X chromosome influences sperm length in the stalk-eyed fly Cyrtodiopsis dalmanni.
Whether sexually selected traits are sex linked can have profound effects on their evolution. In the diopsid stalk-eyed fly, Cyrtodiopsis dalmanni, sperm length and female reproductive tract morphology have coevolved across species, postcopulatory sexual selection is known to occur, and X-linked genes affect female ventral sperm receptacle size. Here, we estimate the location of quantitative trait loci (QTL) for spermatocyst tail length by using F2 progeny segregating for an X-linked factor that causes sex-ratio meiotic drive. We found two QTL, including a major X-linked QTL responsible for 25% of the variation in spermatocyst tail length 2.1 cM from the sex-ratio element and 0.8 cM from a major eye span QTL. Sex-ratio males produce shorter spermatocyst tails and shorter eye spans. Thus, X-linked factors affect both pre- and postcopulatory traits, and linkage between the alleles for short eye span and short spermatocyst tail length allow pre- and postcopulatory sexual selection to potentially act in concert against the transmission bias caused by the sex-ratio chromosome.
Johns
P M
PM
Department of Biology, University of Maryland, College Park, MD, USA. philipjohns1@yahoo.com
Wilkinson
G S
GS
D000818:Animals; D004175:Diptera / Q000166:cytology* / Q000235:genetics*; D008297:Male; D040641:Quantitative Trait Loci; D013094:Spermatozoa / Q000166:cytology*; D014960:X Chromosome / Q000235:genetics*