.6800104 Imasheva et al, 1998Imasheva et al, , 1999Imasheva et al, , 2000Karan et al, 1999;Loeschcke et al, 1999) in which genetic parameters have been estimated using the isofemale line technique, ie, a modified full-sib design with isofemale lines treated as families (Hoffmann and Parsons, 1988). However, the full-sib design is the least precise among all quantitative genetics methods developed to estimate additive genetic variance.…”