Genetic variation and plasticity of thorax length and wing length in Drosophila aldrichi and D. buzzatii

Abstract

Reaction norms across three temperatures of development were measured for thorax length, wing length and wing length/thorax length ratio for ten isofemale lines from each of two populations of Drosophila aldrichi and D. huzzatii. Means for thorax and wing length in both species were larger at 24 "C than at either 18 "C or 31 "C, with the reduction in size at 18 "C most likely due to a nutritional constraint. Although females were larger than males, the sexes were not different for wing length/thorax length ratio. The plasticity of the traits differed between species and between populations of each species, with genetic variation in plasticity similar for the two species from one locality, but much higher for D. aldrichi from the other. Estimates of heritabilities for D. aldrichi generally were higher at 18 'C and 24 "C than at 31 "C, but for D. huzatii they were highest at 31 "C, although heritabilities were not significantly different between species at any temperature. Additive genetic variances for D. aldrichi showed trends similar to that for heritability, being highest at 18 "C and decreasing as temperature increased. For D. huzzatii, however, additive genetic variances were lowest at 24 "C. These results are suggestive that genetic variation for body size characters is increased in more stressful environments. Thorax and wing lengths showed significant genetic correlations that were not different between the species, but the genetic correlations between each of these traits and their ratio were significantly different. For D. aldrichi, genetic variation in the wing length/thorax length ratio was due primarily to variation in thorax length, while for D. huszatii, it was due primarily to variation

Stress temperatures and quantitative variation in Drosophila melanogaster

“…thorax length and wing length. As it has been repeatedly reported by several authors (David et al, 1994;Barker & Krebs, 1995;Lazebny et al, 1996; the present work), this effect can be considered as established. We also recorded the same effect for another morphological character, sternopleural chaeta number, although in this case it was less marked.…”

“…David et al (1994) reported a slight increase of the coefficient of intraclass correlation of wing length and thorax length in D. melanogaster reared at 12°C and 31°C compared to that at intermediate temperatures. Barker & Krebs (1995) examined the effect of temperature of development on genetic variation in wing length, thorax length, and the wing/thorax ratio in D. aldrichi and D. buzzatii. In both species, heritabilities for the body size characters were higher in stressful environments; in D. aldrichi, the additive genetic variance also increased at the extreme temperatures.…”

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 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. Most evidence for increased additive variation has been obtained in experiments (Barker and Krebs, 1995;de Moed et al, 1997; Correspondence: OA Bubliy, Vavilov Institute of General Genetics, Gubkin Street 3, 119991 Moscow, Russia. E-mail: olegFb@vigg whereas thorax length did not show any trend.…”

Phenotypic plasticity in colonizing populations of Drosophila subobscura

“…Powell (1974) suggested that some populations show genetic variation for body size for reasons other than temperature adaptations and it is only in the artificial, laboratory environment that temperature is the selective force on this variance. On the other hand, phenotypic variance has been shown to increase in stressful environments (Burla and Taylor, 1982;Barker and Krebs, 1995), suggesting that this phenomenon could contribute to the increase observed in genetic variation in marginal environments, with more rapid evolution during periods of special stress.…”