Genetic and environmental factors in the resistance of Drosophila subobscura adults to high temperature shock

Abstract

We have carried out two equivalent selection experiments to increase and decrease heat shock resistance of Drosophila subobscura adults, using an indirect selection method that avoids excessive consanguinity. Heat shock was 33±0.5 °C at saturation humidity. Control lines showed a rapid change of the physiological trait as a consequence of laboratory culture conditions, expressed as a decrease both in heat shock resistance and in the initial population variability for heat shock resistance. Thus, this reduction of variability seems to consist in the loss of those combinations of genes that confer high resistance to heat shock. After eight generations of selection, the selected lines were differentiated from their respective control lines, and the selection response obtained was similar in "resistant" and "sensitive" lines. Differences in survival of progeny of reciprocal crosses between selected lines suggest that inheritance of heat resistance may depend in part on the origin of egg cytoplasm.

Hormesis-like effect of mild larval crowding on thermotolerance inDrosophilaflies

“…Consistent with previous studies (Quintana and Prevosti, 1990;Bubli et al, 1998;Sørensen and Loeschcke, 2001;Arias et al, 2012), heat tolerance was superior in MD larvae compared with that in LD larvae, whereas this increase was less obvious in HD larvae. In parallel, cold tolerance was enhanced in MD and HD larvae compared with that of LD larvae, but the inter-replicate variance was high in individuals from HD conditions.…”

“…In the wild, crowding occurs in ephemeral and isolated habitats; for example, rotting fruits, where fruit fly larvae are forced to cope with multiple stressors, including thermal stress (see Feder et al, 1997;Warren et al, 2006). Several authors have reported that heat stress tolerance could be promoted by crowding in Drosophila adults (Quintana and Prevosti, 1990;Bubli et al, 1998;Sørensen and Loeschcke, 2001;Arias et al, 2012), while other studies reported no effect (Oudman et al, 1988) or even decreased stress tolerance (Loeschcke et al, 1994). These discrepancies may result from different methodological approaches among studies, and from the focus on adult stage despite the fact that crowding occurs at the larval stage and thus primarily affects larvae.…”

“…Hypotheses to explain the promoting effect of crowding on heat tolerance are diverse. For example, Quintana and Prevosti (1990) proposed the existence of a close pleiotropism between lifespan traits and thermal stress traits, Bubli et al (1998) suggested that metabolic alterations could be responsible for enhanced heat knockdown resistance at high densities, and Loeschcke et al (1994) argued that size/surface ratio variations may affect thermotolerance. Sørensen and Loeschcke (2001) first tested the existence of mechanistic links between crowding and thermal stress tolerance.…”

Genetic variation for resistance and acclimation to high temperature stress in Drosophila buzzatii

“…Although genetic variation for resistance to rapid temperature increase has been identified previously by selection in D . melanogaster (Morrison & Milkman, 1978) and D. subobscura (Quintana & Prevosti, 1990), flies were not pretreated in those experiments. Therefore those results may have been affected by different factors, such as the temperatures at which heat shock genes are transcribed, or by factors other than the heat shock system, which may not be activated quickly enough in some individuals exposed to a very rapid temperature increase.…”

“…Collin (Quintana & Prevosti, 1991). However, variation among populations has not been examined (Huey & Bennett, 1990), although Parsons (1980a) found that D. melanogaster and D. simulans Sturtevant from Melbourne, Australia were more tolerant to temperatures of c. 34-35°C and to desiccation than were those from Townsville.…”