Data from: The large X-effect on secondary sexual characters and the genetics of variation in sex comb tooth number in Drosophila subobscura
Mittleman, Briana E., Duke University
Manzano-Winkler, Brenda, Duke University
Hall, Julianne B., Duke University
Korunes, Katharine L., Duke University
Noor, Mohamed A. F., Duke University
Published Nov 11, 2017 on Dryad.
Cite this dataset
Mittleman, Briana E. et al. (2017). Data from: The large X-effect on secondary sexual characters and the genetics of variation in sex comb tooth number in Drosophila subobscura [Dataset]. Dryad. https://doi.org/10.5061/dryad.sc833
Genetic studies of secondary sexual traits provide insights into whether and how selection drove their divergence among populations, and these studies often focus on the fraction of variation attributable to genes on the X-chromosome. However, such studies may sometimes misinterpret the amount of variation attributable to the X-chromosome if using only simple reciprocal F1 crosses, or they may presume sexual selection has affected the observed phenotypic variation. We examined the genetics of a secondary sexual trait, male sex comb size, in Drosophila subobscura. This species bears unusually large sex combs for its species group, and therefore, this trait may be a good candidate for having been affected by natural or sexual selection. We observed significant heritable variation in number of teeth of the distal sex comb across strains. While reciprocal F1 crosses seemed to implicate a disproportionate X-chromosome effect, further examination in the F2 progeny showed that transgressive autosomal effects inflated the estimate of variation associated with the X-chromosome in the F1. Instead, the X-chromosome appears to confer the smallest contribution of all major chromosomes to the observed phenotypic variation. Further, we failed to detect effects on copulation latency or duration associated with the observed phenotypic variation. Overall, this study presents an examination of the genetics underlying segregating phenotypic variation within species and illustrates two common pitfalls associated with some past studies of the genetic basis of secondary sexual traits.
R code used for QTL mapping sex comb variation and QTL effect size estimates
Strain Variation Data
Average of distal & proximal sex comb size for individual males from 5 lines of D. subobscura
X-chromosome mapping file
rQTL-formatted data file with male genotypes from 13 loci along X-chromosome. Relative map locations also listed in row 3. Individual proximal or distal sex combs measured as prox1, distal1, prox2, distal2, and then average sex comb size (when one sex comb was lost, the remaining assumed to be average). Plate, row, and column depict location in 96-well plates, and cytoplasm indicates grandmother strain (used to test for maternal effects).
Mapping data file
rQTL-formatted data file as above but with single marker genotypes from each chromosome.
Courtship/ mating experiments data
Data include time prior to copulation (TimePreCop) and duration of copulation (TimeCop). Distal sex comb sizes given as "Bigger" and "Smaller", and the average is given as well as the difference. The file also indicates if the flies mated as well as notes. Notes like "D2=7+2" mean one distal sex comb was "broken" into two segments with 7 and 2 teeth respectively.