Spatial differences in patterns of modification: selection on hairy in Drosophila melanogaster wings

Artificial selection was carried out for over 45 generations to enhance and suppress expression of the mutation hairy on the Drosophila melanogaster w ing. Whole chromosome mapping of X-linked and autosomal modifiers of sense organ number displayed regional differences in magnitude and direction of t heir effects. Regional specificity of modifier effects was also seen in som e interchromosomal interactions. Scanning electron microscopy allowed preci se measurement of sense organ size and position along the L3 longitudinal w ing vein. Sense organ size varied in a predictable fashion along the proxim al-distal axis, and the dorsal pattern differed from the ventral pattern. T he high and low selection lines differed most in the proximal portion of th e L3 vein. Extra sense organs in the High line were often associated with v ein fragments at locations predicted from ancestral vein patterns. Thus, re gional specificity of polygenic or quantitative trait locus modifier effect s was identified in several different parts of the wing.