Molecular Basis of Adaptive Shift in Body Size in Drosophila melanogaster: Functional and Sequence Analyses of the Dca Gene

Abstract

Latitudinal body size clines in animals conforming to Bergmann's rule occur on many continents but isolating their underlying genetic basis remains a challenge. In Drosophila melanogaster, the gene Dca accounts for approximately 5-10% of the natural wing size variation (McKechnie SW, Blacket MJ, Song SV, Rako L, Carroll X, Johnson TK, Jensen LT, Lee SF, Wee CW, Hoffmann AA. 2010. A clinally varying promoter polymorphism associated with adaptive variation in wing size in Drosophila. Mol Ecol. 19:775-784). We present here functional evidence that Dca is a negative regulator of wing size. A significant negative latitudinal cline of Dca gene expression was detected in synchronized third instar larvae. In addition, we clarified the evolutionary history of the three most common Dca promoter alleles (Dca237-1, Dca237-2, and Dca247) and showed that the insertion allele (Dca247), whose frequency increases with latitude, is associated with larger wing centroid size and higher average cell number in male flies. Finally, we showed that the overall linkage disequilibrium (LD) was low in the Dca promoter and that the insertion/deletion polymorphism that defines the Dca alleles was in strong LD with two other upstream sites. Our results provide strong support that Dca is a candidate for climatic adaptation in D. melanogaster.

Polymorphism in the neurofibromin gene, Nf1, is associated with antagonistic selection on wing size and development time in Drosophila melanogaster

“…The In(3R)Payne variation was previously scored in the same 2005 field collection (McKechnie et al . ) using a SNP‐based PCR assay (Anderson et al . ).…”

Revisiting classic clines in Drosophila melanogaster in the age of genomics

“…High-latitude populations of D. melanogaster in Australia also have greater cold tolerance, but lower heat tolerance, than their lower latitude conspecifics [10,28]. In contrast to the North American cline, the incidence of diapause expression [29] and the number of ovarioles [26] display nonlinear associations with latitude in eastern Australia, which illustrates the fact that not all differentiation occurs in parallel among continents. Finally, recent work has shown a strong cline for the length of time that flies sleep: high-latitude populations of D. melanogaster in North America sleep for smaller bouts of time, and this pattern is reflected in higher nighttime locomotor activity in these populations [11].…”

ALTITUDINAL CLINAL VARIATION IN WING SIZE AND SHAPE IN AFRICANDROSOPHILA MELANOGASTER: ONE CLINE OR MANY?

“…Patterns of ecological variation like these have been exploited by investigators working on the genetic and molecular basis of adaptive changes in these traits: such as the genetics of body size clines (A. Gilchrist & Partridge 1999; Paaby et al 2010; McKechnie et al 2010; Lee et al 2011) and temperature-related variation in the regulation of heat shock protein expression (Sorensen et al 2001). Furthermore, pairs of potentially parallel clines can be compared in order to address the issues of contingency/repeatability in phenotypic evolution (e.g.…”