The genetic architecture of coordinately evolving male wing pigmentation and courtship behavior in Drosophila elegans and Drosophila gunungcola.
Bottom Line: On the autosomes, QTL locations for pigmentation and behavior were generally separate, but on the X chromosome two clusters of QTL were found affecting both wing pigmentation and courtship behavior.Pairwise tests for interactions between marker loci revealed evidence of epistasis between putative QTL for wing pigmentation but not those for courtship behavior.The clustering of X-linked QTL for male pigmentation and behavior is consistent with the concerted evolution of these traits and motivates fine-scale mapping studies to elucidate the nature of the contributing genetic factors in these intervals.
Affiliation: Department of Ecology and Evolution, Stony Brook University, Stony Brook, New York 11794-5245.Show MeSH
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Mentions: Our results suggest that for wing spots, epistatic interactions may be involved in determining the effects of divergent QTL loci on the phenotype. Two different types of gene functions could be envisioned as part of such a mechanism. One type of locus, a “regulator,” would determine whether pigment could be deposited in the wing spot area, the other type, a “modifier,” would control the intensity (including the darkness and size) of pigmentation in the wing spot area (Figure 5A). Given such a functional division, the loss of wing spots in the D. gunungcola lineage could occur by two different scenarios: “regulators first” or “modifiers first.” In the “regulators first” scenario, changes of upstream regulators might occur first to knock out the expression of melanin pathway genes in the wing spot area. Mutations in wing-spot-specific regulatory regions of modifiers would subsequently accumulate over time, due to the relaxation of selective pressure or genetic drift (Figure 5B). Alternatively, in the “modifiers first” scenario, loss of modifier gene expression in the wing spot region might have occurred and been fixed in the population before the changes of regulators (Figure 5C). In the former scenario, the pigmentation in wing spot area would disappear before the fixation of any changes in downstream pigmentation genes. In the later scenario, the pigmentation intensity might have been lost gradually with or without later changes in regulator genes.
Affiliation: Department of Ecology and Evolution, Stony Brook University, Stony Brook, New York 11794-5245.