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1 January 2001 SEX-LINKED EXPRESSION OF A SEXUALLY SELECTED TRAIT IN THE STALK-EYED FLY, CYRTODIOPSIS DALMANNI
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Abstract

Recent theoretical and empirical work has suggested that the X chromosome may play a special role in the evolution of sexually dimorphic traits. We tested this idea by quantifying sex chromosome influence on male relative eyespan, a dramatically sexually selected trait in the stalk-eyed fly, Cyrtodiopsis dalmanni. After 31 generations of artificial sexual selection on eyespan:body length ratio, we reciprocally crossed high- with low-line flies and found no evidence for maternal effects; the relative eyespan of F1 females from high- and low-line dams did not differ. However, F1 male progeny from high-line dams had longer relative eyespan than male progeny from low-line dams, indicating X-linkage. Comparison of progeny from a backcross involving reciprocal F1 males and control line females confirmed X-linked inheritance and indicated no effect of the Y chromosome on relative eyespan. We estimated that the X chromosome accounts for 25% (SE = 6%) of the change in selected lines, using the average difference between reciprocal F1 males divided by the difference between parental males, or 34%, using estimates of the number of effective factors obtained from reciprocal crosses between a high and low line. These estimates exceed the relative size of the X in the diploid genome of a male, 11.9% (SE = 0.3%), as measured from mitotic chromosome lengths. However, they match expectations if X-linked genes in males exhibit dosage compensation by twofold hyperactivation, as has been observed in other flies. Therefore, sex-linked expression of relative eyespan is likely to be commensurate with the size of the X chromosome in this dramatically dimorphic species.

Corresponding Editor: K. Ross

L. LaReesa Wolfenbarger and Gerald S. Wilkinson "SEX-LINKED EXPRESSION OF A SEXUALLY SELECTED TRAIT IN THE STALK-EYED FLY, CYRTODIOPSIS DALMANNI," Evolution 55(1), 103-110, (1 January 2001). https://doi.org/10.1554/0014-3820(2001)055[0103:SLEOAS]2.0.CO;2
Received: 24 March 2000; Accepted: 1 August 2000; Published: 1 January 2001
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