Reaction norms for developmental time and weight at eclosion in Drosophila mercatorum

Abstract

We determined reaction norms for developmental time and weight at eclosion for 2 isozygous and 11 genetically mixed strains of Drosophila mercatorum in four culture media differing in yeast concentration. With decreasing yeast concentration, development was delayed, the weight of emerging flies decreased, and the phenotypic variance of both variables increased. Differences among stocks and significant stock x yeast interactions indicated genetic variance for both variables within environment and different phenotypic responses of stocks across environments. The phenotypic correlation between developmental time and weight was negative at low yeast concentrations and disappeared gradually with increasing yeast. The comparison of completely homozygous with genetically heterogenous stocks showed that most of the increase of variability with deteriorating environment was due to the changing expression of genetic variance. The genetic correlation between developmental time and weight turned from negative in poor to positive in rich medium, while the environmental covariance was negative in all media. Plotting the reaction norms in the developmental time-weight plane rather than separately for each trait reveals most of these results at a glance. It also suggests that much of the genetic variance might be additive, because an effect of the half-sib family structure inherent in the design is clearly visible in the plot. We interpret the pattern of changing variances and covariances, pointing out that the special growth physiology of Drosophila and the way environmental factors affect it must be taken into account. We briefly discuss the implications of changing genetic correlations among traits for the evolution of phenotypic plasticity in general.

Genetics of life history in Daphnia magna. I. Heritabilities at two food levels

“…Heritability differences between environments have been described for birds (van Noordwijk, 1988;Henrich, 1989), and fruit flies (Gebhardt & Stearns, 1988). Explanations for such differences have been proposed (e.g.…”

Stress temperatures and quantitative variation in Drosophila melanogaster

“…Rearing under stressful conditions has been shown to increase phenotypic variation in developmental time (Parsons, 1961;Gebhardt & Stearns, 1988, 1992, dry weight at eclosion (Gebhardt & Stearns, 1988), thorax length (Robertson, 1960;Imasheva et al, 1997), wing length (Tantawy & Mallah, 1961;David et al, 1994;Lazebny et al, 1996), ovariole number (Delpuech et al, 1995), and sternopleural chaeta number (Parsons, 1961;Imasheva et al, 1997). Types of stress used were extreme temperatures (Parsons, 1961;Tantawy & Mallah, 1961;David et al, 1994;Imasheva et al, 1997), deficient larval diet (Robertson, 1960;Gebhardt & Stearns, 1988, 1992, and larval crowding (Parsons, 1961;Lazebny et al, 1996).…”

“…However, the effect of stress on genetic variation is under dispute (Barton & Turelli, 1989) as the available evidence is less clear-cut and the results are often inconsistent (see, e.g. Murphy et al, 1983;Gebhardt & Stearns, 1988, 1992.…”

Environment-dependent trade-offs between ectoparasite resistance and larval competitive ability in the Drosophila–Macrocheles system

“…Yet, when genotype-environment interactions are taken into consideration, context-dependent genetic correlations are often detected among lifehistory traits (Service and Rose, 1985;de Jong, 1990;Stearns et al, 1991). Varying environmental conditions, such as temperature and resource availability, have been shown to generate a change in the direction and/or magnitude of correlations between life-history traits not involving resistance (Service and Rose, 1985;Gebhardt and Stearns, 1988;Reznick et al, 2000;Rigby et al, 2002;Messina and Fry, 2003;Sgrò and Hoffmann, 2004). Environmental stressors in also modify the expression and magnitude of costs of resistance among plantpathogen associations (see Bazzaz et al, 1987;Bergelson and Purrington, 1996;Sandland and Minchella, 2003).…”