Climate shock effects persist for generations, fruit fly study shows

A new paper in Molecular Biology and Evolution, published by Oxford University Press, finds that changes in animal development induced by climate shock persist generations after the initial event. The escalating effects of climate change are likely to, in effect, speed up evolution.

Temperatures on Earth are increasing due to anthropogenic climate change, presenting an evolutionary challenge for many populations. Higher average temperatures and more extreme events such as heat waves will lead to increasingly frequent stressful events that can function as strong evolutionary drivers. Recent work suggests that interactions between DNA sequences and gene regulation could link environmental accommodation with rapid evolution. Yet little is known about how these processes interact in natural genetic backgrounds.

The investigators here conducted laboratory experiments measuring gene expression and gene regulatory responses to heat shock in female fruit flies collected from Spain and Finland (to test responses in arid vs. cold climates), their associations with population variation, and fitness-related changes including the viability and development time of the offspring. They also measured the same characteristics generations later to explore transgenerational inheritance.

The researchers found strong gene expression responses to heat shock in both the arid and cold populations, but the responses were less well-regulated in the cold population. Heat shock negatively affected the viability and development of the initial offspring cohort (eggs laid within two days of heat shock) in both populations, but in the arid population, later offspring cohorts (eggs laid more than 2 days after heat shock) developed quicker than controls, indicating a potentially beneficial physiological response.

Some effects of heat shock on gene expression were still present after three generations, particularly in the arid population, where important regulatory genes showed similar gene expression across generations. Furthermore, in the arid population, descendants of the heat shocked flies continued to develop more rapidly than descendants of controls, indicating that the beneficial physiological responses had been transmitted to the great-great-grandoffspring.

This result, together with the detection of genetic variants in the arid population associated with changes in gene expression, provides important clues as to how stress can impact the evolutionary process.

The transgenerational effects in gene expression and development time we observed demonstrate that stress might not only select for better adapted flies, but could facilitate evolution. Understanding why some variants can respond transgenerationally better than others could be important in identifying at-risk populations as the Earth's climate continues to change."

Ewan Harney, paper's lead author