Evolution of sex‐specific heat stress tolerance and larval Hsp70 expression in populations of Drosophila melanogaster adapted to larval crowding

Abstract

The ability to tolerate temperature stress is an important component of adult fitness. In holometabolous insects like Drosophila melanogaster, adult stress resistance can be affected by growth conditions experienced during the larval stages. Although evolution under crowded larval conditions is known to lead to the correlated evolution of many adult traits, its consequences on adult heat stress tolerance have not been investigated. Therefore, in the present study, we assessed the adult heat stress tolerance in populations of D. melanogaster adapted to a stressful larval crowding environment. We used replicate populations of D. melanogaster, selected for adaptation to larval crowding stress (MCUs), for more than 230 generations, and their respective controls (MBs). Larvae from selected and control populations were grown under crowded and uncrowded conditions, and their adult heat shock resistance at two different temperatures was measured. Further, we compared Hsp70 expression in crowded and uncrowded larvae of both populations and also measured the Hsp70 expression after a mild heat treatment in adults of selected and control populations. Our results showed that adaptation to larval crowding leads to the evolution of Hsp70 gene expression in larval stages and improves adult heat stress tolerance ability in males, but not in females.

Uric acid metabolism modulates diet-dependent responses to intraspecific competition in Drosophila larvae

“… 7 , 16 , 17 , 18 , 19 Studies in Drosophila melanogaster have been invaluable in uncovering the plastic responses to larval crowding. For instance, larvae developing in crowded conditions have upregulated expression of heat-shock proteins in response to the stress of the developmental environment, 20 , 21 , 22 which may be involved in a hormesis-like response that leads to increased lifespan and fitness benefits in broader ecological contexts. 21 , 23 , 24 , 25 …”

Consequences of adaptation to larval crowding on sexual and fecundity selection in Drosophila melanogaster

“…Moreover, other fitness related traits, especially those related to reproduction such as courtship frequency, mating and reproduction (Shenoi, Banerjee, et al, 2016) have been shown to be in favour of crowded males, or not different. Further, crowded males do better than control males (under crowding) in other life‐history traits such as immune response (Kapila, Kashyap, Poddar, et al, 2021), heat‐shock response (Kapila, Kashyap, Gulati, et al, 2021) and longevity (Shenoi, Ali, & Prasad, 2016). While we cannot completely rule out the possibility that body size influences mating and reproductive success in our experiment, the small difference in size and evolution in other life‐history traits point to the evolution of mating and reproductive success, rather than a by‐product of differing body sizes.…”

“…Since larval crowding scenarios are common in nature and are known to affect adult traits (Bierbaum et al, 1989; Kapila, Kashyap, Gulati, et al, 2021; Kapila, Kashyap, Poddar, et al, 2021; Roper et al, 1996; Shenoi, Banerjee, et al, 2016), the effect of larval crowding and evolution under crowded larval environments on sexual selection is an important avenue of research. Crowding is especially important in holometabolous insects such as Drosophila , where adults lay eggs in ephemeral habitats and juveniles are largely restricted to compete at the egg‐laying sites (Atkinson, 1979).…”

“…Often, populations may be subjected to larval crowding over multiple generations. Larval crowding can generate stressful environments (Mueller et al, 1991; Prasad & Joshi, 2003) and impose selection not only on the larval but also the adult stages (Kapila, Kashyap, Gulati, et al, 2021; Kapila, Kashyap, Poddar, et al, 2021; Shenoi, Ali, & Prasad, 2016; Shenoi, Banerjee, et al, 2016). Recent studies show that sexual selection may impede adaptation to novel environments (Chenoweth et al, 2015), or environmental changes leading to maladaptation can disrupt how sexual selection acts (Martinossi‐Allibert et al, 2017, 2018).…”

Biotic, abiotic and genetic perturbations in genetically variant Caenorhabditis elegans

“…For instance, the adaptation to larval crowding by Hsp-70 expression improved the heat-stress tolerance of D. melanogaster. The studies provided insight on how pre-adult conditions influence the heat stress response and affect adult fitness [14]. The two examples of important model organism-abiotic perturbation helped to understand the adaptation to heat stressed environments at different phenotypic levels, like organismal growth and lifespan.…”