HERITABLE VARIATION IN RESOURCE UTILIZATION AND RESPONSE IN A WINERY POPULATION OFDROSOPHILA MELANOGASTER

Abstract

Abstract. -It has been found that Drosophila melanogasterlines from the "Chateau Tahbilk" winery cellar had higher larval ethanol resistance than lines originating from outside the cellar. Because the adaptive significance of this trait is unclear, we have reexamined genetic microdifferentiation at Tahbilk with other resources and different tests for ethanol adaptation. Cellar stocks tended to be more resistant to starvation after exposure to wine seepage than stocks originating from orchard traps outside the cellar. Lines from a grape residue pile were also more resistant to starvation after seepage exposure than orchard stocks even though these collection sites were a few meters apart. Cellar and orchard stocks did not differ in ethanol resistance as measured by larval viability tests on low sucrose medium. However, stocks from the grape residue pile showed an increase in adult longevity over ethanol vapor compared to those from the cellar or orchard stocks. These differences were not due to maternal effects. In laboratory tests of behavioral responses, cellar stocks were relatively more attracted to seepage than orchard stocks in one year but not in the other two years. The findings suggest some adaptive differentiation related to resource heterogeneity at Tahbilk.

Micro-spatial population differentiation in activity of glycerol-3-phosphate oxidase (GPO) from mitochondria of Drosophila melanogaster

“…Although there is ample opportunity each year at vintage time for flies to move between the cellar and outside areas, and thus for gene exchange to occur, there is a significant period when little if any influx of outside flies occurs (McKenzie, 1975(McKenzie, , 1980. Several generations of breeding occurs in cellar seepage sites during this time and this may be part of the reason why heritable differences between these two populations occurs in other quantitative traits (McKenzie & McKechnie, 1978;Hoffmann & McKechnie, 1991). Similar spatial quantitative differentiation of gene frequencies and morphological traits have recently been reported from a French winery population in D. melanogaster (AlonsoMoraga et al, 1988).…”

“…The Tahbilk cellar sites of larval development are cooler than outside sites (McKechnie & McKenzie, 1981), contain lower levels of free sugars (Hoffmann & McKechnie, 1991) and are at low light intensity. Other differences must occur.…”

“…These low levels are common in breeding sites of seepage from vats of unfortified wine (Gibson ef al., 1981). Also, compared to strains from outside, cellar strains are relatively poor performers on 3% ethanol medium (Hoffmann & McKechnie, 1991) a level that is likely to be higher than in the average cellar seepage site. Finally, Tahbilk lines that are more tolerant in a 6% ethanol test tend to have higher larval GPO activity (McKechnie & Geer, 1986), as do the outside strains.…”

“…Females were collected in the cellar by aspiration from seepage sites and outside from box traps, and set up singly in vials. Offspring from at least 30 fieldcollected females were pooled to form each mass-bred line as described by Hoffmann and McKechnie (1991).…”

“…On the other hand strains originating from the orchard just outside the building are more likely to be derived from a transient population which bred in a non-winery environment. Quantitative differences between strains from these sites have been previously reported, specifically, in larval ethanol tolerance (McKenzie & Parsons, 1974) and in adult starvation resistance after wine seepage feeding (Hoffmann & McKechnie, 1991).…”