Genetic architecture of a morphological shape difference between two Drosophila species

• Published in: Genetics (Austin) 2000, Vol.154 (1), p.299-310
• Main Authors: Zeng, Z.B, Liu, J, Stam, L.F, Kao, C.H, Mercer, J.M, Laurie, C.C
• Format: Article
• Language: English
• Subjects: additive effect; anatomy and morphology; Animals; Base Sequence; chromosome mapping; composite interval mapping; DNA Primers; dominance; Drosophila; Drosophila - anatomy & histology; Drosophila - genetics; Drosophila mauritiana; Drosophila simulans; elliptical fourier analysis; epistasis; genetic effects; Genetics; Genotype; heritability; Insects; loci; Lod Score; male genitalia; multiple interval mapping; phenotypic variation; Polymerase Chain Reaction; posterior lobe of the male genital arch; principal component analysis; Quantitative Trait, Heritable; quantitative traits; Reproductive system; shape; size; Species Specificity; statistical analysis
• ISSN: 0016-6731; 1943-2631; 1943-2631
• DOI: 10.1093/genetics/154.1.299

The size and shape of the posterior lobe of the male genital arch differs dramatically between Drosophila simulans and D. mauritiana. This difference can be quantified with a morphometric descriptor (PC1) based on elliptical Fourier and principal components analyses. The genetic basis of the interspecific difference in PC1 was investigated by the application of quantitative trait locus (QTL) mapping procedures to segregating backcross populations. The parental difference (35 environmental standard deviations) and the heritability of PC1 in backcross populations (>90%) are both very large. The use of multiple interval mapping gives evidence for 19 different QTL. The greatest additive effect estimate accounts for 11. 4% of the parental difference but could represent multiple closely linked QTL. Dominance parameter estimates vary among loci from essentially no dominance to complete dominance, and mauritiana alleles tend to be dominant over simulans alleles. Epistasis appears to be relatively unimportant as a source of variation. All but one of the additive effect estimates have the same sign, which means that one species has nearly all plus alleles and the other nearly all minus alleles. This result is unexpected under many evolutionary scenarios and suggests a history of strong directional selection acting on the posterior lobe.