Phenotypic plasticity of sternopleural bristle number in temperate and tropical populations of Drosophila melanogaster.
We investigated the phenotypic plasticity of sternopleural bristle (SB) number as a function of growth temperature in isofemale lines from temperate (France) and tropical (Congo) populations of Drosophila melanogaster. We found concave reaction norms with a maximum in the middle of the thermal range, except in four African lines which exhibited a regularly decreasing response curve. Genetic variability (intraclass correlation) and evolvability (genetic CV, coefficient of variation) were independent properties and did not change with temperature. Residual, within-line variability was, however, strongly influenced by growth temperature, showing a U-shaped response curve and a minimum CV of 9% at 21.5 degrees C. As expected from a previously known latitudinal cline, maximum values (MV) were higher in temperate than in tropical flies. The temperature of maximum value (TMV) was observed at a higher temperature in the tropical population, in agreement with similar adaptive trends already observed for other quantitative traits. Significant negative correlations within each population were observed between a plasticity curvature parameter and MV or TMV. No difference in curvature was, however, observed between populations, in spite of their very different MVs.
Moreteau
Brigitte
B
Laboratoire Populations, Génétique et Evolution, CNRS, 91 198 Gif sur Yvette Cedex, France. Brigitte.Moreteau@pge.cnrs-gif.fr
Gibert
Patricia
P
Delpuech
Jean-Marie
JM
Petavy
Georges
G
David
Jean R
JR
D000818:Animals; D004330:Drosophila / Q000235:genetics*; D005260:Female; D014644:Genetic Variation; D010641:Phenotype; D013045:Species Specificity