Survival of heat stress with and without heat hardening inDrosophila melanogaster: interactions with larval density

Abstract

SUMMARYSurvival of a potentially lethal high temperature stress is a genetically variable thermal adaptation trait in many organisms. Organisms cope with heat stress by basal or induced thermoresistance. Here, we tested quantitative trait loci (QTL) for heat stress survival (HSS) in Drosophila melanogaster, with and without a cyclic heat-hardening pre-treatment, for flies that were reared at low (LD) or high (HD) density. Mapping populations were two panels of recombinant inbred lines (RIL), which were previously constructed from heat stress-selected stocks: RIL-D48 and RIL-SH2, derived from backcrosses to stocks of low and high heat resistance, respectively. HSS increased with heat hardening in both LD and HD flies. In addition, HSS increased consistently with density in non-hardened flies. There was a significant interaction between heat hardening and density effects in RIL-D48. Several QTL were significant for both density and hardening treatments. Many QTL overlapped with thermotolerance QTL identified for other traits in previous studies based on LD cultures only. However, three new QTL were found in HD only (cytological ranges: 12E-16F6; 30A3-34C2; 49C-50C). Previously found thermotolerance QTL were also significant for flies from HD cultures. Supplementary material available online at

Heat stress survival in the pre-adult stage of the life cycle in an intercontinental set of recombinant inbred lines ofDrosophila melanogaster

“…The two Xlinked QTL were also identified as QTL for viability in the QTL mapping of controls. However, co-localization of these QTL in larvae with QTL for heat resistance in adults (Rand et al, 2010;Arias et al, 2012) suggest that X-linked QTL may affect heat-stress resistance in larvae, because of either linkage or pleiotropic effects on viability and thermotolerance. The genetic basis for thermal adaptation and evolution in holometabolous insects such as Drosophila should depend on the number, effects and chromosomal distribution of QTL across the whole life cycle.…”

“…Recent studies have used this technique in adult D. melanogaster to identify genomic regions in which relevant loci for adaptive change in thermotolerance are localized, with QTL found on all three major chromosomes (Norry et al, 2004;Morgan and Mackay, 2006;Norry et al, 2007a;Norry et al, 2007b;Norry et al, 2008;Arias et al, 2012). Putative candidate genes have been identified and discussed elsewhere (e.g.…”

“…These RIL were previously used to map thermotolerance traits in adult flies (Norry et al, 2008;Arias et al, 2012). However, it is not known whether previously identified QTL for KRHT in adults affect also heat-stress survival in larvae or whether different QTL are affecting heat resistance in this pre-adult stage of the life cycle.…”

Genetic variation for egg‐to‐adult survival in Drosophila melanogaster in a set of recombinant inbred lines reared under heat stress in a natural thermal environment

“…() for a QTL mapping in the laboratory. These lines allowed identification of QTL for diverse thermotolerance traits in adult flies in the laboratory (Norry et al., ; Arias et al., ), as well as for egg‐to‐adult survival (EAS) under heat stress in the laboratory (Sambucetti et al., ). In addition, RIL are useful resources for QTL mapping of heat‐stress resistance in both laboratory and field assays because the nearly homozygous lines can be examined in multiple environments.…”

Patterns of longevity and fecundity at two temperatures in a set of heat-selected recombinant inbred lines of Drosophila melanogaster

“…These RIL were derived from lines artificially selected for high and low knockdown resistance to high temperature (KRHT), which were previously used to map thermotolerance traits in adult flies (Norry et al 2008;Arias et al 2012). Two main aims were addressed in this study.…”