High developmental temperature leads to low reproduction despite adult temperature

Abstract

Phenotypic plasticity can help organisms cope with changing thermal conditions and it may depend on which life-stage the thermal stress is imposed: for instance, exposure to stressful temperatures during development can trigger a positive plastic response in adults. Here, we analyze the thermal plastic response of laboratory populations of Drosophila subobscura, derived from two contrasting latitudes of the European cline. We measured reproductive performance through fecundity characters, after the experimental populations were exposed to five thermal treatments, with different combinations of developmental and adult temperatures (14°C, 18°C, or 26°C). Our questions were whether (1) adult performance is changed with exposure to higher (or lower) temperatures during development; (2) flies raised at lower temperatures outperform those developed at higher ones, supporting the "colder is better" hypothesis; (3) there is a cumulative effect on adult performance of exposing both juveniles and adults to higher (or lower) temperatures; (4) there is evidence for biogeographical effects on adult performance. Our main findings were that (1) higher developmental temperatures led to low reproductive performance regardless of adult temperature, while at lower temperatures reduced performance only occurred when colder conditions were persistent across juvenile and adult stages; (2) flies raised at lower temperatures did not always outperform those developed at other temperatures; (3) there were no harmful cumulative effects after exposing both juveniles and adults to higher temperatures; (4) both latitudinal populations showed similar thermal plasticity patterns. The negative effect of high developmental temperature on reproductive performance, regardless of adult temperature, highlights the developmental stage as very critical and most vulnerable to climate change and associated heat waves.

Long-term evolution experiments fully reveal the potential for thermal adaptation

“…Drosophila subobscura is a species that shows evolutionary responses to climatic factors with repeatable clines of body size (Huey et al 2000;Gilchrist et al 2004) and chromosomal inversions (Prevosti et al 1988) that track global warming (Balanyá et al 2006;Rezende et al 2010). As expected, this species has also been found to respond plastically to thermal challenges (Fragata et al 2016;Simões et al 2020;Santos et al 2021a). Our team has been studying how populations of this species evolve under an increasingly warmer environment (Santos et al 2021c).…”

Warming During Embryogenesis Induces a Lasting Transcriptomic Signature in Fishes

“…Although the same relationship remains to be tested in fish, the increase in entropy caused by developmental exposure to elevated temperature could have similar effects on fitness. Drosophila subobscura incubated at elevated temperatures throughout juvenilehood show a lower reproductive performance as adults than those incubated in control conditions, regardless of the temperatures experienced during later-life (Santos et al, 2021). Therefore, the link between the embryonic environment and later-life fitness is present in ectotherms, and future studies should probe the potential importance of transcriptional entropy in mediating these effects.…”

Long-term cold selection leads to increased thermal plasticity of male body size and thermal canalization of fecundity inDrosophila melanogaster

“…There are two other hypotheses connecting temperature and fitness in various organisms. The colder-is-better hypothesis predicts individuals reared at low temperatures will have greater fitness than those reared at high temperatures; while the hotter-is-better hypothesis predicts the opposite [27–29]. Despite the studies and hypotheses, a tangible gap persists in the comprehensive understanding of the links connecting temperature, adaptation and plasticity and fitness.…”