Show-Me State Times

Researchers at Saint Louis University have been examining how temperature affects treehoppers, focusing on their thermoregulation behavior. The study, led by Kasey Fowler-Finn and her team, investigated whether these insects regulate their body temperature to maximize reproduction or merely to survive.

“When you look at responses to climate change, the best predictor of responses to climate change is how well you reproduce,” said Fowler-Finn. “So it makes sense that with that thermoregulation, a species should also evolve to maximize reproduction as well as survival. In this paper, Noah was testing exactly that. We asked: Are these treehoppers thermoregulating in order to maximize reproduction or are they only doing so to maximize survival? We found that they're avoiding lethal temperatures and that's about it.”

The research highlighted that treehoppers possess a broad range of livable temperatures but have a narrower range for optimal reproduction. Their investigation included observing the insects in nature and conducting laboratory thermal preference experiments.

Findings revealed that treehoppers engage in thermoregulatory behavior only when necessary, specifically when temperatures reach 36 degrees Celsius. This is significant given the substantial temperature variation—up to 19 degrees Celsius—on a single plant.

“We went into it thinking that they would seek out these microclimates that are really good for mating because it's super important for organisms to mate and produce,” said researcher Leith. “It was surprising and interesting to us that they aren't thermoregulating at all to enhance mating activity; they're mainly only thermoregulating solely to survive, only when it's super stressful and it might cause them to die.”

Fowler-Finn added: “One of the most interesting and significant findings was that there's extreme variation in temperature on a single plant that these animals live on. A single plant can vary nearly 20 degrees celsius. That’s a huge number...and because nearly half of all insect species are plant-living, they could be experiencing those huge variations in temperature."

The study suggests potential consequences for treehopper populations due to climate change limiting suitable mating conditions. “We found that treehoppers are only thermoregulating when they're beyond their lethal limit, which was 36 degrees celsius,” Fowler-Finn explained. “With how variable the climate is...this could cause a shift in their mating patterns...That’s what we’re going to examine next."

Fowler-Finn warns of broader ecological impacts if insect populations decline due to rising temperatures: "A declining population of treehoppers...could create a butterfly effect throughout the environment." Further research is deemed necessary by the team to fully understand these dynamics.