A Quantitative Genetic Analysis of Male Sexual Traits Distinguishing the Sibling Species Drosophila simulans and D. sechellia

Abstract A quantitative trait locus (QTL) genetic analysis of morphological and reproductive traits distinguishing the sibling species Drosophila simulans and D. sechellia was carried out in a backcross design, using 38 markers with an average spacing of 8.4 cM. The direction of QTL effects for the size of the posterior lobe was consistent across the identified QTL, indicating directional selection for this trait. Directional selection also appears to have acted on testis length, indicating that sexual selection may have influenced many reproductive traits, although other forms of directional selection cannot be ruled out. Sex comb tooth number exhibited high levels of variation both within and among isofemale lines and showed no evidence for directional selection and, therefore, may not have been involved in the early speciation process. A database search for genes associated with significant QTL revealed a set of candidate loci for posterior lobe shape and size, sex comb tooth number, testis length, tibia length, and hybrid male fertility. In particular, decapentaplegic (dpp), a gene known to influence the genital arch, was found to be associated with the largest LOD peak for posterior lobe shape and size.

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Genetic architecture of variation in sex-comb tooth number in Drosophila simulans

Genetics Research ◽

10.1017/s0016672306008111 ◽

2006 ◽

Vol 87 (2) ◽

pp. 93-107 ◽

Cited By ~ 11

Author(s):

HARUKI TATSUTA ◽

TOSHIYUKI TAKANO-SHIMIZU

Keyword(s):

Interspecific Variation ◽

Drosophila Simulans ◽

Epistatic Interactions ◽

The Third ◽

Sex Comb ◽

Tooth Number ◽

Comb Tooth ◽

Trait Locus ◽

The Relationship ◽

Mapping Populations

The sex comb on the forelegs of Drosophila males is a secondary sexual trait, and the number of teeth on these combs varies greatly within and between species. To understand the relationship between the intra- and interspecific variation, we performed quantitative trait locus (QTL) analyses of the intraspecific variation in sex-comb tooth number. We used five mapping populations derived from two inbred Drosophila simulans strains that were divergent in the number of sex-comb teeth. Although no QTLs were detected on the X chromosome, we identified four QTLs on the second chromosome and three QTLs on the third chromosome. While identification and estimated effects of the second-chromosome QTLs depend on genetic backgrounds, significant and consistent effects of the two third-chromosome QTLs were found in two genetic backgrounds. There were significant epistatic interactions between a second-chromosome QTL and a third-chromosome QTL, as well as between two second-chromosome QTLs. The third-chromosome QTLs are concordant with the locations of the QTLs responsible for the previously observed differences in sex-comb tooth number between D. simulans and D. mauritiana.

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Genetics of sexual isolation in male hybrids of Drosophila simulans and D. mauritiana

Genetics Research ◽

10.1017/s0016672300034182 ◽

1996 ◽

Vol 68 (3) ◽

pp. 211-220 ◽

Cited By ~ 23

Author(s):

Jerry A. Coyne

Keyword(s):

Genetic Analysis ◽

Y Chromosome ◽

Sibling Species ◽

Previous Analysis ◽

Sexual Isolation ◽

Drosophila Simulans

SummarySexual isolation between the sibling species D. simulans and D. mauritiana is due largely to the rejection of D. simulans males by D. mauritiana females. Genetic analysis shows that genes on the X and third chromosomes contribute to the differences between males causing sexual isolation, while the Y chromosome, second chromosome and cytoplasm have no effect. These chromosome effects differ from those observed in a previous analysis of sexual isolation in hybrid females, implying that different genes cause sexual isolation in the two sexes.

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