Dissecting adaptive clinal variation: markers, inversions and size/stress associations in Drosophila melanogaster from a central field population

Abstract

Many organisms show latitudinal variation for quantitative traits that is assumed to be due to climatic adaptation. These clines provide an opportunity to study the genetics of the adaptive process both at the phenotypic and the underlying molecular levels. Yet researchers rarely try to link variation in quantitative traits to their underlying molecular genetic basis. We describe a novel approach for exploring the genetic basis for clinal variation in size and stress traits in Drosophila melanogaster. We look for associations between genetic markers and traits that exhibit clinal patterns on the east coast of Australia using a single, geographically central population. There are strong associations between markers found within In(3R)Payne and variation in size, suggesting that this inversion explains much of the clinal variation in this trait. We also find that development time is associated with the Adh allozyme locus, cold resistance is negatively associated with the In(3L)Payne inversion and a genetic marker for Hsp70, a heat‐shock protein, is associated with heat resistance. Finally we discuss the importance of inversions in clinal variation for quantitative traits and for identifying quantitative trait loci.

Protein synthesis rates in Drosophila associate with levels of the hsr-omega nuclear transcript

“…The genetic variation of the natural population is therefore spread at random across lines and the effects of inbreeding and artificial linkage associations are minimised (Weeks et al 2002). Basal rates of protein synthesis showed a 2.1-fold level of variation across lines (Fig.…”

Latitudinal and cold-tolerance variation associate with DNA repeat-number variation in the hsr-omega RNA gene of Drosophila melanogaster

“…Using a set of single-pair-mating family lines derived by Weeks et al (2002), variation in hsr-omega repeats was examined for associations with three traits, cold tolerance (chill-coma recovery time), heat resistance (knockdown time) and wing size, traits that were characterized for these families three generations earlier (Weeks et al, 2002). Southern blots were carried out on DNA extracted from 25 adults from each family line which was scored for both the frequency of fr (few-repeat) alleles ( ¼ combined frequency of band groups containing bands o10.6 kb) and the frequency of mr (many-repeat) alleles ( ¼ combined frequency of groups containing bands 414.5 kb), determined by comparison to bands of standard sizes run on every gel.…”

“…This cross isolated independent chromosomes in separate fly lines. Within each line progeny that did not contain the balancer phenotype were used for scoring three markers on the right arm of chromosome three; hsr-omega-L/S, the closely linked microsatellite DMU25686, and In(3R)P. hsr-Omega-L/S and DMU25686 were genotyped using previously described methods (Gockel et al, 2001;Weeks et al, 2002). In(3R)P was scored by polytene chromosome squashes and confirmed by a PCR-product gel assay (Anderson et al, 2005b).…”

“…Various measures of heat resistance have been used in recent studies, some of which have found associations with hsr-omega-L/S variation and some of which have not (Weeks et al, 2002;Norry et al, 2004;Morgan and Mackay, 2006;Rako et al, 2007). One of the confounding factors in these association studies is the linkage disequilibrium of hsr-omega with breakpoints of the common cosmopolitan inversion In(3R)Payne (Kennington et al, 2006).…”

Genetic mapping of adaptive wing size variation in Drosophila simulans

“…However, the QTL on 3R also coincides with the cosmopolitan chromosomal inversion 3RP (In(3R)Payne), which shows a strong clinal pattern and accounts for 30-60% of the size variance (Weeks et al, 2002;Rako et al, 2006). The presence of this inversion polymorphism in mapping populations impedes fine-scale mapping.…”