Sex-linked expression of a sexually selected trait in the stalk-eyed fly, Cyrtodiopsis dalmanni

L. Lareesa Wolfenbarger, Gerald S. Wilkinson

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36 Scopus citations

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.

Original languageEnglish (US)
Pages (from-to)103-110
Number of pages8
JournalEvolution
Volume55
Issue number1
DOIs
StatePublished - Jan 1 2001

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Keywords

  • Artificial selection
  • Diopsidae
  • Dosage compensation
  • Sexual dimorphism
  • X-linkage

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics
  • Agricultural and Biological Sciences(all)

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